Types of Damp - Rainwater leaks
Rainwater penetration is usually found where there has been damage or poor maintenance. Frequent problems that could cause this are missing or broken tiles or slates, holes in flat roof coverings or unpainted, rotten timber. Try and identify the source of the problem as then the necessary repair will be obvious.
Cavity walls have air gaps which break up the inside of the house from the outer brickwork. Dampness can appear if the cavity is filled with debris or some insulation. To resolve this open up the cavity and make sure it is clear.
Solid walls in older buildings take in water which is then evaporated in warm weather. For this reason the walls need to be able to breathe. When considering using coatings such as hard render or special paints, take advice from a chartered surveyor. In older houses, the walls were often ‘dry lined’ with lath and plaster on timber battens. This is to create an air gap which is much like a cavity wall. Dampness can penetrate through if this is removed so use plasterboard to create a modern form of dry lining in its place.
Types of Damp - Rising Damp
If there are damp patches and stains up to about one metre up the wall, it is more than likely rising damp. It will spread higher if it goes unchecked and it has not been treated. Check if the brick is wet, if there is mould present or if there is any rot in the skirting board. Other symptoms include lifting wallpaper or soft plaster.
Installing a damp proofing course is usually the most common treatment for rising damp. This is done by removing the damp skirting boards and stripping away plaster to expose brick of up to one metre. A silicone based chemical is then injected into the brickwork after drilling holes into the wall. A barrier against damp is formed as the chemical seeps through the brick and mortar. Finally sand and cement containing a waterproof additive is plastered onto the wall.
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