French Drain Advice

[JezH]

Hi All,

I have some damp caused at least in part by a concrete path in the alleyway to the side of my house.

I want to dig a french drain but have read you should keep this away from the bricks but dont see how you could do this? I was going to do it in such a way that the gravel was against the brick?

Also is how much diffefrence does adding a perforated pipe make? I was not going to bother doing this as I am not dealing with large volumes of water, just the fact that the bricks never dry out.

I should add that I do not have rising damp, but the outside is around floor level and the bricks just inder the floor are very damp which has caused old joists which were in direct contatct with the walls to rot.

What I am trying to do is to reduce the damp below the dpc rather then stopping moisture rising, which I think a French Drain would help with.

 

[Tigercubrider]

i guess that a perforated pipe would be drier than the same space full of gravel.
You could buy a bit of wide DPC material ( or make some out of polythene rubble bags) to sit against the house wall. held by gravel
use bigger stones

 

[Doggit]

As the wall and the joists are below the DPC, they are always going to get wet from the foundations upwards. The french drain will help and is a good idea, but most people put gravel in, and that collects dirt, so will always track water across it. You need stones that are least an 1" diameter in a french drain with the perforated pipe in gravel set low enough below the inner joist level; but if you can't get it that low, then I wouldn't bother with it. Painting a liquid DPM on the wall might be a better idea than the perforated drain though.