# Building extension of public sewer



## richtung (Apr 14, 2008)

*Building extension over public sewer*

Hi Folks,

just near the end of the purchasing process on our next house. The property is on a large corner plot and we intend to extend the property at some point in the future.

The drainage search has come back which shows a sewer running through the boundaries of the property:










The property is number 2 and we intended to extend the property to the right (pretty much over the sewer). My solicitor said we would need to apply for a build over agreement with United Utilities.
From a structural point of view, I assume there wouldn't be an issue with building over the sewer (once the appropriate consents / approvals have been received)?

Thanks in advance

Rich


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## Clancy (Jul 21, 2013)

You sure the sewer is there and not under the road ? Do not take maps of services as Gospel, they tend to show you what postcode a service is in and that's about as good as they get :lol: unusual for the main sewer to run through a plot, or is it just a connecting pipe ? 

Just a case of applying for permission, you are at their mercy tgough

The architect or engineer whoever does your plans will most likely need to do calcs to check the load doesnt cause excess pressure at the sewer, which will be stipulated by them when you apply for permission, may alter the design of your house but unlikely that a residential dwelling is ever going to put enough load through the soil to bother the main sewer unless it's very high at that point


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## richtung (Apr 14, 2008)

Thanks for your reply.

I hadn't considered the possibility of the sewer pipe running just outside the boundary and the map was a "rough" guide.

In any case, i would have to assume it is accurate though and take it into consideration when getting the plans drawn up.

Cheers

Rich


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## turbosnoop (Apr 14, 2015)

I was digging some ground up at the side of my house last year, as I was laying slabs. About 2 inches below ground I found a manhole. Some idiot covered it up. On lifting it, it looks like it serves our house plus 2 houses to the left and 3 to the right. Or possibly more, hard to say. Just glad noone has blocked it in the six years we've been here. Good luck with the move , one day too I would like to add an extension over the sewer too. Bit of a pain knowing its there but I guess that's what happens when you buy a house with a nice bit of space to the side which noone else has


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## Bero (Mar 9, 2008)

richtung said:


> Thanks for your reply.
> 
> I hadn't considered the possibility of the sewer pipe running just outside the boundary and the map was a "rough" guide.
> 
> ...


I think you're doing the work back to front.

I would verify where the pipe actually is first (should be very cheap) then get the plans drawn up (comparability expensive).


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## Clancy (Jul 21, 2013)

Bero said:


> I think you're doing the work back to front.
> 
> I would verify where the pipe actually is first (should be very cheap) then get the plans drawn up (comparability expensive).


Yeah exactly this, find the actual location of the pipe first

Will completely change where you go after that


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## richtung (Apr 14, 2008)

Thanks for the advice guys.

In order to verify where the pipe is, would it be the water board (in my case United Utilities) or drainage company to come out to look for the pipe?
I'm assuming it would be relatively deep under ground?

Rich


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## fatdazza (Dec 29, 2010)

The filled circles on the line of the sewer are generally indicate manholes. If you can verify the position of these then this should initially help to verify the line of the sewer.

The exact location should always be identified by trial holes.

Contact United Utilities and they should be able to help with the size and depth, and will advise on their requirements for a build over.

As previous poster has said, the maps are just a guide and actual locations can be a way off from that shown.


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## Bero (Mar 9, 2008)

richtung said:


> Thanks for the advice guys.
> 
> In order to verify where the pipe is, would it be the water board (in my case United Utilities) or drainage company to come out to look for the pipe?
> I'm assuming it would be relatively deep under ground?
> ...


Yes, give them a call and tell them your planning landscaping / making a pond / building an extension and concerned you might hit their services. I'm not sure if they will mark them for free or not. If you say services hopefully they will map your incoming water too.

If you're really confident you can positively identify the covers take a look on the road if you see them there.....and there is nothing else they could be.......

Edit - I see Fatdazza beat me to the idea of manhole spotting.


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## robertdon777 (Nov 3, 2005)

Pop into your local water authority and ask to see their plans. This is what I did and they have detailed maps of the main sewers/drainage but not on the property.

You will probably need a build over notice anyway because of other drains etc around the house.

All you need to do is have a CCTV survey done of drains before and after the build if you are doing a build over. Less than £150 all in and you will be covered if any future issues arise (they can't blame you)

The actual build over process is a fairly simple concrete bridge structure.


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## dholdi (Oct 1, 2008)

We built over a shared drain serving both ours and a neighbours properties which in effect makes it the water authority's responsibility ( in our case UU )
We wrote to them informing them of our intentions and our proposed method of protecting the drain.
They replied to the effect that as long as it was done with Building Reg's approval they were fine with it.


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## kh904 (Dec 18, 2006)

robertdon777 said:


> Pop into your local water authority and ask to see their plans. This is what I did and they have detailed maps of the main sewers/drainage but not on the property.
> 
> You will probably need a build over notice anyway because of other drains etc around the house.
> 
> ...


My parents are getting a rear extension done which builds over the manhole cover for the sewage. 
We had to fill in some paperwork (build over notice?) for Thames Water and some money was involved.
I'm not sure if anyone from Thames water will come and visit before and after the build.


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## robertdon777 (Nov 3, 2005)

kh904 said:


> My parents are getting a rear extension done which builds over the manhole cover for the sewage.
> We had to fill in some paperwork (build over notice?) for Thames Water and some money was involved.
> I'm not sure if anyone from Thames water will come and visit before and after the build.


They don't have to visit, usually the building inspector will come out to see the foundations/build over and pass it off.

They usually just need to know what you are doing and how close you are to any pipes and that the build over causes no damage. Obviously if you get all the details done before they shouldn't have any issues giving you the permission letter to build over. Sometimes they will insist on a DVD of the CCTV.

Some builds don't require CCTV, for example if you are First inline of a terraced street, if you cracked a pipe etc it wouldn't matter to your neighbours.


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## BavarianRob (Mar 28, 2010)

You need to consider the depth of the drain and the size of the pipe, this could affect the depth and therefore the cost of your foundations. First job as others have said is to get an accurate survey done, pipe size, depth, accurate location and confirmation as to the use of the pipe i.e foul, storm or combined sewer. Your water authority should be able to tell you most of this, but get the actual depths checked, the records are not always accurate! A decent builder will be able to dig the foundations around the pipe and protect it. Look for a builder with NHBC recommendations. They may also be able to survey the pipe for you and give you some options. You'll have to spend a bit to get the approvals as you'll need plans drawing up but it's do able.


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