Manhole under where I want my extension to go!

[manholewoes]

I've been dreaming in an extension to my home for ages, have had architects round this week and they mentioned the manhole, which I hadn't really noticed as it's in my patio area and pretty well disguised.

I've pulled out the plans from when I bought the place a few years ago, and the plan seems to show that it's a shared sewers and I didn't realise that not everyone has a manhole in their garden.

I've attached a photo of the plans, pink arrow is my garden. The plans show that the manhole is what looks like a few metres
from my house, but it is about 1.5 metres away, I can't really extend a good amount (I originally wanted to go out 3.5 metres) to create another room.

Help! Do you think I might be able to get a build-over agreement (southern water) I know the only answer is to ring them, but it's Sat night and their phone lines aren't open and I'm not going to be able to sleep worrying about this!

Here's the plan

You may need to move it?
They should come out and have a look.

We moved our and rerouted the clean water pipe and then got it signed off with ST and building control.

Presumably I can only move it along the sewer line? Which doesn't help me because it's already near the edge of my property (again it doesn't look like that on the plans, but it is in reality)
I can only think I can pay to have the whole section of that sewer line moved, but that would be ridiculously expensive for me and disruptive to my neighbours.

It's a shared foul pipe

It would be really expensive and inconvenient to move imo. I wouldn’t even attempt to extend over a manhole, it would make your house unsellable. A build over agreement allows the water company to access the manhole even if it means ripping up your floor or demolishing your extension if they have to. That’s a deal breaker for many buyers.

You can’t get decent advice here. You need a surveyor and to talk to Southern Water but basically (and I have done this) it should be entirely possible to build an extension provided you either move the manhole or include it in the floor of your extension in such a way that it is accessible. It will depend on the routing of your neighbour’s pipework.

But totally doable.

yeah I got a buildover agreement to move a chunk of the sewer that was where my foundations needed to go. it was extra paperwork and a load of photos during the relaying process, but not too bad. Your architect should be able to advise, or failing that i got in touch direct with Thames Water.

I moved a 10m chunk of sewer was several £k but very worth it.

I'd look to get it moved unless you don't intend on selling the property. As pp if you build over it it will put buyers off due to the access needed to it.

My mils extension has a manhole cover in it. She's got some kind of wooden floor and a wooden manhole shaped trapdoor thing. Apparently you can pull it up to get down to the actual manhole but I don't know what it actually leads too or anything like that. It doesn't look out of place or anything and most people assume it's basement access

@colouringinpro you mean £6k?
Was that fairly recently?

Surely moving the sewer pipe would involve digging up all my neighbours gardens which are connected to 'my' pipe?
So new gardens/fences for them & the cost to the water company?
It's not worth it.
I'm pretty gutted, amazed I'm not crying, but thought something would come along to piss on my dream

Can't they just loop it along your property to a more convenient location for your extension? They don't have to be straight I don't think?

Some friends had to reroute their sewer but no one else’s, they are in a long terrace. Added about £2k to their build costs.

Whatever you plan depending on size of project you need to have a few thousand pounds wriggle room for unexpected things. For example we’d budgeted for a certain depth of concrete foundations- then once foundations were dug the council inspector came round and advised to get building regs sign off they needed to be deeper due to tree roots. Cost us about £2k extra. Other changes also added on more costs so we ended up with a shell we had virtually no money to fit out. We managed it and made compromises and I never did get my granite work surface or self cleaning and opening skylights but we did get a lovely space.

There is nearly always a way forward but you need to be determined and have deep pockets. Sometimes it also means waiting a bit longer or compromising on some details if the costs are not immediately in your reach. Please don’t loose sleep over it.

Can you extend elsewhere? Loft? Basement? Garage?

Public sewers are a absolute nightmare when it comes to extensions. We have one and whilst we didn't need to move it, we needed to plug into it with a new drain. The architect advised to not even go there. It was far cheaper to lay a private drain right across the back garden and plug into an existing private drain which seemed crazy.

Our neighbours though did an extension and didn't realise (god knows why not) they were building our the public sewer. Work stopped for 2 months pending bringing in the water company. Neighbour described it as a total utter nightmare which they did sort out, built over it BUT what she said they were lucky with was there wasn't a manhole

If you have an access point in your new build you clearly need to be able to access it which limits your options.

You really do need specialist advice but also look at this from SW Water. https://www.southwestwater.co.uk/siteassets/documents/buildoverrguidancenotes.pdf

We built over and have an access point under our cooker. It was just lucky that's where it ended up, but as PP said - you can incorporate a trap door type arrangement to conceal if it's in the middle of the new room.

I'm pretty sure you are not allowed a manhole cover inside your house anymore- although I guess each water board is different.
Thanks for all the advice, my neighbours have just built an extension right up to their manhole cover, I'll ask them how they got away with it!
My extension plans will be seriously compromised by not using the space over my manhole, basically will mean you have to go outside to access my utility area, which wouldn't be great, plus lose a big chuck out of the new living area.
See attached photo of my rough sketch.
Existing manholes and shared waste pipe in pink - my possible solution in yellow.
This would involve digging up 2 neighbours gardens, which might be ok because one (on the left in sketch) is currently building - but will put the house in the market shortly my neighbour on the right wants to build an extension in near future - and neither neighbours have patio etc down and are not too garden proud. (Although there are trees on right neighbours too, just to complicate things - but they need to cone down anyway if the neighbours build)

I had an existing manhole in my house when I bought it. It backed up on numerous occasions but didn't overflow. I moved it.
It was easy, building control and waterboard both had to agree as I was re doing the drains for the whole house and moving the bathroom. A new floor had to be laid in kitchen but that needed doing anyway. Cost 6k in total with not much to show for it but its done.

I think you are being too gloomy given that you haven't had any professional advice yet.

Have you got/will you get proper plans drawn up? I'd do this because it will make it a lot easier defining the scope of work for the builder, and the surveyor will tell you what to do about this.

if you get 2 or 3 quotes from surveyors, they will likely all come and look, and give specific advice about the drains.

Filka I'm not too gloomy, but I'm on a tight budget and a tight timeframe and considering I haven't even chosen an architect or had plans drawn up, I'm gutted to have hit a big £ problem so quickly.
Because it's the weekend I can't ring the water board/surveyors etc, and I don't want to bore people in RL with this, so I've turned to MN!
I've been dreaming about having this extension for a long time, and not been able to think about it seriously until now, it will make a massive difference to my home and I plan to stay here for a long time, so it's very important to me, I know it's trivial in the scheme of things, but not to me right now.

Sorry if that sounded snippy, it wasn't meant to, I know it will probably work out ok in the end, but I really want to stay in this house, the location is perfect for me, but if I can't extend the house won't serve my and my children's needs for much longer (already bursting at the seams)

You may not need to dig into your neighbours garden , can't see why you can just take the pipe from your garden and extend it out to a new man hole and bring it make all in your boundary.

We discovered ours 2 days after the builders started work so had no choice but to move it. This was 25 years ago and added £1500 to our budget which was a bit stressful but we had no choice and managed to incorporate it somehow.

Ouch French!
Like this @Pickpick101 ?