Don't ignore damp - it can do serious damage to the structure of your house. Lots of different factors can cause it, and you need to find out what these are before you try to cure it, or you may treat the wrong thing and make the situation worse. Any remedies that involve opening up external cavity walls or fitting a new damp-proof course are best left to the professionals. And if your home is in an area that's prone to flooding, there are a number of precautions you can take to protect it.
There are three main kinds of damp: penetrating damp, rising damp and condensation. If you're not sure which kind you have, check the symptoms of each - and find the moisture levels in your home by using an electronic moisture meter.
Penetrating damp is caused by water seeping through the walls at any point (as opposed to rising damp, which is confined to the lower part of ground-floor walls). You may see damp patches appear when strong winds drive rain against the wall of your house, and disappear when the weather improves.
A semi-permanent damp patch can be caused by a leaking gutter or a crack in the render. But if a whole wall is showing signs of damp, it may mean that old bricks have lost their weather proof facings and become porous.
Penetrating damp is less likely to affect your home if it has cavity walls. If water does cross the cavity, it's usually because mortar has spread onto a wall tie.
The flashing sealing the joint between your chimney stack and roof may have cracked or become dislodged, allowing water through the joint. You'll need to refit the loose flashing, or if it's damaged, replace it with the same type of flashing or a self-adhesive flashing strip.
Blocked or broken gutters will send water gushing down your wall, and possibly saturate it. You'll need to clear your gutters or repair the damaged ones.
A slipped, broken or missing roof tile or slate is letting water come through your roof. You'll need to replace the tile or slate.
Old bricks can become porous and let water penetrate though the wall. Replace the bricks, or repoint and treat the area with exterior silicone water-repellent fluid.
Cracks in brickwork or damaged pointing in the joints will allow water through your wall. You should replace the damaged bricks and fill any gaps in the mortar.
If your brickwork isn't causing the problem, mortar on a wall tie in the cavity could be bridging the gap and allowing water to cross to the inner wall. The only way to solve this is to remove some bricks, inspect the cavity and rake out or chip off any mortar on the wall ties.
Some mortar might have fallen out of the gap between your wall and window frame. Try sealing any gaps with a flexible frame sealant.
Your exterior window sill should have a drip groove on the underside to stop rainwater running under it and into the wall. However, if this groove is filled with layers of paint, water can run onto the wall. If this is the case, clear the groove. But if there isn't a groove, glue and nail a hardwood strip (about 6mm square) to the underside of your wooden sill about 35mm from the front edge. This will stop water from reaching your wall, and you can paint it to match the sill.
A door in an exposed position is more weather proof if it's fitted with a weatherboard. So repair any rotten parts of the wood, and fit a weatherboard if necessary.
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