How to treat rising damp

Rising damp is caused when water from the ground spreads into the brickwork by means of capillary action, rising through fine cracks in the masonry. It is usually found only in the first metre or so of the wall.

Since 1875 all new houses built were constructed with a damp course, essentially a membrane or, waterproof barrier built into the walls to prevent the problem. Rising damp can affect any property, however well treated, if the damp protection is 'bridged' - for example when a patio, path or raised flowerbed is built against the house above the damp course.

It is less common than you might imagine. However, it is often misdiagnosed by unscrupulous or inexperienced builders. Make sure the problem is not – for example - leaking guttering, faulty or leaking plumbing or condensation caused by inadequate ventilation.

Symptoms

Rising damp will almost always mean damp patches and stains up to about 1 metre up the wall. Only if it has been allowed to go unchecked will it have spread higher up.

Look at the exposed surface of the brick. Check to see if there are salts forming, that the brick is actually wet (not just the wallpaper or paint), that there is no mould present and whether the skirting board is showing signs of rot.

Treatment

The common treatment is to install a damp proofing course. This generally involves stripping away the sodden skirting board and plaster to about a metre to expose the brick. Holes are then drilled and a silicone-based chemical injected into the brickwork. The chemical seeps through the brick and the mortar to form a new barrier to damp. When that is done the wall is re-plastered with sand and cement containing a waterproof additive.

If an external feature like the patio or flowerbed is to blame, the damp can be cured by lowering it below the level of the original damp course and then allowing the area to dry out naturally by opening windows and heating the room.

The work should be of a good standard. There are thousands of damp coursing firms out there. Like any major structural work to your house it is worth getting at least two or three quotes before you commit to the work.

Whoever you chose make sure they offer a guarantee, usually 20 years, which is backed by The British Wood Preserving and Damp-proofing Association (BWPDA).