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Renovation of Buildings Having Damp and Salted Walls – Case Analyses

Renovation of Buildings Having Damp and Salted Walls – Case Analyses Acta Sci. Pol. Architectura 20 (2) 2021, 51–64 content.sciendo.com/aspa ISSN 1644-0633 eISSN 2544-1760 DOI: 10.22630/ASPA.2021.20.2.14 ORIGINAL P APER Received: 18.12.2020 Accepted: 24.03.2021 RENOVATION OF BUILDINGS HAVING DAMP AND SALTED WALLS – CASE ANALYSES Wacław Brachaczek Faculty of Materials, Civil and Environmental Engineering, University of Bielsko-Biala, Bielsko-Biała, Poland ABSTRACT This article discusses the issue of renovation of buildings having damp and salted walls. The results of conservation research on the walls of two historical buildings from the beginning of the 20th century are presented. It was determined that the walls of the buildings are burdened with moisture and salts. The use of traditional cement and limestone plaster for renovation of such walls, due to their low diffusivity, is a tempo- rary and short-term solution. A suitable material is a renovation plaster, which should be selected depending on the properties of the wall. Various approaches to the renovation of these two buildings were presented. Where moisture was caused by capillary rise, the moisture barrier was first restored and a system of renova- tion plasters consisting of rough coat, undercoat plaster, hydrophobic plaster and paint coating was used. In the second case, due to only a partial replacement of the plasters, after protection of the facade against rainwa- ter, the plasters will be supplemented with renovation rough coat and hydrophobic renovation plaster. Before applying the paint coating, the entire surface will be covered with a renovating lime putty. Key words: renovation plasters, salts in walls, moisture in walls the walls will dry out. Walls with considerable thick- INTRODUCTION ness which are protected against water may dry out In the renovation of historic buildings having damp for many years under natural conditions. If the drying and salted walls, repetitive treatments leading to a per- procedures are not carried out in an appropriate way, manent reduction in the level of moisture in the walls the damp wall containing salts will continue to be can be distinguished. The procedures are based on the destroyed and degraded. While technologies for con- sequence of operations: source identification → root ducting renovation treatments are known and widely cause removal → repair. Walls are considered dry if used, there is no single universal method which can their mass humidity is at the level of 3–6%. The basic be used for most historic buildings (Charola, 2000). technological renovation activities are related to the The selection of comprehensive technological solu- restoration of horizontal and vertical damp proof in- tions leading to the reduction of the mass humidity sulation, solving the problem with salts, repairing the of walls is still controversial. One method used for walls and refurbishing the facade elements to restore different buildings may sometimes bring different re- aesthetic value (Brachaczek, 2018a). Subsequent op- sults. The reasons for this are manifold. The choice of erations are performed to reduce the dampness of the a technological solution is influenced by many factors walls. Limiting renovation work merely to a restora- ranging from the degree of moisture or salts content tion of moisture barriers only does not guarantee that to the workmanship. The reason may be restrictions Wacław Brachaczek https://orcid.org/0000-0002-4782-8409 wbrachaczek@ath.bielsko.pl © Copyright by Wydawnictwo SGGW Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 related to the condition of the walls or the properties of salt by way of advection or dispersion. It occurs in of the materials which they are made of. Modern re- higher parts of walls with lower humidity, when, as pair materials happen to react with the wall substance, a result of evaporation, the moisture in the outer layer which leads to unexpected effects such as swelling or of the wall is successively enriched with a greater loosening. Further restrictions are related to the very amount of salt ions in relation to the moisture inside method of performing renovation works. Often, the the material. The salt ions will then move towards need to preserve original design solutions does not a lower concentration environment, i.e. opposite to enable performing certain treatments effectively. In the direction of drying (Petković, Huinink, Pel, Ko- particular, these are the situations related to moisture pinga & van Hees, 2010). Under natural conditions, protection of hard-to-reach places that, due to their as a result of alternating damping and drying of walls, unique nature, must be left intact. When drying walls, salts present in the pores undergo cyclic dissolution too rapid removal of moisture may sometimes cause and crystallization. This results in the destruction of damage to the substance of the walls and losing their the wall structure due to the generated crystallization strength due to the capillary forces in the pores. pressure affecting the pore walls of building materials The impact on the nature of the salt-induced dam- (Brachaczek, 2018a). age to the walls depends on the materials and the ex- Regardless of the way the salts enter the walls, they posure of the wall elements. Salts may be accumulated dissolve in contact with water. Due to their concentra- in dry walls for decades and only to a slight degree tion, such solutions may be unsaturated or supersatu- contribute to the damage. The damage is the most se- rated. The supersaturated solution can be found in the vere in damp walls. Salts are crystalline substances, porous structure of building materials if moisture to- easily soluble in water. The most dangerous salts in- gether with the salts dissolved in it continuously pen- clude: sodium, potassium, magnesium and calcium etrates into the walls, and then evaporates in the higher chlorides, nitrates and sulphates. Nitrates occur in the parts of the wall. As the moisture evaporates the salt external environment as products of biological oxida- concentration in the pores increases. This phenome- tion of organic compounds or come from agricultural non is accompanied by an increase in the viscosity of fertilizers. The sources of sulphates in urban areas the solution, and thus a reduction in the rate of mois- are flue gases emitted by the combustion of hard coal ture transport by way of advection. With the gradual and liquid fuels. The occurrence of chlorides can be increase in salt ion concentration, the solubility limit associated with the use of de-icing agents for pave- of the solution is exceeded. As a consequence, ther- ments and roadways. All of these salts can be found in modynamically unstable supersaturated solutions are groundwater (Lubelli, van Hees & Groot, 2006; Hall formed, spontaneously striving to transform into satu- & Hoff, 2007). rated solutions by precipitating excess substance in the The moisture problem applies to most historic form of crystals. As a result of the linear growth of buildings. The most common cause of penetration of crystals from the supersaturated solution, an increase walls by the salt is damage or lack of waterproofing in hydrostatic pressure is observed, which is due to the protection of the walls against moisture from the side increase in the total volume of the crystals and the so- of the ground. In this case, salt transport is the result of lution relative to the volume of supersaturated solution capillary rise of solutions through the micropore sys- before crystallization. The hydrostatic and/or crystal- tem present in building materials (Gorecki & Wyrwał, lization pressures generated in this way may exceed 2010). It can be carried out by means of advection (salt the tensile strength of the material, causing its destruc- transport), dispersion and diffusion (due to salt con- tion. As a result of this mechanism a degradation of centration gradient). As a result of the advection, salts plasters and walls in the moisture zone progresses, salt and moisture are transported towards the outer sur- efflorescence occurs, plasters and paints peel off (Pav- face. The transport by means of advection and disper- líková, Pavlík, Keppert & Černý, 2011). In addition, sion occurs with considerable moisture content. Dif- the dampness of the walls affects the unfavourable fusion is a phenomenon competitive to the transport microclimate of rooms, contributes to the infestation 52 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 of the building by mould fungi or insects, which may pair materials. An example would be mistakes made result in health problems. It also reduces the thermal during reconstruction of horizontal moisture barriers by injection. It happens that injections are performed insulation of the wall. The effectiveness of renovation works on build- improperly in cracked walls containing voids without ings with salted and damp walls depends on proper pre-injection. The pre-injection consists in pre-filling diagnostics and cooperation of specialists qualified holes with sealing mortar, whose task is to fill gaps in specific fields (designers, contractors and technol- and voids in the wall. Another mistake is making injections in stone walls. Holes are often drilled in ogy providers). Partially, the principles of this process are described in the WTA 4-5-99/D instruction titled stones with low absorbency, while moisture as a re- “Evaluation of masonry” (Wissenschaftlich-Tech- sult of capillary rise moves in the joints. In such cases nische Arbeitsgemeinschaft für Bauwerkserhaltung the injection is ineffective because the injected filler und Denkmalpflege e.V. [WTA], 1999). However, cannot penetrate the wall. Another factor affecting the durability of renovation works is the inadequate way due to the complexity of the problem and the devel- opment of new technologies, this instruction can be of conducting plastering works. Occasionally, after a valuable guideline and needs to be combined with restoring moisture barriers, plastering works are car- professional and specialized knowledge. To renovate ried out using traditional lime and cement mortars. In historic buildings, it is necessary to recognize the most cases, such mortars not only limit drying walls due to low diffusion relative to water vapour, but nature and properties of the materials used. After de- tailed testing, materials working well with the original they can also contribute to a serious deterioration of material and thus facilitating the repair are selected. the historic walls due to the mismatching of plasters Determination of the degree of saltiness and damp- to the substrate. Such situations occur in particular ness of walls is only one of the necessary tests (Bajno during renovation. In these cases, the wall is highly varied in terms of strength and has different water ab- & Budnik, 2019). In addition to these, it is also impor- tant to determine other properties, such as the strength sorption. Fresh, thin mortar applied to old walls will of the original materials, sorption coefficient, density, dry quickly. Also the hydration of cement proceeds microstructure of pores, bricks and joints. The devel- quickly, which may result in a significant shrinkage. opment of technologies and materials for the renova- This is when the mismatch between the plaster and the substrate becomes evident. Restricting the free- tion of historic buildings with salted and damp walls was especially pronounced in restoring moisture bar- dom of deformation for these materials generates high riers. The choice of a way of restoration of horizontal tensile stresses in the plaster layer. However, if the insulation depends on the structure of the walls, their plaster yield point is exceeded, it will crack. In broad thickness and, above all, their condition (Brachaczek, outline, it can therefore be pointed out that the shrink- age of plaster layers on the rigid substrate would be 2018b). The buildings have often been rebuilt many times over the centuries, and they have been modern- the direct cause of cracks in a direction normal to the ized and renovated according to the knowledge and substrate. Most traditional plastering mortars are char- technology corresponding to the given era. Cracks acterized by high drying shrinkage and low flexibility and crevices often occur in historical walls, and also which makes them