Walls adjoining houses - a source of damp

Many homes have garden boundary walls that butt into the main external wall of the house. The continuity of the materials can look really attractive, especially where it is an old stone wall. There can be complications though with the junction between the two structures.

We look to keep our houses dry and free from damp, but we do not expect the same from our walls. So we tend to turn a blind eye to the water that seeps into the garden wall, whilst desperately trying to keep water from entering the wall.

This has led us to applying waterproof render to our house walls and nothing on the boundary wall. The trouble is that if there is no capping on the garden wall, water will seep into it and this can then be transferred through the junction of the two walls and thence behind the water proof render.

This is normally 'cured' by injecting silicon vertically into the house wall, but it stands little real chance, especially in stone. So what to do?

Well, ideally your house walls are treated with lime render and so can breathe and let the water out, however this is making the lime do a lot of work. The best two scenarios is that you either reduce the amount of water entering the garden wall in the first place, via a simple capping system; or that you create a physical gap between the two walls.

If you choose the latter then be aware that the house wall would be giving the garden wall some inherent strength and stability and so this will probably have to be replaced by the use of a buttress type support in order to stop it all from falling over!!