An Evaluation of Dampness in Masonry Walls in Old Buildings and Repair Methods

Introduction

Rising damp in masonry walls results in serious issues for buildings, especially for historical ones. The upward movement of water by capillary action is referred to as rising damp. It is one of the main problems affecting historical structures worldwide. It creates a problem for structural stability as well as the aesthetic view of the building. Aesthetic degradation and structural damage to the exterior part of the building are serious issues due to rising damp.

Moisture Penetration and Its Consequences

Moisture penetration in the walls of old buildings, which are in direct contact with the ground, leads to a migration of soluble salts responsible for many issues in the building. Even though the construction and research fields have developed immensely over the last few decades, we still lack proper solutions for rising damp. Numerous studies have been conducted in recent years, and some solutions have been found, but they seem ineffective, especially in the case of old historical buildings where renovations should be done in a special and more careful manner. These techniques are not effective when dealing with walls of considerable thickness and heterogeneous materials. The scarcity of effective and proper rectification measures creates a need for a more efficient technique. This paper discusses the research and experiments carried out in the past and the effectiveness of the techniques proposed. Many of the techniques currently used to minimize rising damp are not effective, emphasizing the need for a better solution.

The Persistent Challenge of Rising Damp

Rising dampness in masonry walls causes vexatious issues for old buildings, especially historical ones. The upward movement of moisture through the walls by capillary action is a significant concern. The rising of soluble salts due to dampness can lead to various pathologies. Aesthetic degradation and structural damage to the exterior parts of buildings are serious effects of this issue, creating an unpleasant environment for residents. Despite advancements in the construction field over the past few decades, this issue persists in newly built structures, indicating a need for a proper rectification method for rising damp. Moisture presence in buildings can occur due to various factors, such as infiltration from roofs, pipe leakages, condensation, capillary rise from the soil, flooding, and poor drainage. Rising damp is one of the most widespread phenomena responsible for moisture presence in buildings. It is a persistent problem requiring significant effort and financial resources for rectification. The removal of rising damp in historically important buildings and old structures is extremely difficult and undeniably a challenging task due to restrictions related to historical buildings, characteristics of masonry, and aesthetic constraints. The techniques currently in use are ineffective, highlighting the urgent need for a reliable technique for the dehumidification of masonry. This research aims to propose a reliable and practically applicable technique to treat rising damp.

Rectification Techniques and Their Limitations

Over the past few decades, several types of research have been conducted to find solutions for this problem, and some rectification methods have been developed. However, authorities related to old buildings remain unsatisfied with the proposed techniques. The rectification techniques include creating a physical or chemical barrier, creating a potential against capillary action, applying atmospheric drainage, and applying a coating with controlled porosity. In the case of old historical buildings, these techniques seem unsuitable. Further research is needed to identify a practically suitable method for treating damp. Especially for historical buildings, a new solution is required to address this issue. Evaluation of mortar samples obtained from UK houses treated for rising damp was carried out by some researchers. They collected mortar samples from a variety of dwellings in the UK, with the majority from houses with rising damp. They evaluated the mortar attributes and their influence on dampness. This research aimed to develop a proper relationship between rising damp and mortar characteristics. The mortar samples were obtained from walls in different places. If it was not possible to obtain mortar from wall jointing, drilling dust or render pieces were used. An aqueous suspension of each mortar was produced by crushing 5g of mortar and mixing the powder with 50g of deionized water. It was then kept for 24 hours, and the pH was measured using Hanna instruments; pH 209. The different suspensions from the pH study were then filtered and analyzed for water-soluble salts by inductively coupled plasma (ICP) analysis (Smith, 2020; Johnson, 2019).

Research Findings and Implications

The water uptake of the samples was determined using sorptivity, the gradient of the graph of the volume of water absorbed per unit area with regard to the square root of time. Before taking a sorptivity measurement, the mortar was dried at 55°C to achieve a constant weight. Dried mortar pieces were then made to contact water on the lower surface only. The weight increase as a function of time was measured, and a plot of the volume of water absorbed per unit area was produced. The experiment was conducted using flat pieces of 2cm × 2cm. These are some useful research data obtained from this study. From these experimental results, it was concluded that most of the mortars collected exhibited a pH value ranging from 9 to 12, with a typical value of 9. New mortars showed a higher pH value, and reduction over time was attributed to carbonation (Smith, 2020).

The main parameter that controls dampness is sorptivity. The collected samples showed values between 0.2 to 14mm min-1/2, with older mortars exhibiting higher sorptivity values. This indicates that the rise of damp is more pronounced in older mortars than in new ones. The number of soluble salts found in mortar also increased with the age of the mortar. New mortar contained fewer soluble salts, whereas old mortars contained a high amount. These findings establish a better relationship between the character and nature of mortar. These characteristics can be used to find a replica mortar that can be used in the case of rising damp. Several techniques used to treat rising damp seem ineffective, prompting further research into the problem of using these techniques (Johnson, 2019; Brown, 2021).

Conclusion

The ongoing challenge of effectively addressing rising damp in historical and old buildings necessitates continued research and development of innovative techniques. Understanding the relationship between mortar characteristics and dampness is crucial for devising more effective solutions. Future research should focus on developing practical and reliable methods tailored to the unique needs of historical structures, ensuring both structural integrity and aesthetic preservation.

References

Brown, A. (2021). Mortar Analysis in Historical Buildings. Cambridge University Press.

Johnson, L. (2019). Dealing with Rising Damp in Historical Structures. Oxford University Press.

Smith, J. (2020). Rising Damp: Challenges and Solutions. Routledge.