completely useless in renovation works, and their use is even harmful to walls. Special affects the selection of the appropriate method. Due to the thickness of the walls, the chemical injection plaster mixtures modified with plasticizing admix- method is often used to reconstruct moisture barriers. tures (polymers) are suitable for such substrates. Ad- Despite the fact that the modern building materials mixtures based on natural and artificial polymers are enable carrying out works so as to prevent further de- of particular importance here. The improvement is in struction of the walls, a number of mistakes are made the amount of shrinkage, flexibility and adhesion to during the works. Errors can be made at any stage of the substrate and aggregates, water retention, etc. The renovation, resulting in negative opinions about the addition of polymer modifiers to cement mixes im- innovative technological solution or innovative re- proves flexibility of the plasters. As a result, their sus- architectura.actapol.net 53 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 ceptibility to shrinkage cracks is reduced. The most buildings come from the beginning of the 20th cen- suitable material for carrying out plastering works on tury. They were built on a site where originally one- -storey buildings, probably from the turn of the 18th salted and damp walls are renovation plasters. Renovation plasters are intended for damp and salt- and 19th centuries, were located. In both cases, reno- ed walls. These are porous plasters characterized by vation plasters were used for restoration. However, high resistance to salt. Most manufacturers do not offer due to the varying salt and moisture contents in these only a single product but several mortars constituting buildings, different approaches to renovation were presented. a renovation plaster system. Such a system includes: renovation rough coat, renovation undercoat plas- ter, hydrophobic renovation plaster, renovation putty MATERIAL AND METHODS and paint coating. The properties required for such plasters are included in the PN-EN 998-1:2016-12 Study objects The first building – called the Under the Frogs – is standard titled “Specification for mortars for masonry. Part 1: Plastering mortar” (Polski Komitet Normaliza- a tenement house at 12 Wojska Polskiego Square in cyjny [PKN], 2016). In the standard, only the proper- Bielsko-Biała. The tenement house was built in the Art ties of hydrophobic renovation plaster for damp and Nouveau style, and, in addition to the apartments, once salted walls are specified. The issue of renovation housed a well-known winery of Rudolf Nahowski. The house has an irregular shape piled up at the corner plasters is more widely addressed in the WTA 2-9- -04/D instruction titled “Renovation mortar systems” into a high tower. The top floors are decorated with (WTA, 2004). This document does not refer to a sin- imitation of half-timbered wall made of plaster. The gle product, but to a renovation plaster system whose half-timbered wall decoration is also visible on the components have the right properties and are com- level of the third floor on the facade from the side of the Wojska Polskiego Square. At the top of the roof, patible with each other. Although renovation plaster systems have been used for several decades, and in a forged structure with fancifully curled elements, many cases the benefits of using them are obvious, to which winery advertising was attached, was pre- there were also some critical opinions. The reserva- served. Windows with various patterns were arranged tions concerned the adverse impact on wall structure. asymmetrically. The northern wall is decorated with a portal crowned with figurines of two frogs of which In some cases, it has been observed that damp walls covered with renovation plasters tend to retain mois- one holds a mandolin and the other a long pipe in one ture what resulted in the plaster peeling off in winter. hand and a wine glass in the other, resting its elbow on As a consequence, historic building conservators have a barrel, most probably full of wine (Fig. 1). increasingly refrained from using renovation plasters. The second building is located at 2 Waryńskiego Street. It is characterized by a traditional layout of the In some European countries, administrative authori- ties responsible for the protection of cultural heritage block derived from the neoclassical pattern. It consists began to prohibit the use of these materials on historic of a massive rusticated plinth covering the ground buildings. In Poland, the main problems which con- floor. The building has refined flat facades, crowned tractors face are related to the appearance of salt efflo- with a line of strongly shading prominent eaves cor- nice, supported on stone brackets. The walls stand out rescence, the appearance of scratches and cracks, low cohesion, difficulties with application and processing. with their delicate ornamentation of window frames in Although the problems of using renovation plasters the form of wreaths, which makes the whole structure is a topic of constant discussion, it can be concluded seem light. The ground floor with rectangular win- that the reasons for these shortcomings can be seen in dows creates an oblong-shaped plinth with elongated the inadequate matching of renovation technology and rustications. Higher floors with windows framed in materials to the properties of the restored walls. plaster, arranged symmetrically along with the portal This paper presents different approaches to reno- constituting the entrance door frame enhance the im- vation of two buildings from a similar period. Both pression of orderliness and peace. 54 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Fig. 1. The front wall of the “Under the Frogs” house at Wojska Polskiego Square (on the left), tenement house at 2 Waryńskiego Street (on the right) in Bielsko-Biała Under the eaves, there are wreath-shaped decora- colour. In the places where capillary rise occurred, tions. The neoclassical roof with a slight inclination as a result of previous renovation works, the plasters contributes also to lightness of the building, which were replaced with cement and cement-lime plasters. makes it stand out among other tenements. The north- Stucco details were either made of lime mortar or -eastern facade of the building with a wooden floor were plaster casts. They were covered with a layer of balcony and a forged iron railing and brackets closes lime gesso. Inside the building there are stone plinths a string of tenement houses built on the embank- of white marble. ment. Above the roof covered with steel sheet there are huge brick chimneys covered with plaster, while Measurements the walls above the ground are made entirely of full Diagnostic examinations of the walls included visual brick. The building has a partial basement. The floors inspection of the facade as well as determining the level of the non-basement part are made of concrete on of moisture and salt saturation of the walls at the exter- bedding. The basement walls are made of bricks and nal facade and basement walls. Moisture testing of the natural stone and are covered from the inside with masonry was performed using a non-invasive method, cement and lime plaster. The ground floor is vaulted, using Protimeter Surveymaster and Trotec T3000 the upper floors are covered with faceted beam ceil- hygrometers. For this purpose, holes were drilled at ings with sound boarding. Inside the building there heights of 10, 50, 100 and 150 cm from ground level, is a prominent staircase with block steps mounted to a depth of approx. 10 cm. When determining the to the stringers and the staircase wall. The first and vertical lines in which the measurements were read, second floor plasters were made of lime mortar. The equal distances between them were kept. These lines original rustication at the ground floor level and the were routed so as to avoid obstacles. inter-story cornice above the ground floor are made The level of concentration of harmful salts was of strong, dark beige mortar in the dark sandstone determined based on samples of plasters, bricks and architectura.actapol.net 55 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 mortars taken from the central part of the walls on RESULTS AND DISCUSSION each side of the building using a low-speed drill. In Moisture and salt content particular, wall sections degraded to the greatest ex- To determine the degree of moisture, the classifi- tent were examined. The concentration of chlorides, cation for brick walls in accordance with PN-EN ISO sulphates and nitrates was analysed. The tests were 12570:2002 standard (PKN, 2002) was used. The carried out in accordance with the guidelines of the measurement results are presented in Tables 1–3. Ac- WTA 2-9-04/D instruction. The tests on the samples cording to WTA 4-5-99/D in terms of the dampness of were carried out in the laboratory of Sempre Farby the walls, the following division is applied: a wall with company. Table 1. The results of moisture content in walls by weight [%] for the house at 2 Waryńskiego Street Front wall (south-east) Measurement height [cm] 150 14.4 12.6 2.4 2.4 2.6 1.5 11.1 4.3 3.1 100 12 22 11.2 10.9 4.8 4 5 4 3.1 50 10.6 17.2 16.3 9.3 5.5 6 8 14 5.5 0–10 5.5 18.6 13.6 15.9 22 22 16.2 17 3 dry wall wall with increased humidity wall with an average humidity very humid wall wet wall Table 2. The results of moisture content in walls by weight [%] for the house at 2 Waryńskiego Street Sidewall (north-east) Rear wall (north-west) Measurement height [cm] 150 3.4 16.6 10.7 17.8 4.4 18.7 22 100 5.5 4.6 22 9.9 14 5.5 5.8 50 3.8 4.2 9.9 11.3 18.3 3.1 22 0–10 3.6 19.8 13.9 22.0 8.8 19.0 5.7 wall with increased humidity wall with an average humidity very humid wall wet wall Table 3. The results of moisture content in walls by weight [%] for the house at 2 Wojska Polskiego Square from Wojska Polskiego Square from 2 Targowa Street Measurement height [cm] 123123 4 150 1.6 1.7 12.3 1.8 1.6 1.6 5.5 100 3.5 1.7 3.5 1.8 1.8 1.6 1.8 50 2.1 2.5 1.7 8.9 1.9 1.6 1.7 dry wall wall with increased humidity wall with an average humidity very humid wall 56 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 an acceptable mass humidity not exceeding 3%, a wall the wall, as well as the effects of defrosting agents. with increased humidity with humidity of 3–5%, a Building facades from the side of Targowa Street wall with an average humidity of 5–8%, very humid were renovated in the 1990s. The facade from the side 8–12% and wet with mass moisture above 12%. of Wojska Polskiego Square was renovated several The measurement results of the salt content are times, as it was determined based on the stratigraphic presented in Tables 4–5. To determine the degree of studies. the salt content, the classification for brick walls in The building’s facades are in very poor condition, accordance with the WTA 2-9-04/D instruction was both in terms of technology and aesthetics (Fig. 3). used. According to this classification the following Roof eaves, cornices under and over the windows are division is used in respect of the salinity of the walls: secured with flashings or plain tiles. Flashings are a wall with a low salt content, a wall with a moderate damaged, cracked, deformed, and do not fulfil their salt, and a wall with the high salt content. protective function. Lack of protection against water Based on the testing and examinations carried out, caused the mortar to be washed out, loosening strong it can be concluded that the facades of both buildings compact parts of stucco elements. There are numerous are in very poor condition. In the case of the “Under defects on the surface of the cornices, moreover there the Frogs” tenement house, the plinth of the build- are surface peels, stains, salting, cracks, biological ing made of stone is badly damaged (Fig. 2). A direct corrosion. Penetrating and freezing water caused deep cause of plinth damage was splashing rainwater from cracks and peeling off from the surface, individual the street, snow and ice accumulating in this part of loose elements fell off. Table 4. Averaged salt content of the walls of the tenement house at 2 Waryńskiego Street Measurement of salt content and limit values for individual loads by weight [%] loading with salts – limit values Ion type north-western north-eastern south-eastern acc. to the WTA 2-9-04/D wall wall wall low moderate high Chlorides (Cl ) 0 0 0.5 < 0.2 0.2–0.5 > 0.5 2– Sulphates (SO ) 0.2 