by Russ Ware
In the UK we see a massive 25,000 gallons of rainwater a year, so it is no surprise that one of the most common problems in our homes is damp. Damp is usually fairly easy to fix, but can sometimes be an indication of a more serious problem. This guide aims to help you find and solve the main causes of damp.
If you notice localised damp (in one area of one wall for example), often the cause is a leak.
Check the guttering and downpipes in the affected area first; these are classic causes of localised damp. Make sure they are clear and running smoothly, as well as that all joints are tight. If not, seal or replace.
If the damp is below a flat roof, or a roof channel, check that the felt is sound.
Finally check flashing and tiles (around the chimney stack if the damp is on a chimney breast).
If the damp is below a window, check the windowsill and window frame. Badly fitting frames can let damp penetrate the room, as will a bridged drip groove on a windowsill.
If none of these seems a likely cause, make sure the damp proof course is not bridged. Earth, etc, piled up against the house could be allowing water to penetrate above the damp course.
Spalled or cracked bricks and broken pointing can be another entry point for water. Once the face of a brick is removed, water will soon work through the porous bricks.
Damp might not always be coming from outside your house.
Condensation is another classic cause of damp problems, especially in rooms without adequate ventilation. Condensation is caused when warm air meets a cold surface (such as a metal window frame of badly insulated wall).
If you cannot improve ventilation, you might need to improve insulation.
Condensation on walls can be fairly easily prevented by wallpapering the wall in question with polystyrene-backed paper, fixed with fungicidal adhesive. You can also use a polystyrene lining paper. Make sure the wall is as clean as possible before starting this job.
Is the condensation is on windows, a cheap option is secondary glazing. This is cheaper and easier that getting all new UPVC windows. There are plenty of plastic kits available.
If damp in walls seems worse at the bottom of a wall than the top, your damp proof course is probably to blame. Once you have checked it has not been bridged, and assuming it has not, your next option is replacing the whole damp proof course. This is usually a job for the professionals! Using a contractor will mean you receive a damp proofing certificate, which is useful when selling your house.
Damp in the middle of a solid (concrete, etc) floor is also a sure sign of compromised damp proofing. Again, this is a job for the professionals.
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