Laying underground soil pipe in floor insulation.

[rssteve]

Is it acceptable to run underground soil pipe ontop of my concrete slab but under my 75mm screed, I plan on using 180mm insulation. Im struggling with heights and need to add a gully on the opposite side of my planned rear extension. Top of pipe at existing gully is only 160mm to ffl, so not low enough to go below the planned slab, and can't run around the extension as it would be above outside ground level.

 

[noseall]

Just plan your over-site differently. Fit the insulation under the concrete slab and run your pipe through the insulation layer or MOT layer.

 

[rssteve]

There isn't room. Currently the top of the pipe is 160mm below ffl, this is at the existing gully, I need to get to the other side of a 5m extension to connect an old shared drain pipe between me and my neighbour. Currently this in a gully that is piped to an embankment at the edge of the garden and just pours down it, and may have been the cause of a small landside last year. We can also not have a soakaway due to the embankment. I could probably get away with a 50mm slope on the soil pipe at 5m in lenght, but this still means the top of the soil pipe will only be 110mm below ffl at one end of the extension. Not enough for slab and screed ontop. I though it would be better to lay slab below in one piece, then 180mm insulation so the pipe has some insulation all the way round it at both ends, then screed on top. Im only in the planning stages but I need to know where I stand as this is my only concern at the moment.

 

[noseall]

Practically speaking the pipe will be ok to pass through the insulation layer. I'm not sure how it would be viewed on a thermal basis, in terms of a pipe with cool running water passing through it so close to the surface of the screed and without any inso' above it.

You will have to ensure that it is bedded in and not protruding into the screed layer otherwise it could cause a distinct weak point.