0.8 0.8 < 0.5 0.5–1.5 > 1.5 Nitrates (NO ) 0.025 0.125 0.125 < 0.1 0.1–0.3 > 0.3 wall with a low salt content wall with a moderate salt content wall with the high salt content Table 5. Averaged salt content of the walls of the tenement house at Wojska Polskiego Square Measurement of salt content and limit values for individual loads by weight [%] salts content – limit values the wall from the wall from Ion type acc. to the WTA 2-9-04/D the Wojska the Targowa Polskiego Square Street low moderate high Chlorides (Cl ) 0 0 < 0.2 0.2–0.5 > 0.5 2– Sulphates (SO ) 0.6 0.4 < 0.5 0.5–1.5 >1.5 Nitrates (NO ) 0.025 0.25 < 0.1 0.1–0.3 > 0.3 wall with a low salt content wall with a moderate salt content wall with the high salt content architectura.actapol.net 57 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Fig. 2. Details of the facade of the “Under the Frog” tenement house at the Wojska Polskiego Square in Bielsko-Biała Fig. 3. Damage to the facade resulting from the impact of rainwater in the “Under the Frogs” tenement house in Bielsko-Biała The destruction of plasters is so great that whole Analysing the results of humidity tests presented fragments of the stucco peeled and fell off. Some stuc- in Table 3, it can be concluded that the moisture level co elements made of thickly applied mortar are con- of the walls building is very uneven. No decrease in nected to the wall with nails and there is a risk that the mass humidity correlated with the height of the they could fall off. Damage caused by water and snow wall was observed. Therefore, it can be assumed that on cornices and the lack of a hydrophobic coating on capillary rise from the foundations side in the walls the surface of the walls caused water to be absorbed is insignificant. With so little moisture, there is no into the plaster and brickwork joints. On the surface need to restore the horizontal moisture barrier. How- of the plasters, stains, moisture, water-soluble salts in ever, the destructive effects of water can be observed the form of efflorescence are visible above the treat- on the building’s facade. The humidity level is high ments, plasters are disintegrated, cracked, detached, in some places. It can therefore be expected that in sanded, with especially severe changes in the lower certain places, as a result of flooding the facade with parts of window bands. Original lime plasters are rainwater, the water content in the walls can be high. heavily weathered and form a crust. In many places When testing the walls for moisture content from the they have become detached from the wall. The main inside, the humidity of the walls did not exceed 3% factors causing damage were: rainwater flowing down by weight. the facade with no flashings, water coming from capil- Analysing the research results of the degree of lary rise and atmospheric pollution. the salt content in the walls presented in Table 5, the 58 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 presence of nitrate and sulphates ions corresponding the front wall directly adjacent to the street. It was also at low to medium content were found. However, no here that the concentration of chloride and sulphates chlorides were found in the walls. Despite the fact was the highest. that the building’s walls are in the immediate vicin- ity of the paved streets, the walls were not loaded Technology and materials used in renovation with chlorides. It should be noted that the plinth of works the building was covered with natural stone cladding In the case of the “Under the Frogs” tenement house, which could protect the walls against the effects of the first scope of renovation works involved inhibiting salts used for de-icing. Based on the examination, it the destructive factors. To this end, in the first stage can be concluded that the stone cladding suffered the of work it is necessary to cut off the supply of water, most due to the influence of external factors, how- both pulled up by capillary rise and flooding facades ever, proved to be an effective protection for this part due to damaged and missing treatments. Fitting the of the walls. missing tiles and reinstalling them in places where In case of the building at 2 Waryńskiego Street, hu- they protected cornices. In the next stage, removal of midity tests presented in Tables 1 and 2 indicated that all secondary elements such as cables, advertisements, the mass humidity distribution in the walls was high. antennas being the source of local moisture penetra- A clear trend of the humidity level decrease along with tion into the walls. The stone pedestal was cleaned of the height of the measurement can be observed on all efflorescence and cement wash – manually or mechan- walls. This indicates the capillary rise of moisture in ically using chisels, hammers and scrapers. All joints the wall and is the result of damaged horizontal insu- were also removed. The stone defects were filled with lation of the building walls or lack thereof. Moisture sealing compound, the joints were filled with grout- is pulled up from the ground by old bricks and mortar ing mortar containing trass. The whole structure was within a capillary system. In addition, an increase in protected with a water-repellent Sempre Aqua protekt humidity in the lower, unsecured vertical insulation preparation based on silicone microemulsion. To re- zone (up to approx. 50 cm above ground level) may construct the stucco details, the Renowator 740 com- come from splashing rainwater. Also, the greatest posite stucco mortar (Sempre) was used. damage in this building was observed in the bottom Since the tenement house is a peculiar piece of ar- part of the plinth and in all places where the flashings chitecture of exceptional historic value, the next stage were significantly damaged and ceased to fulfil their of the renovation will consist in emergency preserva- function (Fig. 4). tion of the facade. The removal of wet, loosened and Analysing the results of salt content in the walls detached plasters has been foreseen. It is planned to presented in Table 4, the presence of chloride, sulphate remove simple plasters in 50%, stucco details in over and nitride ions corresponding to medium content were 30%. The plaster whose condition does not allow found. The highest nitrate concentration was found in structural strengthening and gluing will be removed. Fig. 4. House at 2 Waryńskiego Street, the figure shows the destruction of the walls caused by ground water rise architectura.actapol.net 59 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Well-preserved primary plasters and stucco elements tion combined with pre-injection to restore horizon- will be reinforced with a reinforcing preparation based tal insulation. The pre-injection consists in pre-filling on silicone resins, silicates or fine-molecule silicates holes with sealing mortar, whose task is to fill gaps (tetraethyl silicates), e.g. Renowator 350 by Sem- and voids in the wall. Optionally, in the case of stone pre Farby. As no capillary rise of groundwater from and brick walls with a diverse structure, good effects the foundations was found, the restoration of the hori- are obtained by using gravity injection with an agent zontal moisture barrier was not performed. However, of high consistence. This product contains polysilicate due to the partial moisture penetration in the walls, compounds, well penetrating building materials. They it was decided to replace the removed plasters with form a tight moisture barrier as a result of a change Renowator 545 – hydrophobic renovation plaster for in surface tension of the pores. The advantage of this diffusion plaster rendering. Application of the plaster product is high consistence which facilitates applica- will be preceded by proper preparation of the substrate, tion in walls of high heterogeneity. In order to elimi- consisting in cleaning the wall of dust, dirt and grease. nate the impact of splashing rainwater on the humidity In order to avoid cracks and discoloration on the sur- of the walls, it was recommended to secure the plinth face of the plaster coat, the brittle and weathered joints zone of the walls (at a height of up to 50 cm) with ver- between the bricks will be removed to a depth of 2 cm. tical sealing mortar. Places covered with mosses and algae will be cleaned Due to the considerable destruction of plasters, it with steel brushes and then disinfected with Aglesil was necessary to remove them down to the brick layer. algae remover. In order to reduce the water absorp- Most of the walls were in good condition, however tion before application of the rough coat, the surface they were very wet and salted. The condition of the will be wetted with water. The first plastering layer bricks was very diverse, with some of them strong, will be made of the Renowator 500 renovation coat, and others weak and brittle. The mortar which the which will improve the adhesion of the next layer of joints were made of was largely rotten and brittle. At renovation plaster to the substrate. Unification of the some windows, especially in the upper floors of the facade surface, especially in the places where primary southern facade, cracks of cornices and bands around plasters and renovation plasters are combined, will be the windows could be observed. Due to the high salti- made using Renowator 680 renovation lime coat. The ness and dampness of the walls, higher than in the protective layer will be silicone paint with reduced dirt case of the “Under the Frogs” tenement house, the use adhesion and self-cleaning capabilities (e.g. Sempre of traditional cement and lime or cement plasters for Azzuro). renovation would be a temporary solution. Due to the In the case of the building at 2 Waryńskiego Street, low diffusivity of water vapour, on damp and salted the first scope of renovation work included roof repair walls, such mortars tend to peel away and crack. This phenomenon may be affected by such factors as stress combined with the replacement of roof slopes with window joinery renovation, replacement of flashings caused by salt crystallization, as well as mismatch- together with rainwater drainage system. In order to ing of plaster properties to the substrate. According protect the building against the harmful effects of wa- to Brachaczek (2018b), a single type of renovation ter coming from the ground, it is planned to restore plaster with universal properties should not be used to renovate historic buildings. There is probably no the horizontal moisture barrier by injection. Due to the specific nature of this method, a waterproofing such plaster available anyway. The walls differ in wa- horizontal insulation just above the ground level was ter sorption coefficient, strength, diffusion resistance, planned for all analysed walls, except for possible etc. Whenever choosing plasters, their compatibility pressurized water impact. This will protect the build- with the substrate needs to be checked. Damp walls with a low water sorption coefficient should not be ing parts above the ground against moisture migrating from the ground. The varied nature of the foundations, covered directly with hydrophobic plasters. The low mostly made of stone, and the voids or gaps occur- sorption coefficient of the walls means that the walls ring in it, determined the use of low-pressure injec- dry slowly and the water is stored in them for several 60 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 years. In such cases, only renovation plasters with undercoat plaster, prevents salt from getting outside high water sorption properties may be used for renova- the plaster coat. The thickness of this layer should be tion. In order to avoid the appearance of scratches and 1–2 cm. In order to obtain a smooth, aesthetic surface, cracks resulting from mismatching the plaster strength the facade was covered with a fine-grained vapour- to the substrate, additional compressive and bending -permeable finishing layer of Renowator 580. strength tests as well as sorption tests were carried The proper function of renovation plasters is pos- out in accordance with PN-EN 1015-18:2003, PN-EN sible due to the creation of a suction force causing the 12390-3:2019-07 and PN-EN 12390-5:2019-08 stand- moisture to transfer from the wall to the plaster placed ards (PKN, 2003, 2019a, 2019b). Six brick samples on the wall. This is possible when the plaster water were taken from each side of the building. The aver- sorption coefficient is greater than the one of the brick. aged results are summarized in