Cavity Walls

Another great invention by our forebears for resisting moisture penetration into the home is the cavity wall.

The idea of the cavity in traditional houses is to separate the outer skin of brickwork from the inner skin in which we live. Any rainwater hitting the outer wall can penetrate the brickwork or pass through the mortar joints. On reaching the inside of the outer skin it runs down the inside face and at the bottom of the wall is guided back out through the weepholes or cavity trays.

The idea first took hold around 1927 and is easily spotted by checking out if the wall has header bricks which go through from one side of the wall to the other. If it does have headers spread across the full width of the wall then there will be no cavity and the house was built pre 1927. If there are only stretcher bricks ie you can see their full length from the side then, you almost certainly have a cavity wall.

Problems with cavity walls can arise from poor quality builders who let mortar build up in the cavity which bridged it letting damp across in heavy weather. Also some cavity insulation can bridge the cavity. Therefore it is important when having cavity wall insulation done that there is good protection in place for faulty or poor workmanship, especially where the wall is exposed to the weather.

In new houses the cavity is insulated with a fibre which is tied to the inside of a wider than usual cavity to ensure the water gap is maintained.

Should you need any low cost advice on your house construction drop us an email at