Building an extension over existing drains

[Chris S]

This is probably spelled out in Building Regs., but, seeking a shortcut, ca n anyone give me the main issues relating to the following.

I am contemplating building a (two storey) extension on the side of the hou se as a rectangular add-on. To be viable this would mean that it would go o ver an existing run of straight sewer. (This is a sewer carrying neighbouri ng houses waste as well as mine). The sewer depth is about 1 metre. The fo otings of the outer wall of the extension would be parallel to and beyond t he sewer, and the side walls would both cross the sewer at right angles.

The new extension would contain toilets and a shower which I would hope to connect to the sewer internally. There are existing inspection/junction box es which would remain at either end of the extension.

Is building over a sewer allowable and likely to be uncomplicated in this s ituation?

The side wall footings would presumably need load spreading support going o ver the sewer pipe run. Would this need a detailed design, or are there sta ndard guidelines?

How close, laterally, can a new footing be to a sewer pipe. (Thinking of t he parallel wall)?

Is connecting extension drainage internally the best way?

Any other issues I should worry about? I'd appreciate thoughts from anyone with experience.

Thanks for your help.

[Andrew Mawson]

As I understand it the maintenance of a common sewer (ie one serving more than one dwelling) is the responsibility of the local water company. As such you would need their permission to build over it. Probably there is a way leave for it attached to your deeds, and if so it almost certainly precludes building over it.

Can the sewer not be re-routed? That would still need their permission but would be more satisfactory.

AWEM

[David.WE.Roberts]

First thing you need to check - as it is a shared drain has it been taken over by the local water authority?

If so you will need their permission and probably have to pay them a fee.

At my daughter's house they wanted about £400 to allow her to connect in a new soil pipe.

Cheers

Dave R

[Caecilius]

as a rectangular add-on. To be viable this would mean that it would go over an existing run of straight sewer.

I had this issue with a new build last year. I had to divert it, and it needed to me more than a certain distance away from the foundations (50 cm I think).

The water company (Thames water) were happy for me to divert, but wanted to inspect and do a CCTV check afterwards. They also said it had to be done with clay, not plastic.

It was a bit of hassle, but it all worked out OK in the end. The BCO and Thames water were both happy with the job.

[Tim Watts]

On Wednesday 13 March 2013 10:29 David.WE.Roberts wrote in uk.d-i-y:

They all have, but default, as of last autumn if memory serves.

[Chris S]

can anyone give me the main issues relating to the following.

ouse as a rectangular add-on. To be viable this would mean that it would go over an existing run of straight sewer. (This is a sewer carrying neighbou ring houses waste as well as mine). The sewer depth is about 1 metre. The footings of the outer wall of the extension would be parallel to and beyond the sewer, and the side walls would both cross the sewer at right angles.

o connect to the sewer internally. There are existing inspection/junction b oxes which would remain at either end of the extension.

over the sewer pipe run. Would this need a detailed design, or are there s tandard guidelines?

the parallel wall)?

e with experience.

Thanks, useful replies. The Deeds describe the sewer as a private sewer, wi th no mention of Water Authority, but presumably if some blanket regulation has been applied, deeds wouldn't necessarily be updated when the house cha nges hands (last done 10 years ago).

[John Williamson]

no mention of Water Authority, but presumably if some blanket regulation has been applied, deeds wouldn't necessarily be updated when the house changes hands (last done 10 years ago).

The change was made in October 2011, as detailed here:-

It was an automatic change, and I've certainly had no notification by the local water company about my shared drainage.

[Roger Mills]

anyone give me the main issues relating to the following.

as a rectangular add-on. To be viable this would mean that it would go over an existing run of straight sewer. (This is a sewer carrying neighbouring houses waste as well as mine). The sewer depth is about 1 metre. The footings of the outer wall of the extension would be parallel to and beyond the sewer, and the side walls would both cross the sewer at right angles.

connect to the sewer internally. There are existing inspection/junction boxes which would remain at either end of the extension.

the sewer pipe run. Would this need a detailed design, or are there standard guidelines?

parallel wall)?

with experience.

