Building over a drain

Gewens

I am after some advice from the knowledgeable people out there is MSE land.

We would like to build a 4m by 2.4m extension to the rear of our terraced house. Our neighbour on one side done this 16 years ago but since then I appreciate that regulations have changed.

We currently have a man hole in the garden which is in the area of the proposed extension, as do all the other gardens.

We have had 2 architects round to quote for the drawing side. The first said we could build over the drain, the bottom would need to be changed to a full pipe within the man hole and then it could be built over using lintels at either side of the new building.

The second has turned up today, said we can't build over it and left.

We now have 2 very conflicting views! Does anyone have experience of this and can advise if we can or can't do it. Obviously we will be disappointed if we can't, but if that's the rules then that's fine.

Our sewage service is provided by Southern Water.

Really appreciate you taking the time to read this.


https://ibb.co/Qcm1f5G

https://ibb.co/MR72yff

a.turner

If it's a shared drain you'll need a buildover agreement from the water company.

Gewens

a.turner wrote: »

If it's a shared drain you'll need a buildover agreement from the water company.

Yes we were told that by the first guy, which is fine. It was the second guy just turning around and saying no that supprised us.

Doozergirl

You cannot have an inspection chamber inside the property even with a build over agreement.

Where you have junctions in your drainage, you should have an inspection chamber. On the whole, you can't bury junctions, you need to be able to rod every part of the system to clear a blockage.

You have to find a solution that moves the inspection chamber and satisfies building control. You need to know all your drainage routes around the property in order to work out how to do it.

If you are in a terrace, sharing the sewer with others and want to build full width, then your options will be a bit more limited.

Someone in a semi might be able to move theirs to the side but keep the new chamber on the same drainage run. With a terrace, it might mean diverting the whole sewer around the house. If your neighbour has already built over their inspection chamber then you can't exactly dig that up to divert the route and probably still need one chamber on your side on the existing run in order to be able to divert it. That would scupper a full width extension.

Your first architect hasn't provided a solution to the inspection chamber issue - it looks like you have three routes into that pipe from the house/somewhere and you cannot just replace waht you have with a buried pipe with junctions off it.

Southern Water will provide an advice document on their website.

Davesnave

Gewens wrote: »

Yes we were told that by the first guy, which is fine. It was the second guy just turning around and saying no that supprised us.

As Doozergirl says, it looks as if he's right, so far as a full width extension is concerned.


If that's your neighbour's wall on the left, there isn't scope for a simple, smooth diversion, so it may come down to a re-design, leaving access to the chamber outdoors.


It's whether that can be done in a way that's acceptable to you which must be decided now. If that architect's communication skills were as bad as they seem, I'd not use him, but the other one should have made the restriction you face clear too.

keith969

Doozergirl wrote: »

You cannot have an inspection chamber inside the property even with a build over agreement.

Really? I have one in my garage, which was probably put there when the house was extended some years ago. Or have building regs changed?

Heedtheadvice

....an example of the "architects" being bad at their jobs (ref. my other post on Architect vs QS vs PM in anothef thread) where a lot revolves around individuals competence. In this case it seems (unsurprisingly being the Doozy one ) a resident poster on here 'only' a builder knows a lot better and can explain better than the professionals.


There have been inspection chambers historically mace inside buildings. That does not make it right for good reasons. Consider a blockage and the level rising higher than the cover......


OP why not go independant of the architects initally and ask building control? (Assuming you can get a response these days!) There have been a couple of very sensible posts above but we cannot see all the site detail and whatever anyone tells you Building Standards as interpreted by your local building control need to be complied with. With their opinion (prior to planning application (a separate issue) and building warrant application could save you a lot of anguish, time and money. Do not mistakenly think next door's extension is anything to go by.

frozen_wastes

My sister had an extension built, but very early on in the build they uncovered an underground drain. The water company said that the drain would have to be diverted to accommodate their project, so they had to fork out an extra £20k for the drain diversion. It was a main drain under their land, but as such the drain was the water companys property, and it had to be moved with their consent to their standards.

Not cheap, but it was either £20k, or project abandonment. They decided to commission the drain diversion and save the project.

Davesnave

keith969 wrote: »

Really? I have one in my garage, which was probably put there when the house was extended some years ago. Or have building regs changed?

Yes, it used to be permissible.