Manhole where I want to put my extension. How big of a PITA is it likely to be?

[Belleende]

We are scoping out the possibility of extending our house. The only option is to extend to the side, but there is a manhole into the mains drains where we want to build.
In the picture we want to extend out to the wall with the window is, which would put the manhole part in and part out of the house.

Anyone know what the options might be to deal with this, and how much of a pain/£££ it is likely to be. Much obliged, ta.

I would expect it to be a problem - I'd get advice before you do anything else.

We had this and none of the builders who came to quote seemed concerned. It was moved as part of digging out the foundations etc so I don’t remember a massive fuss about it but check with your own builders

We had a drainage hole where our extension is.
It's now in my utility room, with loose tile cover, groted in - you don't really know it's there.

We had to apply to our local water authority to move ours - think was about £800 about 9 years ago and we had to submit drawings in advance, but wasn’t a huge headache in the big scheme of things

Our manhole was moved and they put special foundations over the top.

The only annoying thing was having go to the water company to get the survey sorted.

It depends on who owns the sewer - if it's private or part of the public network, unfortunately just because it's on your property doesn't guarantee it's yours
It can also be shared with a neighbour which requires their consent

Good starting guide here https://www.planningportal.co.uk/info/200130/commonprojects/15/drainssandsewers/2

Some indicative costs here www.priceyourjob.co.uk/drain-removal-for-extension-cost/

We had this, no drama at all

You used to be allowed to cover it and keep an access point within the building. If it is shared/not yours, you will have to pay for the water company to move the piping and manhole cover. It will slow up the planning process, and will cost more.

Lift it up to work out where the pipe go to and from. Its more of a problem if its connected to your neighbour. You will need a buildover agreement from the local water authority which can take some time for them to do. A competent builder won't have much of a problem moving the inspection chamber but it will cost a few grand. Your architect or designer can advise you.

Thanks all, I am pleasantly surprised. I was fearing it may be a show stopper. We will of course get advice from people who are not just randoms on the Internet, but for a bunch of randoms you have done well.

We had an extension built over a drain (sewer) it did only relate to our property. They putting in 'bridging foundations' (I think that's what is what called) over the pipe, and relocated inspection cover. Didn't seem a big deal to the builders. Building department inspected it - all OK. Don't know what it cost as it was all part of the extension cost.
I think probably the most important thing to establish is if it is shared, or not yours at all!

I don't think you can build over the pipe nowadays. It has to be rerouted, in agreement with the water board.

Since southern water took over ours, it would have to be re routed as it can't be built over, I don't know it its the same with your water Authority .

Since 2011 some private drains became the responsibility of the water company. Here is Thames Water's explanation:
Thames Water

If it is a public sewer, you will need to get a build over certificate, as I understand it.

As the bit we need to move remains private, we are having it moved, and have been quoted £1,000

Phew, looks like we were lucky but it was 20 odd years ago...

It’s mostly bollocks op, but definitely not a show stopper
Talk to a decent architect regarding your proposed plans, presume you would be doing this regardless, the water boards primary concern is access to the drain and legislation has changed quite recently

As others have said it depends if it’s a private or public drain. If public you will need a build over or diversion agreed with local water authority. This might need a couple of new Manholes

oops posted too soon
... new manholes each side of your extension to maintain access to the pipes for future maintenance. Adjustments to foundations will need consideration to prevent damage to pipes. If it’s private you can basically do what you want but bear in mind any future issues are your problem to deal with not the water authority. I would have thought any decent builder/ground worker would know stuff like this and be able to advise. You may need drawings/calculations from a structural/civil engineer to gain approvals from water authority and/or building control.

If you're unsure of what options are possible, you can see if you can get a consultation with an architect for their advice & suggestions. I know that www.homeandmaker.com do free ones over the phone

Your water authority may also require a camera inspection of the drains.