Drain run at bottom of foundation

[garyo]

I have a clay drain run that crosses perpendicular to my foundation. The invert of the pipe is 50mm higher than the bottom of the foundation. Is it acceptable to box this in with 22mm OSB, fill with pea shingle, then mass-fill over the top without lintelling, or should I position some rebar lengths or PSC lintels over the top before mass filling? I expect the span would end up being ~300mm.

I don't particularly want to shutter all the way to the top of the foundation for fear of it leading to a weakness in the run that might lead to brickwork cracks through differential settlement of either side of the foundation.

Thanks

 

[noseall]

Some BCO's will accept a box formed over the pipe, giving a clearance margin of say 100mm around the pipe. Is it a sewer or is it sole ownership?

The foundation should always be deeper than the pipe.

 

[garyo]

Thanks. It's a single clay 100mm drain pipe that takes the foul from our downstairs loo, so sole ownership.

The foundation is just deeper than the pipe by around 50mm.

 

[martin hill]

My drain inspection chamber is outside my french doors on the extension. When built they dug the pipe out and replace with a plastic one and poured the foundation. Then up with foundation blocks with a gap round it with a lintel cut into two and placed over the top with clearance. Dont think they filled in with anything like pea shingle on the foundation just a pea trench on each side if that helps.

 

[noseall]

fill with pea shingle

As above - noo need for shingle, keep it clear.

 

[garyo]

Cheers chaps. I'll box in and keep my fingers crossed.