Building on a manhole cover: what is a 'build over agreement' and will this ruin my plans for a new conservatory?

I'd like to build a conservatory but there's a manhole cover on my patio that I would need to build over. Can I legally do this and if not, what are the alternatives?
Shutterstock / U.J. Alexander
Piers King10 March 2020

Question: I am looking to build a conservatory at the back of my house but there appears to be a manhole cover to the side of the patio that I would be building on.

Is this something that I need to worry about?

Answer: The manhole cover is likely to lead to a public sewer which may well serve a number of other properties in the area.

Any construction work near a public sewer is heavily regulated due to the danger of damage being caused to the sewer. Any building over a manhole cover is prohibited.

In addition, if you are building anything within three metres of a public sewer, you would require the consent of the local water authority, who may require you to enter into a “build over agreement” to ensure continued compliance with their requirements.

The building control department of your local authority would also need to be consulted prior to any works being carried out.

It would be advisable to consider whether the plans for your conservatory could be altered so that the construction is at least three metres away from the sewer or manhole cover.

Alternatively, you could ask the local water authority to remove the manhole cover and divert the sewer.

However, this would be at your cost and is likely to be very expensive.

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.

If you have a question for Piers King, email legalsolutions@standard.co.uk or write to Legal Solutions, Homes & Property, Evening Standard, 2 Derry Street, W8 5EE.

Questions cannot be answered individually, but we will try to feature them here.

Piers King is a solicitor in the property department of Streathers Solicitors LLP.