Table 6. In this case, for the analysed wall materials, the suitable plaster is Renovator 520 undercoat renovation plaster. The sorption coefficient of this plaster is high and it is Table 6. Physical properties of the tested brick greater than the determined wall sorption coefficient –2 –0.5 of 0.3 kg·m ·min . Strengths of renovation rough Tested brick property Value coat, porous and hydrophobic plaster are 4.4, 3.8 and –2 –0.5 3.4 MPa, respectively. They correspond to CSII class Absorption coefficient [kg·m ·min ] 0.26 plasters with a strength of 1–5 MPa. Compared to the Compressive strength [MPa] 5.80 bricks encountered in the building, these plasters have Tensile strength [MPa] 1.79 the lowest strength and should not have a destructive effect on the structure of the walls. This is very im- portant, because in the case of plaster with strength According to the WTA 2-9-04/D instruction, the clearly higher than the material to which it is applied, effectiveness of plasters in wall drying depends on ap- there is a risk of shrinkage leading to the destruction propriate porosity (> 60%) and distribution of pores of the top layer of the brick. Moreover, renovation (the number of capillary and air pores), enabling the plasters containing polymer modifiers have been used capillary transport of moisture, diffusivity (m < 10), for renovation, reducing shrinkage during drying, im- –2 –0.5 surface absorption coefficient w > 1 kg·m ·h . proving plaster elasticity, adhesion to the substrate and The plastering was preceded by preparatory works water retention. consisting in removing fragile and weathered joints to Damaged stucco elements were restored using a depth of 2 cm and supplementing them with fine- Renowator 740 stucco mortar. It is characterized by -grain Renowator 520 renovation undercoat plaster. excellent workability, low shrinkage when drying and The building walls were covered with a system of resistance to weather conditions. In order to insulate renovation plasters with layer thicknesses determined the vertical plinth zone of the building, the lower part on the basis of the WTA 2-9-04 instruction. The wall of the building (up to 50 cm above the ground) was bonding layer was made using a renovation rough cleaned of old plastering down to the brick layer, and coat, which should cover the wall in an openwork pat- then covered with Renowator 300 – two-component, tern, i.e. on 50% of the wall surface, and its thickness highly elastic sealing compound. It protects the cov- should not exceed 0.5 mm. The next layer was made of ered wall against both moisture and rainwater as well Renowator 520 undercoating plaster. The main func- as water penetration. tion of this layer is to store salt. It is characterized by high porosity, high vapour permeability and high water Evaluation of renovation works sorption coefficient. The thickness of this layer should There is a great deal of evidence acknowledging the be between 1–2 cm. Directly on it, Renowator 540 hy- effectiveness of renovation plasters used for renovat- drophobic, vapour-permeable renovation plaster was ing damp walls. The justification of the proposed so- applied. It accumulates salts to a lesser extent than the lutions are multiannual observations of the renovated architectura.actapol.net 61 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Fig. 5. House at Wojska Polskiego Square (on the left), tenement house at 2 Waryńskiego Street (on the right) in Bielsko- -Biała after renovation buildings and the analysis of the cases described in the may be many times higher (Misiewicz, 2016). Another literature (Dudás & Terjék, 2015; Misiewicz, 2016). mistake is too much filling and smoothing, which con- Figure 5 shows the state of elevation at Waryńskiego siderably lowers the permeability of water vapour. Is Street three years after renovation and the elevation of also unacceptable to fill the corroded plaster by using the building called Under the Frogs after a year. materials of different characteristics than the existing In case of the tenement house at Waryńskiego plaster. It is not allowed to apply materials of low per- Street, the dampness of lower than 3% was obtained meability of water vapour, for instance cement finish after three years from renovation. The appointed time (Hughes et al., 2012). is consistent with the results achieved by (Gosztyła, Leś & Sikorski, 2017) in case of the tenement house SUMMARY AND CONCLUSIONS at the main square in Rzeszów, where renovation plas- ters were also applied for renovating damp walls. The Historic buildings are extremely valuable testimony to qualities of the plasters are frequently overestimated. our culture and their renovation should be approached One cannot expect renovation plasters to be effective very individually. Before starting work, as much in- if the source of dampness has not been removed. In formation as possible about the building needs to be such cases the plasters lose their properties as a re- gathered. Successful renovation must be preceded by sult of storing more salt caused by capillary suction, a series of tests to determine the degree and source of which considerably shorter their durability (Dudás & moisture and saltiness. It is also important to examine Terjék, 2015). It is bad practice of some contactors to additional properties of the wall (such as sorption or apply renovation plasters in the dampest spots, as well strength). Only on the basis of these properties reno- as to combine them with lime-cement of low perme- vation plasters can be selected so as to prevent water ability of water vapour. In this case the wall still re- retention in the walls and the destruction of the sub- mains damp and the dampness in the lime-cement area stance which they are made of. The material solutions 62 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Dudás, A. & Terjék, A. (2015). Efficiency assessment of proposed in the study are optimal for the analysed posterior waterproofing systems of renovated porous wall. In each case, however, the same materials were limestone masonry work. Tehnički vjesnik – Technical used according to a different technology. Application gazette, 22 (5), 1225–1236. https://doi.org/10.17559/ of hydrophobic renovation plaster without the prim- TV-20140715083036 ing layer of salt-accumulating plaster to a wall with Gorecki, P. & Wyrwał, J. (2010). Proces niszczenia murów significant humidity and high load, may hinder dry- ceglanych w zabytkowych budynkach i obiektach prze- ing the wall. In this case, when the water dries and mysłowych [Degradation process of old brick walls in evaporates, the salts will crystallize and accumulate in monumental and industrial building]. Roczniki Inżynie- the narrow contact area between the renovation plaster rii Budowlanej, 10, 25–30. and the wall. The pores constituting a sort of “venti- Gosztyła, M., Leś, S. & Sikorski, K. (2017). Stary rynek w Rzeszowie – tynki stosowane w procesie renowacji lation system” will be narrowed and the hydrophobic obiektów zabytkowych. Aspekty technologiczne [Old nature of the pores will limit the transport of liquid Market in Rzeszow – plasters used during restoration water towards the outer surface of the plaster (tene- works of historical buildings. Technological aspects]. ment house at Waryńskiego Street). On the other hand, Czasopismo Inżynierii Lądowej, Środowiska i Architek- at low and medium moisture levels, coming mainly tury – Journal of Civil Engineering, Environment and from rainwater, the use of just the renovation plaster is Architecture, 64 (4/I), 89–103. https://doi.org/10.7862/ a good solution. The walls of the building will be pro- rb.2017.195 tected against moisture penetration, especially if they Hall, C. & Hoff, W. D. (2007). Rising damp: capillary only need to be applied to a part of the walls. The reno- rise dynamics in walls. Proceedings of the Royal So- vation carried out in this way will protect the building ciety A: Mathematical, Physical and Engineering Sci- ences, 463 (2084), 1871–1884. https://doi.org/10.1098/ against the harmful effects of external factors and will rspa.2007.1855 increase its aesthetic value and comfort of use. It will Hughes, J. J., Groot, C., Van Balen, K., Bicer-Simsir, B., also preserve historically significant elements of the Binda, L., Elsen, J., Hees, R. P. J. van, Konow, T. von, wall, such as decorative details. Lindqvist, J. E., Maurenbrecher, P., Papayianni, I., Subercaseaux, M., Tedeschi, C., Toumbakari, E-E., REFERENCES Thompson, M., Valek, J. & Do Rosário Veiga, M. (2012). RILEM TC 203-RHM Repair mortars for his- Bajno, D. & Budnik, N. (2019). Wybrane problemy oceny toric masonry: The role of mortar in masonry: an intro- stanu technicznego budynków i budowli w aspekcie duction to requirements for the design of repair mortars. późniejszej naprawy i wzmocnienia [Selected problems Materials and Structures, 45 (9), 1287–1294. https://doi. of assessment of the technical condition of buildings and org/10.1617/s11527-012-9916-0 construction in the aspect of later repairs and reinforce- Lubelli, B., Hees, R. P. J. van & Groot, C. J. W. P. (2006). ments]. Materiały Budowlane, 3, 18–19. https://doi. Sodium chloride crystallization in a “salt transport- org/10.15199/33.2019.03.05 ing” restoration plaster. Cement and Concrete Re- Brachaczek, W. (2018a). Kształtowanie właściwości search, 36 (8), 1467–1474. https://doi.org/10.1016/ współczesnych tynków renowacyjnych [Shaping the j.cemconres.2006.03.027 properties of modern renovation plasters]. Kraków: Misiewicz, J. (2016). Adaptacja zabytkowej kamienicy Na- Polska Akademia Nauk. Oddział w Krakowie, Polskie ujacka na Centrum Kultury w Olsztynie [Adaptation of Towarzystwo Ceramiczne. a historical Naujack tenement house – transformation Brachaczek, W. (2018b). Study of the Impact of Microstruc- into the Olsztyn Cultural Centre]. Przegląd Budowlany, ture and Sorption Properties of the Renovation Plasters 87 (6), 19–28. on the Wall Drying Rate. Periodica Polytechnica Civil Pavlíková, M., Pavlík, Z., Keppert, M. & Černý, R. (2011). Engineering, 62 (3), 792–799. https://doi.org/10.3311/ Salt transport and storage parameters of renovation PPci.11822 plasters and their possible effects on restored buildings’ Charola, A. E. (2000). Salts in the deterioration of porous walls. Construction and Building Materials, 25 (3), materials: an overview. Journal of the American Insti- 1205–1212. https://doi.org/10.1016/j.conbuildmat.2010. tute for Conservation, 39 (3), 327–343. https://doi.org/1 09.034 0.1179/019713600806113176 architectura.actapol.net 63 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Petković, J., Huinink, H. P., Pel, L., Kopinga, K. & Hees, 998-1:2016-12). Warszawa: Polski Komitet Normaliza- R. P. J. van (2010). Moisture and salt transport in three- cyjny. -layer plaster/substrate systems. Construction and Build- Polski Komitet Normalizacyjny [PKN] (2019a). Badania ing Materials, 24 (1), 118–127. https://doi.org/10.1016/ betonu. Część 3: Wytrzymałość na ściskanie próbek do j.conbuildmat.2009.08.014 badań (PN-EN 12390-3:2019-07). Warszawa: Polski Polski Komitet Normalizacyjny [PKN] (2002). Cieplno- Komitet Normalizacyjny. -wilgotnościowe właściwości materiałów i wyrobów bu- Polski Komitet Normalizacyjny [PKN] (2019b). Badania dowlanych. Określanie wilgotności przez suszenie w pod- betonu. Część 5: Wytrzymałość na zginanie próbek do wyższonej temperaturze (PN-EN ISO 12570:2002). badań (PN-EN 12390-5:2019-08). Warszawa: Polski Warszawa: Polski Komitet Normalizacyjny. Komitet Normalizacyjny. Polski Komitet Normalizacyjny [PKN] (2003). Metody ba- Wissenschaftlich-Technische Arbeitsgemeinschaft für Bau- dań zapraw do murów. Część 18: Określenie współczyn- werkserhaltung und Denkmalpflege e.V. [WTA] (1999). nika absorpcji wody spowodowanej podciąganiem ka- Beurteilung von Mauerwerk – Mauerwerksdiagnostik pilarnym stwardniałej zaprawy (PN-EN 1015-18:2003). (WTA 4-5-99/D). München: Fraunhofer IRB Verlag. Warszawa: Polski Komitet Normalizacyjny. Wissenschaftlich-Technische Arbeitsgemeinschaft für Bau- Polski Komitet Normalizacyjny [PKN] (2016). Wymaga- werkserhaltung und Denkmalpflege e.V. [WTA] (2005). nia dotyczące zaprawy do murów. Część 1: Zaprawa Sanierputzsysteme (WTA 2-9-04/D). München: Fraun- do tynkowania zewnętrznego i wewnętrznego (PN-EN hofer IRB Verlag. RENOWACJE BUDYNKÓW Z ZAWILGOCONYMI I ZASOLONYMI MURAMI – ANALIZA PRZYPADKÓW STRESZCZENIE W artykule omówiono zagadnienie renowacji budynków z zawilgoconymi i zasolonymi murami. Przedsta- wiono wyniki badań konserwatorskich murów dwóch budynków historycznych pochodzących z początków XX w. Ustalono, że mury budynków są obciążone wilgocią i solami. Używanie do renowacji takich murów tradycyjnych tynków wapienno-cementowych czy cementowych jest rozwiązaniem doraźnym i krótkotrwa- łym ze względu na ich niską dyfuzyjność. Odpowiednim materiałem są tynki renowacyjne, które powinny być dobierane w zależności od właściwości muru. Przedstawiono różne podejścia do renowacji tych dwóch budynków. Tam, gdzie wilgoć spowodowana była podciąganiem kapilarnym, najpierw odtworzono barierę przeciwwilgociową oraz zastosowano system tynków renowacyjnych w układzie obrzutka, tynk podkłado- wy, tynk hydrofobowy, powłoka malarska. W drugim przypadku, ze względu na częściową tylko wymianę tynków, po zabezpieczeniu elewacji przed wodami opadowymi tynki uzupełnione zostaną obrzutką renowa- cyjną i hydrofobowym tynkiem renowacyjnym. Przed nałożeniem powłoki malarskiej całość powierzchni pokryta zostanie renowacyjną szpachlą wapienną. Słowa kluczowe: tynki renowacyjne, sole w murach, wilgoć w murach 64 architectura.actapol.net http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Acta Scientiarum Polonorum Architectura de Gruyter

