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Posted: Sat May 28, 2011 10:04 pm
by bars03
Hi
I am planning to build a 4x4m rear extension. Foul and water sewer pipes run parallel to the rear of the property (approx 1m away from rear wall). The sewers are approx 1.3m deep.
I was just seeking some advice on how best to approach the foundations for this build? I was initially looking at a trench fill foundation. Would it be fine to build a concrete footing either side of the sewer pipes, fill in the void with gravel and lintel over? How much of a gap should be left between the pipes and concrete footing?
Cheers
Posted: Sat May 28, 2011 10:55 pm
by msh paving
bars03 wrote:Would it be fine to build a concrete footing either side of the sewer pipes, fill in the void with gravel and lintel over? How much of a gap should be left between the pipes and concrete footing?
Cheers
On no account do you stop/start footings,you will have to dig upto and under the pipe and a carry on along the footing,check with building control on how thick the concrete will need to be 225mm min.depending pipe dia. and at 1.3m deep you may be able to wrap with compressable fibre material and concrete over them, but this is for qualified people to decide,other wise it will be concrete under pipes and lintol over them MSH 
Posted: Sun May 29, 2011 12:40 am
by lutonlagerlout
depending if it is a public sewer we have many times just dug 300MM past the invert level then shuttered eith side of the pipe approx 300mm back either way
but as mark says your BCO decided#s this
LLL
Posted: Sun May 29, 2011 9:09 am
by seanandruby
The pipework should be about a metre away from any structure. We have before now had to cantiliver over the pipework, or, lay a raft slab over it, or divert the pipework. Depends who the bco is.
Posted: Sun May 29, 2011 9:34 am
by Wideboy
I know I'm not an expert but if I can add my two pence worth It would make sense to check the condition of any pipe work going under your extension to make sure it's all OK you don't want to be digging the floor up a later date to rectify a problem that was easy to do whilst it was all dug out!
Posted: Sun May 29, 2011 12:10 pm
by A.V.A.G.O
Thans bars03 you saved me asking the same quetion, I too plan on putting a 4x3 extension on the back of my house, I believe I ave to go down 2m to get to my drain,
So it looks like I will need to go deeper 300mm below the pipe and run the concreate in, Do I then use trench blocks and span the pipe with a lintel and then finish the footings off to the correct height ?
thanks for looking