Can we extend our house over a manhole?

My partner wants to extend our house but there is a manhole in the way. Can we do that? And will the water company pay for any of the work?
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Unhappy couple with burst water main in their house
© Merrily Harpur

Question: My partner wants to extend our house but there is a manhole in the way. He says that it's no problem because he can build over it, so the cover will end up in our new, bigger kitchen.

I'm not happy about it. Can we do that? And will the water company, whose cover it is, pay for any of the work?

Answer: The building control department of your local council is actually responsible for the control of building over sewers but must consult with your local water authority.

You and your partner must obtain the agreement of the local water authority if you intend to carry out any building works either over or within three metres of a public sewer.

It is not permissible at all to build directly over a manhole or a pressurised pumping main.

You should consider changing the plans for the extension so that it will be at least three metres away from the public sewer or manhole cover, or you could have the sewer diverted.

The local water authority could do this. However, it would be at your expense. You should contact the water authority to see if diversion is possible, and to ask for a quote for the works.

"Build over" agreements and strict control of such works are necessary because the extra weight of a new building over a sewer could cause the sewer to collapse — which could result not only in structural damage to the new building, but also in drainage problems for neighbouring properties.

Additionally, access to manholes must not be hindered in case repair works or maintenance is required.



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If you have a question for Fiona McNulty, email We regret that questions cannot be answered individually.

These answers can only be a very brief commentary on the issues raised and should not be relied on as legal advice. No liability is accepted for such reliance. If you have similar issues, you should obtain advice from a solicitor.



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