An issue that bugs many habitants of a traditionally built home (built before 1919), and an issue that is important to rectify before the retrofit or installation of insulation into the building. The results of its treatment can certainly improve the environment and performance of the property, damp in walls makes it less thermally efficient, so drying out a wall can improve the thermal performance of it by around 30%.
The common signs of damp are:
- A damp and musty smell.
- The appearance of mould, salts or mildew on walls, floors or ceilings.
- Walls, floors or ceilings that feel cold or damp.
- Dark or discoloured patches on walls or plaster.
- Lifting or peeling wallpaper.
- Excessive condensation on windows.
The causes of these symptoms can be due to penetrating damp, caused by changes to the building such as rendering, re-pointing, damp proofing, extensions and installation of services etc. Additional excess moisture either liquid water or water vapour can be created by cooking and showering etc.
Buildings of ‘traditional’ construction (pre 1919) tend to have solid walls, and sometimes solid floors, built using ‘breathable’ materials that allow the free passage of moisture ( SPAB, 2018, p3). These include stone, soft brick, unfired earth, lime-based mortars and plasters, and limewash. They take in more moisture than their modern substitutes but allow it to evaporate readily when conditions become drier. Its important to ensure that appropriate methods to mend traditional buildings are used, simple treatments to modern buildings such as a cement based render on a traditional building can cause significant harm.
Figure 1 Cement render aiding the erosion of the bricks
A bit of time and research should be undertaken before the installation of insulation to solid walls, roof spaces and floors. Any of these modifications could cause harm and increase damp issues if improper methods and materials are used. Treating areas that may have been modified with modern methods should be assessed on whether further remedies should be undertaken. With all buildings, good maintenance and care is essential to help control dampness. Prevention is better than cure. Good preventative maintenance, involving uncomplicated tasks such as clearing gutters and rainwater pipes, will help avoid the need for repairs, prevent the loss of original fabric and also be cost effective. Ensuring areas like bathrooms and kitchens are well ventilated is also a good practice to avoid the build-up of water vapour. Moisture sensors and alarm systems can be installed to warn of excessive moisture conditions in building envelopes, especially in hidden or difficult-to-access areas.
Keep up to date with our latest news and blogs by checking back in on our ‘News & Views’ page on the GreenBuild Consult website. Follow our social media platforms by following the icons below:
Written by Ceris Fussell | Sustainability Consultant
SPAB. 2018. Control of dampness. Available at https://www.spab.org.uk/sites/default/files/Control_of_Dampness_0.pdf [accessed 12/11/2020]