Your sewer will originally have been a private sewer, but private sewers serving more than one property have recently (2011?) been taken over by the water companies - so you will have to follow the same rules as you would if it were a public sewer.

You will have to get permission and pay a fee. You will have to follow the rules for building in a way which doesn't impose any load on the sewer - typically by excavating to below sewer level, and bridging over the sewer pipes. You will have to submit your plans for approval prior to the event, and get the actual work signed off by a Building Inspector. You are likely to have to pay for before and after CCTV surveys to prove that your building work hasn't damaged the sewer. Oh, and you'll probably be asked to perform a Risk Analysis! I had to do all of this when I built a detached garage over a public sewer.

I don't know who your water company is, but Severn Trent have produced a useful document which explains what you have to do in some detail. Go to

and then download the document in PDF format.

[Tim Watts]

On Wednesday 13 March 2013 19:39 Chris S wrote in uk.d-i-y:

Here, read this:

You should find a statement and further expanation on your foul water company's website...

[Jonathan]

house as a rectangular add-on. To be viable this would mean that it would g o over an existing run of straight sewer.

We put in a new one to bring waste from the back to the front. It goes through the house and we had lintels put in the walls over it. Building regs were happy with it.

Jonathan

[Hugo Nebula]

anyone give me the main issues relating to the following.

as a rectangular add-on. To be viable this would mean that it would go over an existing run of straight sewer. (This is a sewer carrying neighbouring houses waste as well as mine). The sewer depth is about 1 metre. The footings of the outer wall of the extension would be parallel to and beyond the sewer, and the side walls would both cross the sewer at right angles.

connect to the sewer internally. There are existing inspection/junction boxes which would remain at either end of the extension.

the sewer pipe run. Would this need a detailed design, or are there standard guidelines?

parallel wall)?

experience.

Perfectly normal, and something a BCO sees on about 50% of extensions in urban areas.

Normal procedure is to excavate for the foundations below the sewer/drain, and for about a metre either side. Depending on the ground conditions (& local custom & practice), the concrete would be stopped either side of the drain, or carried underneath. The concrete & the wall above would be clear of the pipe for a minimum of 50mm around it, and the hole where it passes through the wall sealed with fibreboard (or more often than not, wrapped with Rockwool). The wall would be built above off normal concrete lintels.

I would advise any new connections to be external to the building. If they are internal you would need either an inspection chamber with a double-sealed screw down cover inside the building (not pretty), or, if the connection is a straight T or Y off the main run, a rodding eye on the stub or vent stack. Imagine what would happen if this branch blocked, and how you would rod or jet it clean (i.e., 'Dynorod' bringing a sh1tty pipe through the house).

Since a few years ago, all post 1937 shared drains are now the responsibility of your local utility company. In my area (NWEng), UU have delegated the smaller building over agreements to the relevant Local Authority Building Control section (IIRC, for built over lengths of

[Chris S]

can anyone give me the main issues relating to the following.

ouse as a rectangular add-on. To be viable this would mean that it would go over an existing run of straight sewer. (This is a sewer carrying neighbou ring houses waste as well as mine). The sewer depth is about 1 metre. The footings of the outer wall of the extension would be parallel to and beyond the sewer, and the side walls would both cross the sewer at right angles.

o connect to the sewer internally. There are existing inspection/junction b oxes which would remain at either end of the extension.

over the sewer pipe run. Would this need a detailed design, or are there s tandard guidelines?

the parallel wall)?

e with experience.

Thanks. Useful answer.

[armouredsmiler0]

I have been talking to Thames Water and it would seems that they cannot 'en force'/not illegal that you inform them/apply to build over as my neighbour is building over a public sewer without informing them. What will happen i f there is a problem with the sewer and it found to be the build then they will not pay the repair but will charge the person responsible. Also they w ill have to lie on there sellers form if they ever sell.