Rising damp in walls occurs when there is no damp proof course (DPC), a defective or damaged damp proof course or when the existing course is physically bridged. Water rises up from the subsoil below, travelling through the natural pores in the building material this will in turn cause renders, plaster and wall coverings to become wet. In the worst case it can lead to structural damage affecting timber floor structures it can even disrupt electrical circuits on walls with sockets and switches.
How will I know if Rising Damp is present?
There may be damp patches on the walls normally below a height of 1.5m, wallcoverings may blister and peel and hygroscopic salts may appear at the surface often seen as a whitening (efflorescence) on exposed masonry. Electrical back boxes can corrode and woodwork may split and crumble. In advanced cases a clearly distinguished ‘tide’ mark will be visible. Skirting boards, joists and other structural timbers can subsequently suffer from dry or wet rot depending on conditions.
What can be done about Rising Damp?
The first and most important task is to obtain a clear and accurate diagnosis, Wessex Damp and Timber will provide a comprehensive damp and timber survey with a written report and if necessary a specification for remedial works.
Rising damp is often incorrectly identified and is easily confused with condensation and penetrating damp. A remedial works may be as simple as lowering an external ground level or removing external render that has been taken all the way to the floor (both can bridge a damp proof course). Internal plaster, hidden behind skirting, might be in contact with a solid floor or screed allowing moisture to travel up the wall also. Internal plumbing leaks and defective rainwater goods (guttering etc.)can all contribute, providing symptoms that are common to rising damp. Poor build quality where mortar droppings in a cavity have bridged the DPC or even debris from window and door replacements can do the same.
If rising damp has been identified and correctly diagnosed then there are a number of treatment options available dependant on the type of construction:
- Physical DPC
- Chemical DPC – Low and High pressure.
- Electro-osmotic system
Commonly replastering is necessary particularly to remove hygroscopic salts which can continue to present damp symptoms long after the insertion of a new DPC. Again dependant on the materials used in construction a specific replastering detail will, if necessary form part of you remedial specification.
If you have any concerns or if a pre purchase building survey has highlighted issues then call us today 0800 161 3078 or complete the contact form and we can provide advice or a free of charge survey.