Waterproofing walls, the damp proof course DPC

Waterproofing walls, the damp proof course DPC

WALLS, Dealing with damp

Rising damp is a problem with many older houses and buildings in London; the damp-proof course wasn’t adopted until late in the 19th century, and cavity walls were a 20th-century device.

The problem has become worse as big open fires are abandoned – these kept up sufficient draught to evaporate moisture from inside rooms and sweep it up the chimney. Without them, damp may cause damage.
There are some ways of keeping it out or at least keeping damp-stains off the plaster and wallpaper.
damp wall

Bricks suck up water like blotting paper; make them waterproof and damp will stay down at ground level. Builders’ merchants sell waterproofing solutions that, painted on liberally inside the damp wall and out, will, with luck, soak through, join up in the middle and form a waterproof barrier. Painted on the outside these solutions certainly help keep out driving rain, and once dry they are invisible. A more expensive but thorough treatment is to drip silicone waterproofing solution into the wall through tubes drilled into the bricks.
You can buy the solution and hire equipment, but it’s best for a specialist firm to do it.

Sometimes used with the dampproof solution method: porous clay pipes set into the wall where a damp-proof course
would be if you had one. They slope down slightly from inside to outside (where small grilles keep out the rain and inquisitive mice) and are set in a porous mortar. The idea is that moisture seeps into the pipes through the porous walls, then trickles harmlessly down the slope to the outside of-the wall.
No job for the amateur; your builder may be able to do it, or will more likely refer you to a
specialist firm. The job should last for at least 20 years. A good firm will offer you a 20-year guarantee on their work.

Electro-osmosis goes back to first principles to cure damp: what makes damp climb up a wall ? The answer is that there’s a minute difference between the electrical charge of the wall and that of the earth beneath it; take away the difference in charge and there’s nothing left to power the climb of the water.
Electro-osmotic damp treatment consists of driving small copper rods into the wall roughly where a damp-proof course would be, joining them with a copper strip, and joining the strip to an earth rod, a metal spike sunk well into the ground. Amateurs have done it, but it’s worth getting a professional job and a guarantee,usually 20 years.

Cutting right through the wall to insert a new damp-proof course sounds drastic, and isn’t a job for the ordinary householder to tackle. A special saw is used to cut through the mortar or bricks, a short length at a time, a damp course inserted and the mortar restored, before moving on to cut the next section. The completed work is usually guaranteed for 20 years or more. All these systems are fundamental cures: they stop damp getting into the wall. None are cheap. If it isn’t possible to use them, for financial or technical reasons, you will have to leave the wall damp and concentrate on protecting the inside of the rooms. In the picture below, modern DPC for cavity walls.

dpc kitchen extension walls

Contact us for a quote for your damp proofing problems.