How Homebuyer Surveys and Mortgage Requirements May Funnel Buyers Towards Damp-Proofing Solutions– And Why Traditional Methods May Be Overlooked

In the home-buying process, any potential for dampness or timber decay can quickly complicate matters. If these issues are flagged in a RICS (Royal Institution of Chartered Surveyors) Homebuyer Survey or Building Survey, mortgage lenders often require further investigation, commonly a ‘timber and damp’ survey. This additional step can inadvertently guide buyers toward PCA (Property Care Association) registered companies, who frequently recommend damp-proofing interventions that may be unsuitable for traditional properties. Here, we’ll explore how this process leads buyers toward specific solutions, the limitations of common damp surveys, and how gravimetric testing offers the most reliable method for diagnosing damp in line with British Standards.

Please note: Some of the UK’s leading damp experts are members of the PCA, many of which I personally hold in high regard. Please take some time to study internet forums and you will witness many first hand accounts of misdiagnosis and unsympathetic remedial works carried out by PCA members. My own personal view is that I would never discount the validity of a company solely due to its PCA membership, however, I would expect the survey and suggested remedial works to be unsympathetic to a heritage building.

The RICS Homebuyer Survey: Identifying Issues That Trigger Further Investigation
A RICS Homebuyer Survey or Building Survey provides an overview of a property’s condition, pinpointing potential issues like damp or timber decay that may affect its value or longevity. If the potential for dampness is found during the survey, mortgage lenders often insist upon a more detailed ‘timber and damp’ survey. This stipulation often directs buyers toward PCA-registered companies to undertake a specialist inspection.

While intended to ensure a thorough investigation, this approach may inadvertently lead buyers towards companies with a vested interest in modern damp-proofing techniques. Many PCA-registered companies lean toward chemical damp-proofing as a go-to solution, despite these methods potentially being inappropriate for older buildings that require breathable, moisture-managing materials and traditional construction techniques. The result is a funnel effect that often leads to recommendations of invasive damp-proofing methods rather than traditional, heritage-conscious solutions.

Why Conventional Timber and Damp Surveys Can Be Misleading
In a typical PCA timber and damp survey, non-invasive tools like electrical moisture meters are frequently used to measure surface moisture levels. Although these methods may seem adequate, British Standards reveal their fundamental limitations for assessing moisture in masonry:

BS 5250 (Code of practice for controlling condensation in buildings) clearly states, “accurate measurements of the moisture content of brick or mortar cannot be obtained by the use of electrical moisture meters because the presence of salts increases the electrical conductance of the water, giving falsely high readings.”

BS 6576 (Code of practice for diagnosing rising damp) further explains that “surface measurements cannot alone give proof of rising damp, so further evidence may, where permitted, be obtained by measurements taken within the depth of the wall.” To achieve this depth, chemical (carbide) or gravimetric methods should be used.

Electrical moisture meters used in most basic surveys are extremely inaccurate and often misrepresent the true state of moisture within the wall. This is especially concerning in older buildings, where moisture is often absorbed over time and distributed through the materials due to capillarity, the use of inappropriate materials or inadequate ventilation. Without deeper analysis, many timber and damp surveys misdiagnose the underlying issues, resulting in recommendations for damp-proofing treatments that may exacerbate rather than resolve the problem.

The Importance of Gravimetric Testing for Accurate Damp Diagnosis
For a reliable assessment of damp, gravimetric testing is the most accurate diagnostic method. Gravimetric testing involves taking a core sample from the wall, drying it, and comparing the dry weight to the wet weight to calculate true moisture content. This method provides a precise reading of damp levels within the material itself, bypassing the inaccuracies associated with salts and other factors that skew electrical readings.

Carbide testing, another invasive option, can also offer a more accurate picture than surface readings, though it’s less precise than gravimetric analysis. Both of these methods align with BS 5250 and BS 6576 as recommended practices for correctly diagnosing damp, particularly in traditional or heritage structures.

Without these methods, many structural waterproofing focused surveys lead buyers to believe that rising damp or excessive moisture is an ongoing issue, often recommending chemical damp-proofing treatments that may not only be unnecessary but potentially damaging to solid-walled, older buildings.

The Shortcomings of Damp-Proofing Solutions for Traditional Buildings
Following a PCA timber and damp survey, the final report often includes recommendations for chemical damp-proofing, such as injecting a damp-proof course (DPC) or tanking walls with waterproof coatings. While these methods are effective in modern, subterranean buildings, they often prove problematic in traditional solid-walled structures. Here, trapping moisture within the wall structure can lead to more severe issues, including spalling of masonry, internal condensation, and deterioration of original materials.

Traditional buildings benefit from breathable materials like lime mortar, which allow moisture to evaporate out of the walls. This approach respects the natural breathability and hygroscopic (moisture-absorbing and -releasing) qualities of the materials and allows moisture to escape rather than become trapped.

Disputing Damp-Related Findings: Obtaining a Heritage-Professional Report
If a mortgage lender insists on a PCA-led damp survey and the results recommend invasive damp-proofing measures, it’s possible to counter the findings. By engaging a heritage professional with expertise in traditional construction, buyers can secure a report that offers an alternative perspective, emphasising the building’s historic context and considering appropriate, less invasive methods.

A heritage professional, following BS 5250 and BS 6576, can conduct in-depth testing to ascertain accurate moisture levels. Their report can be used to negotiate with mortgage lenders, providing a more balanced view of the property’s condition and recommending approaches that align with its historical character. This route can prevent inappropriate and damaging treatments while upholding the building’s integrity.

You can also ask your timber and damp surveyor if they have followed BS 5250 and BS 6576 and if so, can they provide data such as gravimetric or salt analysis?

Navigating the process of RICS surveys and mortgage requirements can be challenging, especially with the common funnel effect toward damp-proofing interventions. While many PCA surveys rely heavily on surface-level testing, gravimetric testing, as supported by British Standards, provides the only truly reliable means of diagnosing damp in masonry. By seeking out a heritage-focused second opinion, buyers can avoid unnecessary damp-proofing and protect the authenticity of traditional properties, ensuring both their investment and the building’s historical value are preserved.

A very important final note: Selecting a surveyor with expertise in heritage properties and a comprehensive understanding of the RICS and PCA Joint Position Statement (view here) is essential! The quality and perspective of the surveyor can indeed make a substantial difference in the recommendations provided. A surveyor deeply familiar with heritage structures can provide a more nuanced and sympathetic report, often reducing the likelihood of unnecessary or invasive investigations. In contrast, surveyors without this level of understanding may rely more heavily on further intrusive investigations, potentially recommending interventions that don’t fully respect the building’s historical integrity or actual needs.

It’s especially true that when dealing with older or listed buildings, a surveyor who genuinely appreciates traditional construction methods can often identify and contextualise issues in a way that aligns with maintaining the building’s character. This approach can prevent the immediate involvement of PCA-trained specialists, which might otherwise lead to treatments that could compromise the building’s original materials and its inherent moisture management systems.