Building over a foul sewer

Sillychuckie

Hello. I'm considering a house purchase (which we would only want, if we could extend it).
Received the following plans back from water company:



My image shows:

- Larger black outline (current property)
- Adjacent black squares (current double garage)
- Green outline (proposed rebuild/extension etc)
- Red line (foul sewer)
- Red dot (man hole - I believe, if I understand the plans correctly).
- Brown area (not our land - electrical substation).

Essentially, I'm just trying to get some idea of whether this would be possible.
I'd think so, because it would appear as though the garage already sits on top of the sewer, HOWEVER, there is a small space between the house and the garage (for garden access), and it is possible that the plans are just a little off and the sewer runs through this gap (so has nothing built on top of it).

*Sigh*
[Electrical substation, foul sewers... Perhaps this is not the best plot - but can it be done?].

Any plumbers/property builders/architects with experience able to advise? I know it might cost more (which I'm not so concerned about) - its more just whether its going to be a show stopper or not.

Thanks.
SC

Doozergirl

It would need a buildover agreement from the water provider if the sewer is shared with your neighbours - which looks to be the case. It needs to be obtained before building starts and usually involves a CCTV survey before and after building.

The manhole needs to remain outside the building but it can also be moved if necessary.

The builder has to adhere to certain rules when building over and it will be supervised by building control. The water company will issue a final certificate at the end.

If you google 'buildover agreement' and the name of the local water provider, you should find their rules etc.

Rebuild on that footprint I can understand. An extension would be more than a bit odd, but I'll take it that the relevant professionals haven't been consulted.

Sillychuckie

Doozergirl wrote: »

if the sewer is shared with your neighbours - which looks to be the case.

Yes. Ours would be the last property it passes under in order to join the street sewer, so it carries the waste of a large number of properties (a pleasant thought!).

Doozergirl wrote: »

The manhole needs to remain outside the building but it can also be moved if necessary.

I don't imagine we would build beyond that, so that is OK.

It sounds like it isn't a show stopper - thanks. I have looked through the water company docs and read about their rules and use of pea shingle etc. I just like to hear another human say the same.

Doozergirl wrote: »

Rebuild on that footprint I can understand. An extension would be more than a bit odd, but I'll take it that the relevant professionals haven't been consulted.

You are right. We would almost certainly rebuild, but I feel it is too soon to involve professionals, because we plan to let out the property for a few years before getting started (so we can get rent in whilst waiting for all the permissions etc).

One concern though is that the water company states they would reject any planning permission to build over public sewers for "new build detached properties". The sewer would have to be diverted.
I guess that would include us, and we may have to divert along the right edge (as close to the electrical substation as underground wires/cables allow).

I suspect the architect will be earning his money on this one.

Thanks.
SC

[Deleted User]

My neighbours applied to build an extension over the sewer. They were granted permission on condition that the water board could demolish the extension any time they needed access, and then leave them to rebuild it at their own expense.

Doozergirl

jack_pott wrote: »

My neighbours applied to build an extension over the sewer. They were granted permission on condition that the water board could demolish the extension any time they needed access, and then leave them to rebuild it at their own expense.

That is not how buildover agreements work and I don't believe it for a second.

As you can imagine, if that were truly the case, the house would be completely unsaleable. Try raising a mortgage against that!

victor2

We built an extension over a shared sewer. Had to get a camera survey before and after the build to get the water authority's approval and acceptance. Foundations had to go underneath the sewer pipe and it was necessary to box around it so that the concrete didn't contact the sewer pipe.

tonyh66

If you were to divert it I would go left edge, then across the front with an additional MH at front of house.

Sillychuckie

Ok, thanks all.

jack_pott wrote: »

My neighbours ... were granted permission on condition that the water board could demolish the extension any time.

My 'extension' will actually be 'half of my new-build house and include 2 storeys, so I don't like the sound of that. I too don't really believe it (as Doozergirl suggested).

Sorry for any confusion using the word 'extension', its going to be far more significant than that.

Thanks Victor2, you give me further assurance that I can proceed with my purchase knowing that it isn't a show stopper and I can at least plan the ins and outs over the coming years.

tonyh66 wrote: »

If you were to divert it I would go left edge, then across the front with an additional MH at front of house

Thanks - yes, you could be right. I only suggested around the right side because it could flow through the existing man hole, but, if the works are going to be extensive enough to divert, it might make more sense to move (and/or create new) man hole(s).

Cheers all - appreciate everyone's contribution.
SC

[Deleted User]

Doozergirl wrote: »

if that were truly the case, the house would be completely unsaleable. Try raising a mortgage against that!

Which is why they decided to move house instead of building the extension, and why the new owners built an extension that isn't over the sewer.

SailorSam

I don't suppose modern houses are like this, mine is about 60yrs old and all the waste and water goes into one drain, even next doors comes into my back garden to join the drain. And we built over it when building the garage.

Doozergirl

SailorSam wrote: »

I don't suppose modern houses are like this, mine is about 60yrs old and all the waste and water goes into one drain, even next doors comes into my back garden to join the drain. And we built over it when building the garage.

It's a newish law from 2011. It will apply to your house now and any new work as you have shared drains.

Water companies are obliged to adopt all shared drains. It makes them responsible for issues, so they need to check that any new work by homeowners is compliant with keeping the drains intact.