Retaining wall for patio - drainage - Retaining wall for patio - drainage

[hja90]

Wondering if someone could provide some insights into how I can install the drainage system properly for a new patio and retaining wall. In short, I recently moved into a new home, there were three layers of patio built on one another, higher than the DPC for the Annexe - this resulted in serious damp issues in the building, rotten floor boards etc.

I have taken all of the patios up and dug down to my required depth - I am going to put Aco drains all around the Annexe and paint the brickwork with Bitumen to avoid any further damp issues, the patio height will be atleast a brick below the DPC line on completion.

My question comes around drainage - I am building a 9m long, 9inch new retaining wall with a brick skim, it is being tied into brick work either side of the garden, I want to ensure adequate drainage, therefore I am installing a perforated pipe behind the wall and the aco will run horizontally across the length of the wall from above. The wall will be around 60cm high.

I am stuck on where the water should drain off too, i want to run it from the patio underneath the footing of the new wall and out to the back of the garden. Is it bad to have the drainage running underneath the concrete footing? Or is there an easier way and more cost effective way to channel the surface water away from the patio without having to go under the footing. The wall will essentially run horizontally across the garden from the fence to the flower bed wall. So its not like i can have the drains come out from the side, as they will be tied in to brickwork at both sides, it needs to go through the wall or under from what i understand.

Anyway, some guidance would be widely appreciated.

Thanks

[Tony McC]

No real problem running a drain beneath a footing. The usual method (assuming the pipe isn't too deep) is to envelop the pipe in concrete that is part of the same pour as the footing, and then have a rocker joint each side.

[hja90]

Very helpful, thank you! Although, I think i've decided to let the patio naturally drain off the edge and onto the grass, Its a patio of around 60 sqm and 10m wide, the finished wall height will be 60cm and the patio will sit nicely on top. The fall will be away from the house and onto the lawn, we have quite good soil so I believe the surface water should drain sufficiently away, the gutteRing I'm going to tap into a water butt so it's only surface water from the patio draining off. Do you think this will be ok?