An In Situ Investigation of Rising Damp Mitigation in Buildings and the Prospective Use of Active Thermal Protection

1. Introduction

Many buildings gradually deteriorate as a result of aging structures and inappropriate or neglected maintenance, which can lead to their partial or complete destruction. For this reason, it is often necessary to carry out repeated renovation work using various construction technologies and rehabilitation procedures. As in other areas of building restoration, the development of construction technologies and building products has had a significant impact on the restoration of damp structures. Many of these solutions are based on historically proven principles which, in combination with modern materials, procedures and application technologies, enable significantly positive and long-term sustainable results to be achieved. Their effect is not only to stop the process of masonry dampness, but also to limit or completely eliminate the destructive effects of the crystallization of water-soluble salts, which are transported in structures along with moisture.

Currently, many buildings face the problem of unwanted moisture penetration into masonry. There are several causes for this phenomenon, which in practice are often incorrectly simplified to the absence of water insulation. However, it should be emphasized that various forms of moisture protection have been widely used in the past. These included clays backfill, drainage systems to lower the groundwater level, asphalt coatings, and brickwork using sharply fired, low-absorbent bricks. However, these systems have deteriorated over time, lost their functionality, or required regular maintenance that was not provided. For this reason, it can be observed today that a significant proportion of historic and newer buildings are affected by various forms of unwanted moisture. The consequences are not only damage to masonry and surface layers, but also increased heat loss and deterioration of the indoor environment, which can lead to health problems for residents. From this point of view, it is appropriate to use the term remediation, derived from the Latin word sanus (healthy), which captures the complex nature of interventions aimed at restoring the functionality and hygienic safety of buildings.

The presence of water in building structures is one of the most significant and widespread problems affecting older buildings, not only in our climate zone, but also on a global scale[1,2,3,4,5,6].

As an example, approximately half of the renovation work on old buildings in Belgium is related to high humidity and salt contamination of masonry [7]. The origin of moisture can be attributed to several factors, including accidental failures of water and sewage pipes, damage to rain gutters and roof structures, water vapor condensation, diffusion, absorption, material absorbency, and capillary rise. Moisture significantly threatens the preservation and functionality of structures, as it reduces the mechanical properties of masonry, promotes biological degradation, cyclic freezing and thawing of materials, and salt migration with subsequent crystallization. At the same time, it increases the thermal conductivity of structures, resulting in increased energy consumption for heating.

As early as the end of the 19th century, H. R. Kenwood pointed out in his 1892 work [8] the negative impact of a damp indoor environment on the health of residents and its connection to the occurrence of various diseases. However, this fact remained underestimated for a long time. It was not until the adoption of the Construction Products Directive by the European Council in 1989 that the requirement for the absence of excessive moisture in masonry was officially defined as a basic condition for the hygiene and health safety of buildings [9].

Rising damp is one of the most common and technically challenging problems in older masonry buildings. It is characterized by the capillary transport of water from the subsoil into porous building materials above ground level, a phenomenon that was described in the past by Laplace and Jurin and analyzed in detail in current literature [7]. Rising damp occurs mainly in cases where masonry comes into direct contact with damp soil [10] and there is no functional horizontal waterproofing, or the original insulation has lost its effectiveness. The interconnected network of pores in the masonry acts as a capillary system that allows water to be transported against the direction of gravity [11]. It is therefore important to focus on systematic solutions to this problem [12]. The height of rising damp depends on the complex interaction of several factors, such as the size and distribution of pores, the surface tension of water, and the rate of evaporation from the surface of the masonry, and individual visible traces of moisture may vary [13,14,15]. The effects of rising damp are varied and include the formation of damp patches, salt efflorescence, degradation of plaster, peeling paint, and deterioration of joint mortar. These defects pose a serious threat, especially to historic masonry structures, but also to older residential buildings, as evidenced by laboratory research on the effects of moisture on structures [16], or laboratory research on models of brick masonry exposed to capillary rising damp [17,18]. Since it is clear that a humid environment promotes the growth of mould, fungi and other microorganisms that negatively affect indoor air quality and the health of users [19], it is essential to address the problem of rising damp. Despite the seriousness of these problems, the issue of dehumidification methods for older structures is still relatively narrowly addressed in the international context. The number of professional publications focused on evaluating the effectiveness of remediation technologies is significantly lower compared to literature devoted to the mechanisms of moisture formation themselves. This situation contributes to the spread of inaccurate, unverified, or even ineffective solutions in practice that are not supported by systematic research and can be caused by several variables. The lack or complete absence of any technical or technological records about the examined object that would capture its original condition at the start of the research. Older masonry is a heterogeneous composite of stone, brick, and various binders, which makes it impossible to achieve exact repeatability of measurements. This material variability means that the results of remediation methods from one building are difficult to transfer to another object. The creation of a universal methodology therefore requires a large number of samples, which makes the research logistically and methodologically extremely demanding. Another variable is that moisture transport in massive structures is very slow, and the real effect of remediation often only becomes apparent after long time, which complicates data collection. Serious research requires long -term studies that would eliminate seasonal influences and fluctuations.