Renovation of Buildings Having Damp and Salted Walls – Case Analyses

Acta Scientiarum Polonorum Architectura , Volume 20 (2): 14 – Jun 1, 2021

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Abstract

Acta Sci. Pol. Architectura 20 (2) 2021, 51–64 content.sciendo.com/aspa ISSN 1644-0633 eISSN 2544-1760 DOI: 10.22630/ASPA.2021.20.2.14 ORIGINAL P APER Received: 18.12.2020 Accepted: 24.03.2021 RENOVATION OF BUILDINGS HAVING DAMP AND SALTED WALLS – CASE ANALYSES Wacław Brachaczek Faculty of Materials, Civil and Environmental Engineering, University of Bielsko-Biala, Bielsko-Biała, Poland ABSTRACT This article discusses the issue of renovation of buildings having damp and salted walls. The results of conservation research on the walls of two historical buildings from the beginning of the 20th century are presented. It was determined that the walls of the buildings are burdened with moisture and salts. The use of traditional cement and limestone plaster for renovation of such walls, due to their low diffusivity, is a tempo- rary and short-term solution. A suitable material is a renovation plaster, which should be selected depending on the properties of the wall. Various approaches to the renovation of these two buildings were presented. Where moisture was caused by capillary rise, the moisture barrier was first restored and a system of renova- tion plasters consisting of rough coat, undercoat plaster, hydrophobic plaster and paint coating was used. In the second case, due to only a partial replacement of the plasters, after protection of the facade against rainwa- ter, the plasters will be supplemented with renovation rough coat and hydrophobic renovation plaster. Before applying the paint coating, the entire surface will be covered with a renovating lime putty. Key words: renovation plasters, salts in walls, moisture in walls the walls will dry out. Walls with considerable thick- INTRODUCTION ness which are protected against water may dry out In the renovation of historic buildings having damp for many years under natural conditions. If the drying and salted walls, repetitive treatments leading to a per- procedures are not carried out in an appropriate way, manent reduction in the level of moisture in the walls the damp wall containing salts will continue to be can be distinguished. The procedures are based on the destroyed and degraded. While technologies for con- sequence of operations: source identification → root ducting renovation treatments are known and widely cause removal → repair. Walls are considered dry if used, there is no single universal method which can their mass humidity is at the level of 3–6%. The basic be used for most historic buildings (Charola, 2000). technological renovation activities are related to the The selection of comprehensive technological solu- restoration of horizontal and vertical damp proof in- tions leading to the reduction of the mass humidity sulation, solving the problem with salts, repairing the of walls is still controversial. One method used for walls and refurbishing the facade elements to restore different buildings may sometimes bring different re- aesthetic value (Brachaczek, 2018a). Subsequent op- sults. The reasons for this are manifold. The choice of erations are performed to reduce the dampness of the a technological solution is influenced by many factors walls. Limiting renovation work merely to a restora- ranging from the degree of moisture or salts content tion of moisture barriers only does not guarantee that to the workmanship. The reason may be restrictions Wacław Brachaczek https://orcid.org/0000-0002-4782-8409 wbrachaczek@ath.bielsko.pl © Copyright by Wydawnictwo SGGW Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 related to the condition of the walls or the properties of salt by way of advection or dispersion. It occurs in of the materials which they are made of. Modern re- higher parts of walls with lower humidity, when, as pair materials happen to react with the wall substance, a result of evaporation, the moisture in the outer layer which leads to unexpected effects such as swelling or of the wall is successively enriched with a greater loosening. Further restrictions are related to the very amount of salt ions in relation to the moisture inside method of performing renovation works. Often, the the material. The salt ions will then move towards need to preserve original design solutions does not a lower concentration environment, i.e. opposite to enable performing certain treatments effectively. In the direction of drying (Petković, Huinink, Pel, Ko- particular, these are the situations related to moisture pinga & van Hees, 2010). Under natural conditions, protection of hard-to-reach places that, due to their as a result of alternating damping and drying of walls, unique nature, must be left intact. When drying walls, salts present in the pores undergo cyclic dissolution too rapid removal of moisture may sometimes cause and crystallization. This results in the destruction of damage to the substance of the walls and losing their the wall structure due to the generated crystallization strength due to the capillary forces in the pores. pressure affecting the pore walls of building materials The impact on the nature of the salt-induced dam- (Brachaczek, 2018a). age to the walls depends on the materials and the ex- Regardless of the way the salts enter the walls, they posure of the wall elements. Salts may be accumulated dissolve in contact with water. Due to their concentra- in dry walls for decades and only to a slight degree tion, such solutions may be unsaturated or supersatu- contribute to the damage. The damage is the most se- rated. The supersaturated solution can be found in the vere in damp walls. Salts are crystalline substances, porous structure of building materials if moisture to- easily soluble in water. The most dangerous salts in- gether with the salts dissolved in it continuously pen- clude: sodium, potassium, magnesium and calcium etrates into the walls, and then evaporates in the higher chlorides, nitrates and sulphates. Nitrates occur in the parts of the wall. As the moisture evaporates the salt external environment as products of biological oxida- concentration in the pores increases. This phenome- tion of organic compounds or come from agricultural non is accompanied by an increase in the viscosity of fertilizers. The sources of sulphates in urban areas the solution, and thus a reduction in the rate of mois- are flue gases emitted by the combustion of hard coal ture transport by way of advection. With the gradual and liquid fuels. The occurrence of chlorides can be increase in salt ion concentration, the solubility limit associated with the use of de-icing agents for pave- of the solution is exceeded. As a consequence, ther- ments and roadways. All of these salts can be found in modynamically unstable supersaturated solutions are groundwater (Lubelli, van Hees & Groot, 2006; Hall formed, spontaneously striving to transform into satu- & Hoff, 2007). rated solutions by precipitating excess substance in the The moisture problem applies to most historic form of crystals. As a result of the linear growth of buildings. The most common cause of penetration of crystals from the supersaturated solution, an increase walls by the salt is damage or lack of waterproofing in hydrostatic pressure is observed, which is due to the protection of the walls against moisture from the side increase in the total volume of the crystals and the so- of the ground. In this case, salt transport is the result of lution relative to the volume of supersaturated solution capillary rise of solutions through the micropore sys- before crystallization. The hydrostatic and/or crystal- tem present in building materials (Gorecki & Wyrwał, lization pressures generated in this way may exceed 2010). It can be carried out by means of advection (salt the tensile strength of the material, causing its destruc- transport), dispersion and diffusion (due to salt con- tion. As a result of this mechanism a degradation of centration gradient). As a result of the advection, salts plasters and walls in the moisture zone progresses, salt and moisture are transported towards the outer sur- efflorescence occurs, plasters and paints peel off (Pav- face. The transport by means of advection and disper- líková, Pavlík, Keppert & Černý, 2011). In addition, sion occurs with considerable moisture content. Dif- the dampness of the walls affects the unfavourable fusion is a phenomenon competitive to the transport microclimate of rooms, contributes to the infestation 52 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 of the building by mould fungi or insects, which may pair materials. An example would be mistakes made result in health problems. It also reduces the thermal during reconstruction of horizontal moisture barriers by injection. It happens that injections are performed insulation of the wall. The effectiveness of renovation works on build- improperly in cracked walls containing voids without ings with salted and damp walls depends on proper pre-injection. The pre-injection consists in pre-filling diagnostics and cooperation of specialists qualified holes with sealing mortar, whose task is to fill gaps in specific fields (designers, contractors and technol- and voids in the wall. Another mistake is making injections in stone walls. Holes are often drilled in ogy providers). Partially, the principles of this process are described in the WTA 4-5-99/D instruction titled stones with low absorbency, while moisture as a re- “Evaluation of masonry” (Wissenschaftlich-Tech- sult of capillary rise moves in the joints. In such cases nische Arbeitsgemeinschaft für Bauwerkserhaltung the injection is ineffective because the injected filler und Denkmalpflege e.V. [WTA], 1999). However, cannot penetrate the wall. Another factor affecting the durability of renovation works is the inadequate way due to the complexity of the problem and the devel- opment of new technologies, this instruction can be of conducting plastering works. Occasionally, after a valuable guideline and needs to be combined with restoring moisture barriers, plastering works are car- professional and specialized knowledge. To renovate ried out using traditional lime and cement mortars. In historic buildings, it is necessary to recognize the most cases, such mortars not only limit drying walls due to low diffusion relative to water vapour, but nature and properties of the materials used. After de- tailed testing, materials working well with the original they can also contribute to a serious deterioration of material and thus facilitating the repair are selected. the historic walls due to the mismatching of plasters Determination of the degree of saltiness and damp- to the substrate. Such situations occur in particular ness of walls is only one of the necessary tests (Bajno during renovation. In these cases, the wall is highly varied in terms of strength and has different water ab- & Budnik, 2019). In addition to these, it is also impor- tant to determine other properties, such as the strength sorption. Fresh, thin mortar applied to old walls will of the original materials, sorption coefficient, density, dry quickly. Also the hydration of cement proceeds microstructure of pores, bricks