Rest bend on top of, through or below foundations?

[aa44]

I have not installed drains before and I would be grateful if somebody could give me some advice.

Our new house is being built on a rocky hillside and the strip foundations (600 wide, 300 deep mass concrete with an A393 mesh 75mm from the bottom) are being poured onto what is pretty much solid rock. The bottom of the founds is about 650mm below the finished external ground level and the top about 350mm below the ground level.

There are several soil pipes that need to run down the inside faces of the walls and I would be grateful for advice on how to install the rest bends at the bottom. If I install the rest bend on top of the founds and go through the wall then the top of the drain pipe will only be about 250mm below the ground outside which doesn’t seem deep enough.

If I stick the rest bend through the foundations, then I will need to join the rest bend to another length of pipe in the foundations. (I assume that this is OK as long as I have some sort of joint shortly after the foundations, i.e. I don’t have a 6 metre length of pipe terminating in the foundations!). The soil pipe needs to be close to the wall on the inside so the top of the rest bend would go down through the top of the foundations close to the “room” side and then exit through the side of the founds on the “external” side.

Before I speak to Building Control about this, can anybody tell me if there is a standard way to tackle this? One option would be to make the foundations deeper at this point so that the rest bend could go through the wall rather than through the foundation. I guess that I would need to make it about 300mm deeper for about 1.5 metres (to allow a 600mm step overlap in the founds on either side).

Thanks
AA

 

[simonjay]

I have not installed drains before and I would be grateful if somebody could give me some advice.

Our new house is being built on a rocky hillside and the strip foundations (600 wide, 300 deep mass concrete with an A393 mesh 75mm from the bottom) are being poured onto what is pretty much solid rock. The bottom of the founds is about 650mm below the finished external ground level and the top about 350mm below the ground level.

There are several soil pipes that need to run down the inside faces of the walls and I would be grateful for advice on how to install the rest bends at the bottom. If I install the rest bend on top of the founds and go through the wall then the top of the drain pipe will only be about 250mm below the ground outside which doesn’t seem deep enough.

If I stick the rest bend through the foundations, then I will need to join the rest bend to another length of pipe in the foundations. (I assume that this is OK as long as I have some sort of joint shortly after the foundations, i.e. I don’t have a 6 metre length of pipe terminating in the foundations!). The soil pipe needs to be close to the wall on the inside so the top of the rest bend would go down through the top of the foundations close to the “room” side and then exit through the side of the founds on the “external” side.

Before I speak to Building Control about this, can anybody tell me if there is a standard way to tackle this? One option would be to make the foundations deeper at this point so that the rest bend could go through the wall rather than through the foundation. I guess that I would need to make it about 300mm deeper for about 1.5 metres (to allow a 600mm step overlap in the founds on either side).

Thanks
AA

You can have a gap in the foundations and a lintel over the pipe (one for each leaf of a cavity wall).
If there is enough depth, the founds should go under the pipe, leaving a square gap for the pipe. Fill all around with pea shingle etc. Use shuttering to keep the pipe gap free of concrete.
You can also pass the pipe through the foundations, leaving a gap all around the pipe (polystyrene or something to stop the concrete filling the gap)
Or put a larger duct through the wall and put the rest bend etc. though this.
If the pipe is cast into the foundations with no clearance around, you need rocker joints on each end - this would be difficult with a rest bend, since as you say, the joint needs to be "in" the wall.
NOTE: if the pipe is going into a suspended floor rather than a solid floor, protection from rodents entering is required - a board with a hole for the pipe and packed around the pipe with rockwool.

Lots of options. Have you got a designer / architect ?

Simon.

 

[aa44]

Thanks, Simon. I have decided to go with the rest bend on top of the foundations. There is no vehicular traffic where the drain will emerge so I can fairly easily protect it, even though it will be shallow.

Thanks again.
Andrew