Home buyer surveyor claims rising damp without evidence

RICS, PCA, HISTORIC ENGLAND JPS REPORT

There has long been disagreement about the causes of damp amongst surveyors. Historic England surveyors represent one extreme. They typically do not believe rising damp is a likely cause of internal dampness and rarely recommend altering walls to alleviate damp. By contrast PCA surveyors typically recommend rising damp treatment whenever they see dampness at the base of a wall and often recommend altering a building. RICS surveyors tend to be somewhere near the centre of these extremes. However, unlike Historic England and PCA surveyors, they rarely specialise in damp and often refer issues to PCA surveyors. We and most other independent surveyors are more closely aligned with Historic England’s position except that we are perhaps more pragmatic. For example, if a hole in the wall is the optimum way of solving internal dampness, then we will recommend it, but not otherwise.

JPS questions and answers

1 A summary of the surveyor’s observations, including an Assessment of Significance.

Damp at base of most internal and external walls, not evenly horizontal across all walls as it would be were rising damp the root cause.

2 The importance of regular building maintenance and how a lack of even basic maintenance can lead to problems arising. This is especially important and relevant to roofs, gutters, hidden gutters, rainwater disposal and changes in external ground levels.

As is common with all buildings, gutters and other rainwater goods should be checked twice annually, ideally during or soon after a rainstorm, for evidence of overflow and rain not being dispersed properly from the property. You should also check that there is no flow of water flow during periods of absence for signs of a leak, for instance, by note the number on the mains water meter outside your house. rainwater waters drains have not been kept free flowing

3 An impartial diagnosis of the damp problem, which should be clearly explained and laid out systematically to communicate the relevant risks to the reader.

sub-floor vapour from blocked rainwater gullies

4 Where recommendations for the repair and recovery of moisture-affected structures are stated, the solutions should be clearly explained and prioritised as appropriate.

The solutions are explained in the Recommendations section. The primary recommendation is unblock rear drain, by pass front drain, increase sub-floor air flow, monitor sub-floor relative humidity, monitor dampness in walls, increase ground floor ventilation and dehumidification, monitor internal relative humidity and dews point making sure to keep the internal dew point below the outside temperature

5 The client should be provided with alternative options for which each recommendation should include advantages and disadvantages and the relevant cost and time implications.

This question is primarily directed at PCA damp proofers, to encourage them to consider methods that address the source of water not just the symptoms, such as by hacking off plaster and replacing it with slurry. You can sometimes take this damp proofing approach with short-term success. However, water will eventually find its way through. Furthermore, treatment is disruptive resulting in high cost and a poor finish, with no worthwhile guarantee of success. It likely to lower the value of the property. In our opinion you are better off trying to stop the water at its source, as we recommend. ”

6 Where monitoring and staged interventions are appropriate or beneficial, the client should be informed of the reasons for these options, together with the likely cost and time implications of such recovery strategies.

Properties should be monitored for humidity and temperature using data loggers, see datalogger section of this report. The cost of data loggers is currently less than £20 for two, aim to keep the dew point, as shown on the app screen of each logger (bottom centre on the SensorBlue), within 3°C of the external temperature, especially at night (use ventilation and/or dehumidification to reduce the internal dew point – measure external conditions or refer to weather forecasts for night-time temperatures, such as BBC Weather – a short explanation is; that this will make sure the relative humidity of all surfaces will be below the mould point even if poorly insulated). We also suggest noting values monthly using a multi-functional radio wave and conductance damp meter costing about £24 to monitor and map damp patches on internal walls. This way you can monitoring the dry progress, which typically takes 1 month per 25mm thickness of walls and more if coated. This helps determine if the root cause has been fixed or there is an additional or new source of water, and therefore more actions are required. Ideally this should be started before or soon after starting our recommendations and for about a year, repeating monthly to check progress.

7 Where appropriate, clearly state whether the building concerned represents a financial risk to the buyer or lender and why.

Dampness at the base of the walls, caused by the high sub-floor relative humidity, is not visible and therefore largely superficial. However, with the rear drain being blocked and the front drain likely cracked, there is a theoretical risk of rot affecting structurally significant joists that support the timber floor. The financial risk is estimated to be in the low thousands. Once the drains are repaired and the sub-floor relative humidity is reduced to 85% RH or below for the majority of the time, the risk will diminish to an insignificant level.

8 Any conflicts of interest should be clearly stated.

There is no conflict of interest. We never profit from our recommendations.

As a background, although we charge a fee for undertaking damp surveys, profit is not our primary motivator. We are motivated to:

• solve damp problems in properties,
• encourage clients to spend money wisely for the protection of the property and, where possible to lower the environmental impact,
• stop or at least play our part to reduce the over-diagnosis of rising damp and so called “damp proofing” treatment by replacing plaster with chemicals and slurry, rather than dealing with the root cause.