and joints. The devel- quickly, which may result in a significant shrinkage. opment of technologies and materials for the renova- This is when the mismatch between the plaster and the substrate becomes evident. Restricting the free- tion of historic buildings with salted and damp walls was especially pronounced in restoring moisture bar- dom of deformation for these materials generates high riers. The choice of a way of restoration of horizontal tensile stresses in the plaster layer. However, if the insulation depends on the structure of the walls, their plaster yield point is exceeded, it will crack. In broad thickness and, above all, their condition (Brachaczek, outline, it can therefore be pointed out that the shrink- age of plaster layers on the rigid substrate would be 2018b). The buildings have often been rebuilt many times over the centuries, and they have been modern- the direct cause of cracks in a direction normal to the ized and renovated according to the knowledge and substrate. Most traditional plastering mortars are char- technology corresponding to the given era. Cracks acterized by high drying shrinkage and low flexibility and crevices often occur in historical walls, and also which makes them completely useless in renovation works, and their use is even harmful to walls. Special affects the selection of the appropriate method. Due to the thickness of the walls, the chemical injection plaster mixtures modified with plasticizing admix- method is often used to reconstruct moisture barriers. tures (polymers) are suitable for such substrates. Ad- Despite the fact that the modern building materials mixtures based on natural and artificial polymers are enable carrying out works so as to prevent further de- of particular importance here. The improvement is in struction of the walls, a number of mistakes are made the amount of shrinkage, flexibility and adhesion to during the works. Errors can be made at any stage of the substrate and aggregates, water retention, etc. The renovation, resulting in negative opinions about the addition of polymer modifiers to cement mixes im- innovative technological solution or innovative re- proves flexibility of the plasters. As a result, their sus- architectura.actapol.net 53 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 ceptibility to shrinkage cracks is reduced. The most buildings come from the beginning of the 20th cen- suitable material for carrying out plastering works on tury. They were built on a site where originally one- -storey buildings, probably from the turn of the 18th salted and damp walls are renovation plasters. Renovation plasters are intended for damp and salt- and 19th centuries, were located. In both cases, reno- ed walls. These are porous plasters characterized by vation plasters were used for restoration. However, high resistance to salt. Most manufacturers do not offer due to the varying salt and moisture contents in these only a single product but several mortars constituting buildings, different approaches to renovation were presented. a renovation plaster system. Such a system includes: renovation rough coat, renovation undercoat plas- ter, hydrophobic renovation plaster, renovation putty MATERIAL AND METHODS and paint coating. The properties required for such plasters are included in the PN-EN 998-1:2016-12 Study objects The first building – called the Under the Frogs – is standard titled “Specification for mortars for masonry. Part 1: Plastering mortar” (Polski Komitet Normaliza- a tenement house at 12 Wojska Polskiego Square in cyjny [PKN], 2016). In the standard, only the proper- Bielsko-Biała. The tenement house was built in the Art ties of hydrophobic renovation plaster for damp and Nouveau style, and, in addition to the apartments, once salted walls are specified. The issue of renovation housed a well-known winery of Rudolf Nahowski. The house has an irregular shape piled up at the corner plasters is more widely addressed in the WTA 2-9- -04/D instruction titled “Renovation mortar systems” into a high tower. The top floors are decorated with (WTA, 2004). This document does not refer to a sin- imitation of half-timbered wall made of plaster. The gle product, but to a renovation plaster system whose half-timbered wall decoration is also visible on the components have the right properties and are com- level of the third floor on the facade from the side of the Wojska Polskiego Square. At the top of the roof, patible with each other. Although renovation plaster systems have been used for several decades, and in a forged structure with fancifully curled elements, many cases the benefits of using them are obvious, to which winery advertising was attached, was pre- there were also some critical opinions. The reserva- served. Windows with various patterns were arranged tions concerned the adverse impact on wall structure. asymmetrically. The northern wall is decorated with a portal crowned with figurines of two frogs of which In some cases, it has been observed that damp walls covered with renovation plasters tend to retain mois- one holds a mandolin and the other a long pipe in one ture what resulted in the plaster peeling off in winter. hand and a wine glass in the other, resting its elbow on As a consequence, historic building conservators have a barrel, most probably full of wine (Fig. 1). increasingly refrained from using renovation plasters. The second building is located at 2 Waryńskiego Street. It is characterized by a traditional layout of the In some European countries, administrative authori- ties responsible for the protection of cultural heritage block derived from the neoclassical pattern. It consists began to prohibit the use of these materials on historic of a massive rusticated plinth covering the ground buildings. In Poland, the main problems which con- floor. The building has refined flat facades, crowned tractors face are related to the appearance of salt efflo- with a line of strongly shading prominent eaves cor- nice, supported on stone brackets. The walls stand out rescence, the appearance of scratches and cracks, low cohesion, difficulties with application and processing. with their delicate ornamentation of window frames in Although the problems of using renovation plasters the form of wreaths, which makes the whole structure is a topic of constant discussion, it can be concluded seem light. The ground floor with rectangular win- that the reasons for these shortcomings can be seen in dows creates an oblong-shaped plinth with elongated the inadequate matching of renovation technology and rustications. Higher floors with windows framed in materials to the properties of the restored walls. plaster, arranged symmetrically along with the portal This paper presents different approaches to reno- constituting the entrance door frame enhance the im- vation of two buildings from a similar period. Both pression of orderliness and peace. 54 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Fig. 1. The front wall of the “Under the Frogs” house at Wojska Polskiego Square (on the left), tenement house at 2 Waryńskiego Street (on the right) in Bielsko-Biała Under the eaves, there are wreath-shaped decora- colour. In the places where capillary rise occurred, tions. The neoclassical roof with a slight inclination as a result of previous renovation works, the plasters contributes also to lightness of the building, which were replaced with cement and cement-lime plasters. makes it stand out among other tenements. The north- Stucco details were either made of lime mortar or -eastern facade of the building with a wooden floor were plaster casts. They were covered with a layer of balcony and a forged iron railing and brackets closes lime gesso. Inside the building there are stone plinths a string of tenement houses built on the embank- of white marble. ment. Above the roof covered with steel sheet there are huge brick chimneys covered with plaster, while Measurements the walls above the ground are made entirely of full Diagnostic examinations of the walls included visual brick. The building has a partial basement. The floors inspection of the facade as well as determining the level of the non-basement part are made of concrete on of moisture and salt saturation of the walls at the exter- bedding. The basement walls are made of bricks and nal facade and basement walls. Moisture testing of the natural stone and are covered from the inside with masonry was performed using a non-invasive method, cement and lime plaster. The ground floor is vaulted, using Protimeter Surveymaster and Trotec T3000 the upper floors are covered with faceted beam ceil- hygrometers. For this purpose, holes were drilled at ings with sound boarding. Inside the building there heights of 10, 50, 100 and 150 cm from ground level, is a prominent staircase with block steps mounted to a depth of approx. 10 cm. When determining the to the stringers and the staircase wall. The first and vertical lines in which the measurements were read, second floor plasters were made of lime mortar. The equal distances between them were kept. These lines original rustication at the ground floor level and the were routed so as to avoid obstacles. inter-story cornice above the ground floor are made The level of concentration of harmful salts was of strong, dark beige mortar in the dark sandstone determined based on samples of plasters, bricks and architectura.actapol.net 55 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 mortars taken from the central part of the walls on RESULTS AND DISCUSSION each side of the building using a low-speed drill. In Moisture and salt content particular, wall sections degraded to the greatest ex- To determine the degree of moisture, the classifi- tent were examined. The concentration of chlorides, cation for brick walls in accordance with PN-EN ISO sulphates and nitrates was analysed. The tests were 12570:2002 standard (PKN, 2002) was used. The carried out in accordance with the guidelines of the measurement results are presented in Tables 1–3. Ac- WTA 2-9-04/D instruction. The tests on the samples cording to WTA 4-5-99/D in terms of the dampness of were carried out in the laboratory of Sempre Farby the walls, the following division is applied: a wall with company. Table 1. The results of moisture content in walls by weight [%] for the house at 2 Waryńskiego Street Front wall (south-east) Measurement height [cm] 150 14.4 12.6 2.4 2.4 2.6 1.5 11.1 4.3 3.1 100 12 22 11.2 10.9 4.8 4 5 4 3.1 50 10.6 17.2 16.3 9.3 5.5 6 8 14 5.5 0–10 5.5 18.6 13.6 15.9 22 22 16.2 17 3 dry wall wall with increased humidity wall with an average humidity very humid wall wet wall Table 2. The results of moisture content in walls by weight [%] for the house at 2 Waryńskiego Street Sidewall (north-east) Rear wall (north-west) Measurement height [cm] 150 3.4 16.6 10.7 17.8 4.4 18.7 22 100 5.5 4.6 22 9.9 14 5.5 5.8 50 3.8 4.2 9.9 11.3 18.3 3.1 22 0–10 3.6 19.8 13.9 22.0 8.8 19.0 5.7 wall with increased humidity wall with an average humidity very humid wall wet wall Table 3. The results of moisture content in walls by weight [%] for the house at 2 Wojska Polskiego Square from Wojska Polskiego Square from 2 Targowa Street Measurement height [cm] 123123 4 150 1.6 1.7 12.3 1.8 1.6 1.6 5.5 100 3.5 1.7 3.5 1.8 1.8 1.6 1.8 50 2.1 2.5 1.7 8.9 1.9 1.6 1.7 dry wall wall with increased humidity wall with an average humidity very humid wall 56 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 an acceptable mass humidity not exceeding 3%, a wall the wall, as well as the effects of defrosting agents. with increased humidity with humidity of 3–5%, a Building facades from the side of Targowa Street wall with an average humidity of 5–8%, very humid were renovated in the 1990s. The facade from the side 8–12% and wet with mass moisture above 12%. of Wojska Polskiego Square was renovated several The measurement results of the salt content are times, as it was determined based on the stratigraphic presented in Tables 4–5. To determine the degree of studies. the salt content, the classification for brick walls in The building’s facades are in very poor condition, accordance with the WTA 2-9-04/D instruction was both in terms of technology and aesthetics (Fig. 3). used. According to this classification the following Roof eaves, cornices under and over the windows are division is used in respect of the salinity of the walls: secured with flashings or plain tiles. Flashings are a wall with a low salt content, a wall with a moderate damaged, cracked, deformed, and