Damp Assessments

Dampness is a problem which affects a very large number of properties, particularly those that were built more than 100 years ago. Some people are prepared to live with some degree of dampness, but not to the extent that it can cause problems with health & safety or the integrity of a building, and the effect on decor is inevitably annoying. But, is the damp due to Rising Damp, or is it due to some other cause? How extensive is Rising Damp?

If a damp problem is to be properly eradicated it is important that the source of the problem is properly identified. Affected areas need to be allowed to dry out thoroughly before remedial work is carried out. If the source or cause of the problem is not treated, or the problem is incorrectly diagnosed, the original problem will continue to develop and unnecessary or incorrect repair work may cause added problems. Treatments suggested for use in modern construction may not be appropriate for traditionally constructed buildings and can mask dampness retained within the structure, only for such dampness to begin to show in future years.

When damp is found, particularly at low levels, the immediate reaction is to call in a Damp Proofing Company with view to ensuring such dampness is removed. Do they test for Chlorides & Nitrates in the defective plaster before a new DPC is installed to confirm that the dampness originates from the ground, or after they are recalled under the Guarantee? If a Damp Course has already been installed, will further damp proofing treatment be any more successful? If Rising Damp is not the cause of the problem, how successful is a new DPC likely to be? Most dampness tends to originate or be caused by matters other than rising damp.

To obtain full independent advice on the CAUSE of the problem, before recommending how to attend the SYMPTOM by calling 01757 249327. The implications of any chemical DPC should be very carefully thought through BEFORE installation to avoid further potential damage to the building integrity.

David Rawlins, Chartered Surveyor and Historic Building Consultant, will carefully diagnose the dampness found with view to providing verbal advice, or a written report on the damp issues. David Rawlins can help:

  • Understand the nature and the extent of dampness problems affecting a dwelling.
  • Attempt to identify the likely CAUSE(S) of the problem
  • Take account of any repairs or replacements the property needs, by reference to the integrity & age of the building, and how it was built, before advising how to attend the SYMPTOMS of the dampness found in the most appropriate way.
  • Indicate the possible cost of these repairs.

Such assessments are crucial in Listed Buildings, due to the potential for criminal damage, should damp proofing works be undertaken without Listed Building Consent. During the assessment no damaging investigations are undertaken.

Do not to forget the inherent nature of the materials used in old buildings, and how such buildings were constructed compared to modern construction detail. A building of modern cavity construction is specifically designed to stop moisture extending through to the internal surfaces. An old building of solid construction is constructed of porous materials that were not designed to prevent moisture into the building, but equally moisture within the structure was able to evaporate out. ANY impermeable membrane incorporated into or on such a structure will tend to displace such moisture or prevent such moisture evaporation.

Traditionally, walls were constructed using lime mortars and lime plasters, which absorb moisture before slowly releasing it. Modern methods of repair now use cement, which does not have the moisture permeability of lime. A consequence is that moisture is either displaced or held within the structure. Basically, due to rainfall etc it is not possible to prevent moisture entering a wall, but modern methods including chemical DPC`s, use of cement etc, can prevent moisture in the wall from "escaping". The requirements for climate change and the need for thermal efficiency will increasingly be a major cause of internal dampness and condensation in years to come leading to more unnecessary chemical damp courses!

Mortgage Valuers, more often than not due to the requirements of lenders insisting on the use of standard clauses, request a Specialist Report from Companies who may have a profit motive for what they advise and are not members of the Property Care Association. How many contractors, for example, recommend remedial treatment for rising damp, but also recommend the adjustment of outside ground and the repair of that leaking gutter? How many such contractors are recalled by a house owner only for such an analysis of the salts present to be told by the damp company that the damp is not due to rising damp and therefore not covered by their guarantee?

I am also increasingly finding evidence of dampness, including condensation and cold bridging, in old houses where the walls and other parts have been insulated under the "Green Deal" without due consideration given to the format of the construction and without first attending other inherent defects.  I saw a set of 3 cottages recently, where the walls had been cement rendered externally and insulated internally with plasterboard over kingspan 3 years ago. The rapid increase in condensation levels and damp patches due to "cold bridging" where easy to see, and the issue of damp penetration via the chimneys to two of the cottages more difficult & expensive to resolve.

The Standard Pre-Purchase Inspection

The surveyor will carry out a visual inspection of the parts of the property normally affected by dampness and usually includes the walls and floors next to the ground and any floors below (for example, a basement or cellar). this will include the main part of the dwelling and any extensions or additions. The inspection is not a building survey and so the surveyor will not inspect the other parts of the property unless asked.

The surveyor will not take up fixed carpets, floor coverings or floor boards unless they are loose, easily lifted and the occupier has given their permission to do so. No furniture will be moved or secured panels removed. The surveyor will examine floor surfaces and under floor spaces so far as there is access to these and appropriate arrangements can be made.

The surveyor may use equipment such as a moisture meter, porch, ladders (where access to a higher level not above 3 m is required) and other tools required to carry out the inspection. Although the moisture meter is non-invasive, it may leave small holes in plaster and timber surfaces and so the surveyor will ask the owner for permission to use. the surveyor will note in their report if they were not able to check any parts of the property they would normally expect to see. If the surveyor is concerned about these parts, the report tells you about any further investigation that is needed.

The Written Report

The surveyor produces a report of their inspection for you to use and, in appropriate circumstances, send to your lender. The surveyor cannot accept any liability if it is used by anyone else. If you decide not to act on the advice in the report, you do this at your risk.

The report focuses on the dampness problem that you have asked the surveyor to inspect. It describes what was seen and discovered, and, within the limitations of the inspection, it describes the likely extent of the repair and /or replacement work needed to resolve the problem. This is not a precise specification of the work because not all parts of the property are fully inspected or opened up. a more detailed inspection is available to provide a more accurate picture but this will involve disruptive "opening up" work (for an example, taking up floor boards, knocking out bricks / concrete and so on).

An estimate of the cost of repair and/or replacement work will be included. This is not an accurate quotation because it is based on a restricted visual survey. The costs are based on the BCIS Housing Repair Cost Guide published by the Building Cost Information Service of the Royal Institution of Chartered Surveyors. The costs are intended to indicate the financial magnitude of the defects; they are not intended as procurement advice. Before undertaking any building work specific quotations should be obtained from local reputable contractors.

For further information, please see the current RICS Guidance on Damp. Of course, one of the causes of excessive dampness inside a building is Condensation. Again, the RICS have produced a Guidance Note in this regard.  A further useful website that outlines the various issues is at http://www.taliesin-conservation.com/Knowledge_Bank/Archive.html 

NOTE: Where site conditions or climatic issues cannot be fully overcome, it may have to be accepted that there will always be moisture movement in the building and consequently it may not be possible to solve the problem completely. The functional requirements of the traditional building structure, and the environmental expectations of modern demands need to be balanced. The aim should be to adopt sympathetic measures which give the property and its occupants a healthy and habitable future. See Case Studies.