Drainage next to an external house wall Drainage and wastage systems and plumbing help, advice and answers

[dodiy]

Hi, This question is regarding drainage next to an external house wall.

I am having an area next to a south facing wall paved and decked. The finished height of this area will be one brick course below the damp course. A small retaining wall has been built six inches away from the external wall forming a small trench. There will be a 5 inch gap between the external wall and the decking/paving.

If the paving and decking is either sloped away from the house or towards a gully is it safe to leave any rain water that runs down the external wall and into the trench to drain down into the ground next to the footings?

Many Thanks Dodiy

[marrtin]

Can't see as you will have a problem as long as the ground is porous and the water will not puddle. Let's face it, there is little difference between the two levels. If by chance you have a problem in the future, maybe an accodrain will be needed, but I can't see it.

[peter the plumber]

You know keep looking at this post and there something wrong.

I think there a guttering issue.

But I am having a hard time visualizing this set up.

I am sure it will come to me.

[dodiy]

Thank you for looking at my posting.

I've tried to produce a sketch of the setup below (ignore the full stops, they just help retain the spacing when I submit the reply). The roof guttering is correct and water tight. My reference to water running down the wall is the amount that may hit the wall below the guttering. I have seen diagrams with this setup recommending that the water be directed to a gully, however the nearest gully is to high. Will the drainage holes in the bottom of the trench be a sensible option for this work around?

.................................|External wall
.........Damp Course ->|
.................................|................ ___________
.................................|................| Paving level
.................................|................|
.................................|................|
.................................|_________|
.................................Trench with dranage holes in the bottom.

[marrtin]

Hey good diagram!

As long as the paving is below the level of the damp course it will be fine. Even if the worst happened, and you temporarily had a 5" wide moat, the excess would still drain away before the damp course was bridged (which is the important thing).