do not fulfil their salt, and a wall with the high salt content. protective function. Lack of protection against water Based on the testing and examinations carried out, caused the mortar to be washed out, loosening strong it can be concluded that the facades of both buildings compact parts of stucco elements. There are numerous are in very poor condition. In the case of the “Under defects on the surface of the cornices, moreover there the Frogs” tenement house, the plinth of the build- are surface peels, stains, salting, cracks, biological ing made of stone is badly damaged (Fig. 2). A direct corrosion. Penetrating and freezing water caused deep cause of plinth damage was splashing rainwater from cracks and peeling off from the surface, individual the street, snow and ice accumulating in this part of loose elements fell off. Table 4. Averaged salt content of the walls of the tenement house at 2 Waryńskiego Street Measurement of salt content and limit values for individual loads by weight [%] loading with salts – limit values Ion type north-western north-eastern south-eastern acc. to the WTA 2-9-04/D wall wall wall low moderate high Chlorides (Cl ) 0 0 0.5 < 0.2 0.2–0.5 > 0.5 2– Sulphates (SO ) 0.2 0.8 0.8 < 0.5 0.5–1.5 > 1.5 Nitrates (NO ) 0.025 0.125 0.125 < 0.1 0.1–0.3 > 0.3 wall with a low salt content wall with a moderate salt content wall with the high salt content Table 5. Averaged salt content of the walls of the tenement house at Wojska Polskiego Square Measurement of salt content and limit values for individual loads by weight [%] salts content – limit values the wall from the wall from Ion type acc. to the WTA 2-9-04/D the Wojska the Targowa Polskiego Square Street low moderate high Chlorides (Cl ) 0 0 < 0.2 0.2–0.5 > 0.5 2– Sulphates (SO ) 0.6 0.4 < 0.5 0.5–1.5 >1.5 Nitrates (NO ) 0.025 0.25 < 0.1 0.1–0.3 > 0.3 wall with a low salt content wall with a moderate salt content wall with the high salt content architectura.actapol.net 57 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Fig. 2. Details of the facade of the “Under the Frog” tenement house at the Wojska Polskiego Square in Bielsko-Biała Fig. 3. Damage to the facade resulting from the impact of rainwater in the “Under the Frogs” tenement house in Bielsko-Biała The destruction of plasters is so great that whole Analysing the results of humidity tests presented fragments of the stucco peeled and fell off. Some stuc- in Table 3, it can be concluded that the moisture level co elements made of thickly applied mortar are con- of the walls building is very uneven. No decrease in nected to the wall with nails and there is a risk that the mass humidity correlated with the height of the they could fall off. Damage caused by water and snow wall was observed. Therefore, it can be assumed that on cornices and the lack of a hydrophobic coating on capillary rise from the foundations side in the walls the surface of the walls caused water to be absorbed is insignificant. With so little moisture, there is no into the plaster and brickwork joints. On the surface need to restore the horizontal moisture barrier. How- of the plasters, stains, moisture, water-soluble salts in ever, the destructive effects of water can be observed the form of efflorescence are visible above the treat- on the building’s facade. The humidity level is high ments, plasters are disintegrated, cracked, detached, in some places. It can therefore be expected that in sanded, with especially severe changes in the lower certain places, as a result of flooding the facade with parts of window bands. Original lime plasters are rainwater, the water content in the walls can be high. heavily weathered and form a crust. In many places When testing the walls for moisture content from the they have become detached from the wall. The main inside, the humidity of the walls did not exceed 3% factors causing damage were: rainwater flowing down by weight. the facade with no flashings, water coming from capil- Analysing the research results of the degree of lary rise and atmospheric pollution. the salt content in the walls presented in Table 5, the 58 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 presence of nitrate and sulphates ions corresponding the front wall directly adjacent to the street. It was also at low to medium content were found. However, no here that the concentration of chloride and sulphates chlorides were found in the walls. Despite the fact was the highest. that the building’s walls are in the immediate vicin- ity of the paved streets, the walls were not loaded Technology and materials used in renovation with chlorides. It should be noted that the plinth of works the building was covered with natural stone cladding In the case of the “Under the Frogs” tenement house, which could protect the walls against the effects of the first scope of renovation works involved inhibiting salts used for de-icing. Based on the examination, it the destructive factors. To this end, in the first stage can be concluded that the stone cladding suffered the of work it is necessary to cut off the supply of water, most due to the influence of external factors, how- both pulled up by capillary rise and flooding facades ever, proved to be an effective protection for this part due to damaged and missing treatments. Fitting the of the walls. missing tiles and reinstalling them in places where In case of the building at 2 Waryńskiego Street, hu- they protected cornices. In the next stage, removal of midity tests presented in Tables 1 and 2 indicated that all secondary elements such as cables, advertisements, the mass humidity distribution in the walls was high. antennas being the source of local moisture penetra- A clear trend of the humidity level decrease along with tion into the walls. The stone pedestal was cleaned of the height of the measurement can be observed on all efflorescence and cement wash – manually or mechan- walls. This indicates the capillary rise of moisture in ically using chisels, hammers and scrapers. All joints the wall and is the result of damaged horizontal insu- were also removed. The stone defects were filled with lation of the building walls or lack thereof. Moisture sealing compound, the joints were filled with grout- is pulled up from the ground by old bricks and mortar ing mortar containing trass. The whole structure was within a capillary system. In addition, an increase in protected with a water-repellent Sempre Aqua protekt humidity in the lower, unsecured vertical insulation preparation based on silicone microemulsion. To re- zone (up to approx. 50 cm above ground level) may construct the stucco details, the Renowator 740 com- come from splashing rainwater. Also, the greatest posite stucco mortar (Sempre) was used. damage in this building was observed in the bottom Since the tenement house is a peculiar piece of ar- part of the plinth and in all places where the flashings chitecture of exceptional historic value, the next stage were significantly damaged and ceased to fulfil their of the renovation will consist in emergency preserva- function (Fig. 4). tion of the facade. The removal of wet, loosened and Analysing the results of salt content in the walls detached plasters has been foreseen. It is planned to presented in Table 4, the presence of chloride, sulphate remove simple plasters in 50%, stucco details in over and nitride ions corresponding to medium content were 30%. The plaster whose condition does not allow found. The highest nitrate concentration was found in structural strengthening and gluing will be removed. Fig. 4. House at 2 Waryńskiego Street, the figure shows the destruction of the walls caused by ground water rise architectura.actapol.net 59 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Well-preserved primary plasters and stucco elements tion combined with pre-injection to restore horizon- will be reinforced with a reinforcing preparation based tal insulation. The pre-injection consists in pre-filling on silicone resins, silicates or fine-molecule silicates holes with sealing mortar, whose task is to fill gaps (tetraethyl silicates), e.g. Renowator 350 by Sem- and voids in the wall. Optionally, in the case of stone pre Farby. As no capillary rise of groundwater from and brick walls with a diverse structure, good effects the foundations was found, the restoration of the hori- are obtained by using gravity injection with an agent zontal moisture barrier was not performed. However, of high consistence. This product contains polysilicate due to the partial moisture penetration in the walls, compounds, well penetrating building materials. They it was decided to replace the removed plasters with form a tight moisture barrier as a result of a change Renowator 545 – hydrophobic renovation plaster for in surface tension of the pores. The advantage of this diffusion plaster rendering. Application of the plaster product is high consistence which facilitates applica- will be preceded by proper preparation of the substrate, tion in walls of high heterogeneity. In order to elimi- consisting in cleaning the wall of dust, dirt and grease. nate the impact of splashing rainwater on the humidity In order to avoid cracks and discoloration on the sur- of the walls, it was recommended to secure the plinth face of the plaster coat, the brittle and weathered joints zone of the walls (at a height of up to 50 cm) with ver- between the bricks will be removed to a depth of 2 cm. tical sealing mortar. Places covered with mosses and algae will be cleaned Due to the considerable destruction of plasters, it with steel brushes and then disinfected with Aglesil was necessary to remove them down to the brick layer. algae remover. In order to reduce the water absorp- Most of the walls were in good condition, however tion before application of the rough coat, the surface they were very wet and salted. The condition of the will be wetted with water. The first plastering layer bricks was very diverse, with some of them strong, will be made of the Renowator 500 renovation coat, and others weak and brittle. The mortar which the which will improve the adhesion of the next layer of joints were made of was largely rotten and brittle. At renovation plaster to the substrate. Unification of the some windows, especially in the upper floors of the facade surface, especially in the places where primary southern facade, cracks of cornices and bands around plasters and renovation plasters are combined, will be the windows could be observed. Due to the high salti- made using Renowator 680 renovation lime coat. The ness and dampness of the walls, higher than in the protective layer will be silicone paint with reduced dirt case of the “Under the Frogs” tenement house, the use adhesion and self-cleaning capabilities (e.g. Sempre of traditional cement and lime or cement plasters for Azzuro). renovation would be a temporary solution. Due to the In the case of the building at 2 Waryńskiego Street, low diffusivity of water vapour, on damp and salted the first scope of renovation work included roof repair walls, such mortars tend to peel away and crack. This phenomenon may be affected by such factors as stress combined with the replacement of roof slopes with window joinery renovation, replacement of flashings caused by salt crystallization, as well as mismatch- together with rainwater drainage system. In order to ing of plaster properties to the substrate. According protect the building against the harmful effects of wa- to Brachaczek (2018b), a single type of renovation ter coming from the ground, it is planned to restore plaster with universal properties should not be used to renovate historic buildings. There is probably no the horizontal moisture barrier by injection. Due to the specific nature of this method, a waterproofing such plaster available anyway. The walls differ in wa- horizontal insulation just above the ground level was ter sorption coefficient, strength, diffusion resistance, planned for all analysed walls, except for possible etc. Whenever choosing plasters, their compatibility pressurized water impact. This will protect the build- with the substrate needs to be checked. Damp walls with a low water sorption coefficient should not be ing parts above the ground against moisture migrating from the ground. The varied nature of the foundations, covered directly with hydrophobic plasters. The low mostly made of stone, and the voids or gaps occur- sorption coefficient of the walls means that the walls ring in it, determined the use