Rising damp is the phenomenon of ground moisture passing through the sub-floor and lower walls. This often happens when there is inadequate damp proofing membranes in solid floors or a lack of a damp proof course in the lower walls to separate the sub-floor from the ground. Sadly, rising damp is a difficult problem to solve and it generally requires extensive work to implement a retrospective fix.
Commonly, damp and mould appear in patches on internal walls which can be a result of external moisture such as driving rain, bridging through the cavity to the inner skin masonry or timber layer. This might occur when there’s rubble within the cavity or excessive mortar stuck to cavity wall ties. Failed cavity wall insulation can also be to blame for damp walls, and this has increasingly become a problem where materials such as blown mineral wall have started to break down within the wall, enabling cold spots to form. We’re seeing many cases of damp and sodden mineral wool insulation in cavity walls, and we often recommend it is extracted and the cavity cleared before being reinsulated with a more suitable material.
Another common cause of damp walls is a lack of ventilation within the home. Thanks to better insulation, the fabric of our homes is gradually becoming airtight and less ventilated. The plus side is that better, airtight insulation leads to lower energy costs, but the side effect of reduced natural ventilation can manifest itself in the form of damp, mould, and condensation. When we breathe, shower, boil the kettle, dry our clothes, or cook, we generate interstitial condensation which needs to escape from the home. Traditionally built homes may have had plenty of natural ventilation points but with our homes becoming better insulated, mechanical ventilation is vital in maintaining a healthy living environment.
Check out our ventilation page to find out how our solutions can help offset better insulation!