New modern technologies, technological processes, methods, and materials could be beneficial in addressing the issue at hand. Progressive technologies are increasingly used in construction practice, and in the case of 3D laser scanning and photogrammetry in older buildings, which are geometrically inconsistent, they can provide effective and accurate recording of the existing conditions of the object as a starting point for research work [20,21,22]. Technologies such as microwave sensory technology and resistance multi-electrode tomography allow the distribution of moisture in masonry to be mapped without invasive interventions [23]. Modern construction methods use materials with controlled porosity and modified diffusion properties. During remediation remediation plaster systems are applied to optimize the evaporation capacity of the structure, thereby preparing the structure for the integration of new technical and technological systems [24]. One of these modern systems that can improve a building in the long term is Active Thermal Protection (ATP). Unlike passive insulation, ATP works with dynamic control of the temperature gradient in the structure. Precise diagnostics and digital recording of the actual condition (obtained using modern methods in the absence of documentation) are essential prerequisites for the correct dimensioning of ATP. This system is not only a thermal barrier, but also an active remediation element that stabilizes the moisture condition of the structure in real time.

This paper focuses on building defects caused by rising damp and analyzes selected remediation measures designed to eliminate it. The article includes results obtained from in situ research, which allow for an objective assessment of the effectiveness of the applied technologies. At the same time, the article discusses the possibility of linking remediation measures through the integration of active thermal protection (ATP) elements, which can significantly complement the improvement of the indoor environment. Significant progress has been made in this area in recent years, as documented by several studies, such as the Solinterra system developed on the basis of principles already used in ancient architecture [25], as well as modern systems of pipe-integrated walls for heating and cooling buildings [26,27]. The combination of renovation technologies with energy-active structures thus represents a progressive approach to the sustainable renovation of older buildings, as demonstrated by other research addressing the use and design of green roofs to improve the thermotechnical condition of older renovated buildings [28].

2. General Description of Remediation Technologies with Emphasis on the Technology Under Investigation In Situ Research

There are several technologies available for solving problems with rising damp. Individual technologies are implemented in various ways, either invasively or non-invasively. When selecting these technologies, several factors play a role in helping to achieve the functionality of the technology [29]. When making your selection, it is therefore necessary to analyze and take into account several factors, such as:

• Access to the structure to be remediated,
• Possible structural disruption (excavation, shocks, vibrations, etc.),
• Size of the work area,
• Financial costs,
• Salinity and pH, which may also limit some technologies.

That is why it is important to pay attention to the classification of individual technologies. There are several classifications, and many publications classify technologies differently. In 1977, Sharpe described the classification of remediation technologies in his publication [30] as traditional and non-traditional. He included technologies that provide an additional insulating layer in the first group. Injection and electro-osmotic systems were classified as non-traditional methods.

A second example of a description of division could be a publication based on the EMERISDA project [31], which divides remediation methods into two main categories. This division is illustrated in Figure 1.

This classification is mentioned in several foreign publications, but it has not been possible to determine the basis on which the technologies were divided into these groups.

Another classification of these technologies is according to the publication [32]. The author divides remediation technologies into seven main groups according to their structural-physical and implementation aspects:

• Technologies ensuring ventilation;
• Technologies for creating additional impermeable layers;
• Technologies for creating crystalline screens;
• Technologies using electro-physical principles;
• Technologies for heating structures;
• Supplementary technologies;
• Related technologies.

At the same time, this division (Figure 2) is supported by divisions within Czech professional literature [29], which divides these methods into direct and indirect methods. Direct methods include those belonging to the first six main groups described below. Indirect methods include group no. 7. Related technologies.

Technology Used in the Case Study

As mentioned above, there are a number of remediation technologies, the implementation and use of which vary. This publication will focus exclusively on evaluating the effectiveness of the undercutting technology used in the examined building.

The principle of this technology consists in gradual, step-by-step cutting of masonry in working sections ideally 0.3 to 0.5 meters long. The cut joint is then cleaned for optimal insertion of additional insulation. After cleaning, a waterproofing layer is inserted and the gap is wedged to prevent possible settling. After wedging, the next section is carried out. This procedure is repeated across the entire area, and it is necessary to ensure that the individual waterproofing strips overlap. This overlap should be approximately 5-10 cm. PVC pipes are then installed in the structure, and the surface is sealed with mortar. Once the mortar has hardened, the joint is filled with expansion mortar.

The advantage of this technology is that current technological capabilities have enabled the application of this method to a wide range of masonry, including brick, stone, and mixed masonry, even in structures of varying thicknesses. The effectiveness of this technology has been confirmed by several scientific studies, including previous research by the authors, as well as various international publications. An example is the published research documenting the use of masonry undercutting technology on the Pristina University building [33]. Another example is the study [34], describing the use of undercutting technology on a building in the Serbian city of Zrenjanin. The authors state that the technology used can be considered effective with 100% elimination of rising damp, as the technology ensures that all horizontal walls are cut as low as possible from the floor. The authors justify the use of this technology due to high moisture levels, which required effective and radical intervention. At the same time, they consider this technology to be fast, effective, and economically advantageous. This statement can be followed up with Schmidt's statement, which describes undercutting technology in detail in his publication [35] and characterizes it as an invasive and economically more demanding intervention, but with the significant advantage of rapid onset of action and a high degree of reliability.

Despite these positive characteristics, it is essential to pay attention to the importance of professional implementation, as incorrect application can lead to a reduction or complete loss of the functionality of the remediation measure [36]. For the reasons mentioned above, undercutting technology can be considered a globally widespread method for dealing with rising damp.