of low-pressure injec- dry slowly and the water is stored in them for several 60 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 years. In such cases, only renovation plasters with undercoat plaster, prevents salt from getting outside high water sorption properties may be used for renova- the plaster coat. The thickness of this layer should be tion. In order to avoid the appearance of scratches and 1–2 cm. In order to obtain a smooth, aesthetic surface, cracks resulting from mismatching the plaster strength the facade was covered with a fine-grained vapour- to the substrate, additional compressive and bending -permeable finishing layer of Renowator 580. strength tests as well as sorption tests were carried The proper function of renovation plasters is pos- out in accordance with PN-EN 1015-18:2003, PN-EN sible due to the creation of a suction force causing the 12390-3:2019-07 and PN-EN 12390-5:2019-08 stand- moisture to transfer from the wall to the plaster placed ards (PKN, 2003, 2019a, 2019b). Six brick samples on the wall. This is possible when the plaster water were taken from each side of the building. The aver- sorption coefficient is greater than the one of the brick. aged results are summarized in Table 6. In this case, for the analysed wall materials, the suitable plaster is Renovator 520 undercoat renovation plaster. The sorption coefficient of this plaster is high and it is Table 6. Physical properties of the tested brick greater than the determined wall sorption coefficient –2 –0.5 of 0.3 kg·m ·min . Strengths of renovation rough Tested brick property Value coat, porous and hydrophobic plaster are 4.4, 3.8 and –2 –0.5 3.4 MPa, respectively. They correspond to CSII class Absorption coefficient [kg·m ·min ] 0.26 plasters with a strength of 1–5 MPa. Compared to the Compressive strength [MPa] 5.80 bricks encountered in the building, these plasters have Tensile strength [MPa] 1.79 the lowest strength and should not have a destructive effect on the structure of the walls. This is very im- portant, because in the case of plaster with strength According to the WTA 2-9-04/D instruction, the clearly higher than the material to which it is applied, effectiveness of plasters in wall drying depends on ap- there is a risk of shrinkage leading to the destruction propriate porosity (> 60%) and distribution of pores of the top layer of the brick. Moreover, renovation (the number of capillary and air pores), enabling the plasters containing polymer modifiers have been used capillary transport of moisture, diffusivity (m < 10), for renovation, reducing shrinkage during drying, im- –2 –0.5 surface absorption coefficient w > 1 kg·m ·h . proving plaster elasticity, adhesion to the substrate and The plastering was preceded by preparatory works water retention. consisting in removing fragile and weathered joints to Damaged stucco elements were restored using a depth of 2 cm and supplementing them with fine- Renowator 740 stucco mortar. It is characterized by -grain Renowator 520 renovation undercoat plaster. excellent workability, low shrinkage when drying and The building walls were covered with a system of resistance to weather conditions. In order to insulate renovation plasters with layer thicknesses determined the vertical plinth zone of the building, the lower part on the basis of the WTA 2-9-04 instruction. The wall of the building (up to 50 cm above the ground) was bonding layer was made using a renovation rough cleaned of old plastering down to the brick layer, and coat, which should cover the wall in an openwork pat- then covered with Renowator 300 – two-component, tern, i.e. on 50% of the wall surface, and its thickness highly elastic sealing compound. It protects the cov- should not exceed 0.5 mm. The next layer was made of ered wall against both moisture and rainwater as well Renowator 520 undercoating plaster. The main func- as water penetration. tion of this layer is to store salt. It is characterized by high porosity, high vapour permeability and high water Evaluation of renovation works sorption coefficient. The thickness of this layer should There is a great deal of evidence acknowledging the be between 1–2 cm. Directly on it, Renowator 540 hy- effectiveness of renovation plasters used for renovat- drophobic, vapour-permeable renovation plaster was ing damp walls. The justification of the proposed so- applied. It accumulates salts to a lesser extent than the lutions are multiannual observations of the renovated architectura.actapol.net 61 Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Fig. 5. House at Wojska Polskiego Square (on the left), tenement house at 2 Waryńskiego Street (on the right) in Bielsko- -Biała after renovation buildings and the analysis of the cases described in the may be many times higher (Misiewicz, 2016). Another literature (Dudás & Terjék, 2015; Misiewicz, 2016). mistake is too much filling and smoothing, which con- Figure 5 shows the state of elevation at Waryńskiego siderably lowers the permeability of water vapour. Is Street three years after renovation and the elevation of also unacceptable to fill the corroded plaster by using the building called Under the Frogs after a year. materials of different characteristics than the existing In case of the tenement house at Waryńskiego plaster. It is not allowed to apply materials of low per- Street, the dampness of lower than 3% was obtained meability of water vapour, for instance cement finish after three years from renovation. The appointed time (Hughes et al., 2012). is consistent with the results achieved by (Gosztyła, Leś & Sikorski, 2017) in case of the tenement house SUMMARY AND CONCLUSIONS at the main square in Rzeszów, where renovation plas- ters were also applied for renovating damp walls. The Historic buildings are extremely valuable testimony to qualities of the plasters are frequently overestimated. our culture and their renovation should be approached One cannot expect renovation plasters to be effective very individually. Before starting work, as much in- if the source of dampness has not been removed. In formation as possible about the building needs to be such cases the plasters lose their properties as a re- gathered. Successful renovation must be preceded by sult of storing more salt caused by capillary suction, a series of tests to determine the degree and source of which considerably shorter their durability (Dudás & moisture and saltiness. It is also important to examine Terjék, 2015). It is bad practice of some contactors to additional properties of the wall (such as sorption or apply renovation plasters in the dampest spots, as well strength). Only on the basis of these properties reno- as to combine them with lime-cement of low perme- vation plasters can be selected so as to prevent water ability of water vapour. In this case the wall still re- retention in the walls and the destruction of the sub- mains damp and the dampness in the lime-cement area stance which they are made of. The material solutions 62 architectura.actapol.net Brachaczek, W. (2021). Renovation of buildings having damp and salted walls – case analyses. Acta Sci. Pol. Architectura, 20 (2), 51–64. doi: 10.22630/ASPA.2021.20.2.14 Dudás, A. & Terjék, A. (2015). Efficiency assessment of proposed in the study are optimal for the analysed posterior waterproofing systems of renovated porous wall. In each case, however, the same materials were limestone masonry work. Tehnički vjesnik – Technical used according to a different technology. Application gazette, 22 (5), 1225–1236. https://doi.org/10.17559/ of hydrophobic renovation plaster without the prim- TV-20140715083036 ing layer of salt-accumulating plaster to a wall with Gorecki, P. & Wyrwał, J. (2010). Proces niszczenia murów significant humidity and high load, may hinder dry- ceglanych w zabytkowych budynkach i obiektach prze- ing the wall. In this case, when the water dries and mysłowych [Degradation process of old brick walls in evaporates, the salts will crystallize and accumulate in monumental and industrial building]. Roczniki Inżynie- the narrow contact area between the renovation plaster rii Budowlanej, 10, 25–30. and the wall. The pores constituting a sort of “venti- Gosztyła, M., Leś, S. & Sikorski, K. (2017). Stary rynek w Rzeszowie – tynki stosowane w procesie renowacji lation system” will be narrowed and the hydrophobic obiektów zabytkowych. Aspekty technologiczne [Old nature of the pores will limit the transport of liquid Market in Rzeszow – plasters used during restoration water towards the outer surface of the plaster (tene- works of historical buildings. Technological aspects]. ment house at Waryńskiego Street). On the other hand, Czasopismo Inżynierii Lądowej, Środowiska i Architek- at low and medium moisture levels, coming mainly tury – Journal of Civil Engineering, Environment and from rainwater, the use of just the renovation plaster is Architecture, 64 (4/I), 89–103. https://doi.org/10.7862/ a good solution. The walls of the building will be pro- rb.2017.195 tected against moisture penetration, especially if they Hall, C. & Hoff, W. D. (2007). Rising damp: capillary only need to be applied to a part of the walls. The reno- rise dynamics in walls. Proceedings of the Royal So- vation carried out in this way will protect the building ciety A: Mathematical, Physical and Engineering Sci- ences, 463 (2084), 1871–1884. https://doi.org/10.1098/ against the harmful effects of external factors and will rspa.2007.1855 increase its aesthetic value and comfort of use. It will Hughes, J. J., Groot, C., Van Balen, K., Bicer-Simsir, B., also preserve historically significant elements of the Binda, L., Elsen, J., Hees, R. P. J. van, Konow, T. von, wall, such as decorative details. Lindqvist, J. E., Maurenbrecher, P., Papayianni, I., Subercaseaux, M., Tedeschi, C., Toumbakari, E-E., REFERENCES Thompson, M., Valek, J. & Do Rosário Veiga, M. (2012). RILEM TC 203-RHM Repair mortars for his- Bajno, D. & Budnik, N. (2019). Wybrane problemy oceny toric masonry: The role of mortar in masonry: an intro- stanu technicznego budynków i budowli w aspekcie duction to requirements for the design of repair mortars. późniejszej naprawy i wzmocnienia [Selected problems Materials and Structures, 45 (9), 1287–1294. https://doi. of assessment of the technical condition of buildings and org/10.1617/s11527-012-9916-0 construction in the aspect of later repairs and reinforce- Lubelli, B., Hees, R. P. J. van & Groot, C. J. W. P. (2006). ments]. Materiały Budowlane, 3, 18–19. https://doi. Sodium chloride crystallization in a “salt transport- org/10.15199/33.2019.03.05 ing” restoration plaster. Cement and Concrete Re- Brachaczek, W. (2018a). Kształtowanie właściwości search, 36 (8), 1467–1474. https://doi.org/10.1016/ współczesnych tynków renowacyjnych [Shaping the j.cemconres.2006.03.027 properties of modern renovation plasters]. Kraków: Misiewicz, J. (2016). Adaptacja zabytkowej kamienicy Na- Polska Akademia Nauk. 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RENOWACJE BUDYNKÓW Z ZAWILGOCONYMI I ZASOLONYMI MURAMI – ANALIZA PRZYPADKÓW STRESZCZENIE W artykule omówiono zagadnienie renowacji budynków z zawilgoconymi i zasolonymi murami. Przedsta- wiono wyniki badań konserwatorskich murów dwóch budynków historycznych pochodzących z początków XX w. Ustalono, że mury budynków są obciążone wilgocią i solami. Używanie do renowacji takich murów tradycyjnych tynków wapienno-cementowych czy cementowych jest rozwiązaniem doraźnym i krótkotrwa- łym ze względu na ich niską dyfuzyjność. Odpowiednim materiałem są tynki renowacyjne, które powinny być dobierane w zależności od właściwości muru. Przedstawiono różne podejścia do renowacji tych dwóch budynków. Tam, gdzie wilgoć spowodowana była podciąganiem kapilarnym, najpierw odtworzono barierę przeciwwilgociową oraz zastosowano system tynków renowacyjnych w układzie obrzutka, tynk podkłado- wy, tynk hydrofobowy, powłoka malarska. W drugim przypadku, ze względu na częściową tylko wymianę tynków, po zabezpieczeniu elewacji przed wodami opadowymi tynki uzupełnione zostaną obrzutką renowa- cyjną i hydrofobowym tynkiem renowacyjnym. Przed nałożeniem powłoki malarskiej całość powierzchni pokryta zostanie renowacyjną szpachlą wapienną. Słowa kluczowe: tynki renowacyjne, sole w murach, wilgoć w murach 64 architectura.actapol.net

Journal

Acta Scientiarum Polonorum Architecturade Gruyter

Published: Jun 1, 2021

Keywords: renovation plasters; salts in walls; moisture in walls

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