Trench Fill Foundations and 9 inch Thames Water Pipe

13 May 2010
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United Kingdom

I have planning permission for a double storey side extension and single rear on my 1920's cottage. The Building Regulation app has been more or less approved with trench fill foundations. I have just dug a trial hole and as I had very much dreaded I have come across a 9 inch surface water sewer which is directly below where my foundations will be.

This 9 inch pipe I was aware of, but i was under the impression it was further away from my foundations than it is. I have a buildover application with Thames Water in progress.

I do not want to reduce the size of my extension, but it has been suggested that it would be possible to cantilever over the pipe in order to keep the original size of the extension. It has also been suggested that pile foundation (or mini piles) which would be cantilevered over the top may be the way to go.

I heard that Pile Foundationing is very expensive... would it be possible to move the trench fill foundation over (to miss the pipe) and cantilever over that.

I dont believe this will cause an issue to Thames Water should they need access to the pipe.

Thanks for all your help.

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Is there an easement in place for the pipe?

To be honest your engineer should be providing a suitable build over option to be combined with your application.. be it piled with cantilever reinforced beams or bridging..

That said the few grand extra that may cost might outway the hastle of moving the whole thing away from the pipe.. get some quotes when you have an idea of what is being proposed..

ps. some idea of size of extension etc plans and so on help.. we dont know if this is a toilet or a castle you are building

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