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Extensions

Foundations within 500mm of sewer

Anonymous user 23/02/2024 - 3.25 PM

I'm in the process of sorting all the pre-work for my extension. Looking at my drainage search when I bought the house there seems to be a gravity sewer running along the garden horizontally, running through all the terraced houses. I'm looking into my water authorities rules and one is the foundations/wall can't be within 500mm of the sewer. I don't really want to lose half a metre. I did read you can bridge over it with lintels? I'm not sure this will be possible as looking at the diagram it is slightly under my garden, the garden is raised about 2 metres, my extension will be ground level and will just butt up against this garden wall. @ASF unfortunately bridging isn't a possibility as the pipe or part of the pipe is under 2m deep of garden as per picture.

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5 Answers

J. Contracting LTD

Rating: 5 out of 5
Waterlooville
The water authority will not design your foundations for you - they will stipulate their requirements for compliance which can usually be found online. I recommend you employ a structural engineer to design the foundations in compliance with the water authorities build over conditions - then apply to the water authority for a compliance notice with the detailed drawings and calculations attached. Anything is possible - cost, is as usual the limiting factor.
Answered1 August 2019
28

A S F BRICKWORK & BUILDING SERVICES

Rating: 5 out of 5
Bristol
you actually can bridge over them very safely if it is done correct, your water board company will give you instructions on what they require and will want to inspect the bridging work before any concrete is poured they usually require the footing to be hoarded up either side of the pipe, then the concrete lintols fitted, the pipe must be backfilled with shingle, then on top of the lintol they require insulation then a further lot of shingle on top of that , this is how I have always done them according to Wessex water instructions
Answered1 August 2019
3

Anonymous user

I agree with both responses. Unfortunately you have discovered what a contingency is for. This is going to be an additional cost and normally requires foundations to go lower than pipe in the event the pipe leaks.
Answered30 August 2019
0

Anonymous user

We recommend that you appoint a structural engineer or architect to draft a drainage bridge plan and then apply for a bridge over agreement certificate from Thames Water. You will then be able to proceed with your proposed build without any complications or delays. Regards,
Answered24 September 2019
0