Damp and Timber Surveys
At Nicholson Price Associates we are experts in providing damp surveys on aged properties. After structural defects, damp and timber decay is probably the most common concern for people considering buying a historic building.
Almost without exception, every traditionally constructed building will have a certain amount of damp. Whether it is causing harm to the building or the occupants is a matter of fact. Whether it is a significant issue is often a matter of opinion decided by the client or in some cases their lender.
Without the benefit of membranes and wall cavities, historic buildings do absorb a certain amount of moisture. In many cases, this has little or no effect on the structure. If the building has inherent design flaws, has been neglected or altered in such a way that the ability of the fabric to release excess moisture has been reduced, then problems can occur.
We assess the type, level and consequences of any damp during pre-purchase surveys using non- invasive techniques. Assessing the level and type of damp requires a good understanding of traditional building construction and also the mechanisms that lead to the development of damp. The variables involved in damp problems are considerable, but by looking at the building holistically and applying deductive reasoning it is normally possible to identify the cause without the need to use destructive methods of surveying.
We do use some equipment when assessing dampness. This includes a Protimeter which will tell us the level of moisture in timber as well as the level of ambient moisture and the risk of surface condensation. We also use a thermal imaging camera, although in most cases the equipment only confirms what we have already discovered by using our natural senses.
For technical or legal reasons it is sometimes necessary to undertake some destructive testing to obtain quantitive results during the damp and timber survey. This type of investigation normally involves the removal of numerous drilled samples of masonry. These are then analysed in a UKAS accredited laboratory to determine the precise amounts of moisture and the type and level of salts that may be present. This provides us with an accurate 3D map showing how the moisture is distributed through the masonry. Due to the invasive nature and cost of this type of testing we normally only become involved in high-value projects or projects where the quality and effectiveness of remedial work needs to be measured.
We have extensive experience diagnosing problems relating to timber decay and infestations by wood-boring insects for residential and commercial clients. As part of our damp & timber surveying, we produce sensitive and pragmatic designs for the repair of historic timber.
There are numerous insects that will damage timber. The two most often encountered in damp & timber surveys in the North West of England and Wales are the Common Furniture Beetle (Anobium Punctatum) and Deathwatch Beetle (Xestobium Rufovillosum).
The Common Furniture Beetle is often found in historic buildings and its control and eradication are normally straightforward. Wood boring insects tend to favour damp or decaying timber. The preferred way to eradicate an infestation is by ensuring the moisture content of the timber is kept below the level where it becomes palatable. This, however, is not always possible. We have discovered active common furniture beetle thriving in early twentieth-century softwood with a moisture content of just 12%. This is much lower than the commonly used threshold of 15 -18%.
Common Furniture Beetle normally confines itself to the sap wood. In historic softwood, the proportion of sapwood to heartwood is relatively low, therefore serious structural damage is rare, but it can happen.
Death Watch Beetle can be very destructive and is common in historic timber frame buildings.
Eradicating this insect is not easy. Reducing the moisture content of the timber must be the priority, but colonies of beetles can exist in relatively dry timber, albeit timber that has previously suffered from decay. Like the Common Furniture Beetle, Death Watch normally attacks the sapwood, not the heartwood, but structural damage does occur usually in areas that are difficult to access and inspect.
Dry Rot (Brown Rot, Serpula Lacrymans)
Unfortunately, the majority of the Dry Rot outbreaks we investigate have been active for some time but gone unnoticed. Until either some structural changes have occurred or the fungus has appeared in the living space. Dry rot can be localised and cause minor damage or widespread and seriously damaging.
The fungus and its effect are distinctive and easily identified by a competent damp & timber surveyor. What can be less easy to identify is the extent of any spread. A visual, non-destructive damp survey can sometimes identify hidden dry rot outbreaks, but we normally undertake a strategic endoscopic investigation. This allows us to see any fungus in locations such as floor voids or behind wall panelling.
Using the same small inspection hole we also measure the ambient moisture content in the voids to see whether this may be a contributing factor in the development of the fungus. If Dry Rot is found during an endoscopic inspection or the environmental conditions appear suitable for its development, then we will recommend opening up of any areas at risk.
Wet Rots (White and Brown Rots, various types)
In the course of a damp & timber survey, we tend to encounter Wet Rot more often than Dry Rot. It can cause serious structural damage but tends to be more localised.
Typically Wet Rots will be found in door frames, window frames, external joinery and the ends of embedded timbers. Basically anywhere where timber is in contact with damp masonry or subject to chronic wetting. The precise identification of the fungus is not usually necessary. What is necessary is to identify the source of the moisture that has led to the decay. In some cases, this is obvious to the untrained eye. In other cases, the source and route of the moisture can be more difficult to establish.
Commissioning a damp & timber survey from us ensures that you will receive impartial well-informed advice based on current best practice and a sound understanding of all of the practical, legal and economic issues.