There are a number of ways that damp can find its way into the home. You may recognise it as a concentrated patch of moisture, leading to discolouration and even a funny smell.
However it is caused, ignoring it can have a damaging effect – mould might start growing on the walls, window frames can rot, and anyone living with it could develop health or respiratory problems.
Firstly though, you need to identify the type of damp you have – there are three kinds: rising damp, penetrating damp and condensation. Look at the symptoms in your home (ask an expert to help if you’re unsure) and then decide the best way forward. It’s important to get this right, as using the wrong treatment might make the situation worse.
Some will know it as the name of a popular 1970s TV sitcom, others as moisture being soaked up through the house from the ground. It will be noticeable on the lower parts of a wall, up to a height of about a metre, and across solid, concrete floors. You might also notice that it tends to get worse during wet weather, when the walls have more water to soak up.
If you have a fairly modern house, it should have protective waterproof barriers under the concrete floors (a damp-proof membrane) and in the walls (a damp-proof course), which are designed to prevent rising damp. If the building is of a certain age, it might not have either, or if it does, one could be damaged.
Calling a professional to fit or replace a damp-proof course or membrane is one action you could take. If there are just a few wet patches on the floor, then it might be that the membrane itself is only slightly damaged, in which case painting the floor with a waterproof emulsion might help here.
The damp-proof course in the walls should be at a height of 15cm. If you spot any wet patches above this height on an exterior wall, check that there’s nothing on the other side that is responsible for the moisture, such as a raised path or piles of damp earth.
While rising damp relates specifically to moisture from the ground, penetrating damp can come from anywhere. It might lead to wet patches on the ceiling or towards the top of a wall, which can signal a leak somewhere, or the bricks themselves may be so old that they have become porous, allowing entire walls to soak up water like a sponge.
If you suspect the damp is being caused by a leak, finding the source and fixing it should hopefully make the problem go away. Check that there are no leaking pipes, that guttering is not broken or blocked, there are no missing or damaged roof tiles, and that any joints are properly sealed.
If damp on walls is caused because of damaged or porous bricks on the outside of the building, it might be that they need replacing. You can try filling in any gaps in the mortar and also treat the bricks with a water-repellent product as another way of damp-proofing walls.
Other areas to check might be around the door and window frames. There could be gaps that need filling with sealant, or rotten wood that needs replacing.
In a modern home with no real structural problems, this will be the most likely cause of damp. Warmth causes moisture to evaporate into the air, and as soon as it hits a cold surface turns back into liquid, covering the wall or window with water droplets. This moisture can sometimes soak into the window frames (making them rot) or into the walls.
The solution here is perhaps the simplest form of damp proofing – opening windows to allow the moist air to escape easily. Double glazing and insulation can not only stop heat being lost in the house, but also make sure that walls and window panes don’t get quite as cold (and create condensation). You can also try using a dehumidifier, which are very easy to make at home.
Also check that there are no areas where condensation might build up unnoticed. A sealed fireplace or chimney will still have a flue running behind it, and the moist air will need to circulate. Make sure a vent is fitted to prevent a build-up. Similarly, in a loft or basement, check that vents or airbricks are allowing circulation to take place. Ignoring condensation can lead to problems and is not covered by your insurance.
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