Build Over Agreement Query - Sewer pipe running through proposed extension wall

25 Mar 2024
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United Kingdom
Hi everyone, great forum with a wealth of knowledge. Just have a query regarding a build over agreements. Majority of cases I've come across seem to be dealing with sewer pipes which reside in the foundations of extensions. Looking to proceed with an rear extension where the garden is on a drop so and not level with the rest of the house.

That means the lateral sewer pipe which is the responsibility of the water company, runs across the back of the property just below floor level so won't be any pouring of concreate over it and main thing will be the pipe passing through one of of the proposed walls of the extension before it carries onto the neighbours property.

Just wanted to know if there's any major technical details to consider when building over it in this scenario. The extension will have a suspended floor and then stairs down to the garden. Plan is to have storage area under the extension where in theory the sewer pipe should be accessible if required.

With that in mind, the sewer pipe will pass through one of the walls of the proposed extension so will have to build around it. Sewer pipe will have a lintel placed over it and believe a 150mm reinforced concrete lintel should suffice. Would a 50mm gap between the pipe and the blocks around it in this case suffice and what should the gap generally be filled with?

Working with the architect and builder but like to generally gather opinions.
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