Advice on Extension Near Sewer

Toothy1911 · 20 Feb 2021 at 15:17

Planning my first extension and need some advice to help me move forwards.

Going to build a single storey room to the rear/side of my house. But the intended foundations would come within 3 meters of the sewer. It looks like the sewer will be deep enough not to pass through foundations, which will make construction simpler.

However, I'm a unsure what planning / building control I will need. If the sewer wasn't there, I would just need a building notice. All other aspects of the build fall well within that category.
But because of the sewer it seems like I need to submit full plans instead. Which will require me getting an architect on board (unless I try drawing them up myself) and a lot longer process (2 months wait, rather than 2 days). Additional to this, I need to gain approval from my water company. Which I can do as a self certified form.

Is it possible to get the water company to approve the work, and then submit a simple building notice application? Or do I have to submit full plans and water company approval too.

Any help or experience welcome. I guess I'm trying to avoid the most costly and lengthy outcome. For a relatively small and simple build.

Myth · 20 Feb 2021 at 21:00

I have just done it, I went on Severn Trent water website and did a self assessment. Was around £60 and goes towards your building sign off.

The self assessment asks you questions or there is another one where they come out. https://www.stwater.co.uk/content/d...protection/Self_Cert_Application_Form_Web.pdf

Essentially we started found it during the footings and then sent off for it. It was really easy and no major concern.

Toothy1911 · 20 Feb 2021 at 23:13

Myth said:
I have just done it, I went on Severn Trent water website and did a self assessment. Was around £60 and goes towards your building sign off.

The self assessment asks you questions or there is another one where they come out. https://www.stwater.co.uk/content/d...protection/Self_Cert_Application_Form_Web.pdf

Essentially we started found it during the footings and then sent off for it. It was really easy and no major concern.

Thanks. Were you building with a building notice, or did you have full plans?
I've sent Severn Trent and email asking them for guidance.

Myth · 22 Feb 2021 at 22:05

Toothy1911 said:
Thanks. Were you building with a building notice, or did you have full plans?
I've sent Severn Trent and email asking them for guidance.

We have full plans however Severn Trent did not ask for any of this.
I filled the form in sent it over in an email and then paid. A week later it was signed off and I sent the form over to my building inspector.

Hope this helps.

Toothy1911 · 22 Feb 2021 at 22:33

Spoke to my council today, and they have said in writing I just need to apply for a building notice. They say there are no sewers running through my property according to the Severn Trent map.
I don't know what they class as a sewer, but there is definitely a waste pipe with large manhole running through the garden. Maybe it's not classed as public and I can do what I like near to it.
Little confused what to do. Whether I still need a build near / over from ST

mickyflinn · 22 Feb 2021 at 23:04

Contact seven trent.

Toothy1911 · 23 Feb 2021 at 07:19

mickyflinn said:
Contact seven trent.

Yep. I will respond to them today I guess, telling them what my council says.

Toothy1911 · 23 Feb 2021 at 09:54

Severn Trent have told me that probably would have been a shared sewer originally, which were all converted to public (as of 2011). And because of that, not all show up on maps.
So seems like my council doesn't have the correct info, and may be misguiding me.

No idea why they make things so tricky. I suppose most people would just build and ignore it! Trying to do the right thing is always hard work

tom_nieto · 23 Feb 2021 at 10:40

We had to have a CCTV drain survey before and after construction and dig foundations 3m deep (single storey extension) so that no weight was sitting on the pipe work. We didn’t have to build over the pipe, just next to it (~1m away). It threw everything into chaos and we were poorly advised by our builders as to what to do. We’re in a Severn Trent area.

Be careful and don’t rush. Speak to the water board and get everything sorted in writing first. Architect’s drawings will often help if you’ve got to have fancy footings.

Puzzled · 23 Feb 2021 at 12:01

It depends on if the sewer is just for your property or if sewage from other houses passes through it. If it's the latter then it becomes the responsibility of Severn Trent and you will need their permission to build over it.

https://www.stwater.co.uk/content/d..._or_close_to_a_public_sewer_guidance_faqs.pdf

It scuppered our plans as we have manhole covers and the sewer connects to neighbouring properties so added too much hassle. The builder didn't seem to know about the change in ownership though and advised us to just build over them and put manhole covers inside. That could have been a very expensive risk to take as the water company can demand that you take it down and put things right.

Toothy1911 · 23 Feb 2021 at 12:13

tom_nieto said:
We had to have a CCTV drain survey before and after construction and dig foundations 3m deep (single storey extension) so that no weight was sitting on the pipe work. We didn’t have to build over the pipe, just next to it (~1m away). It threw everything into chaos and we were poorly advised by our builders as to what to do. We’re in a Severn Trent area.

Be careful and don’t rush. Speak to the water board and get everything sorted in writing first. Architect’s drawings will often help if you’ve got to have fancy footings.

Puzzled said:
It depends on if the sewer is just for your property or if sewage from other houses passes through it. If it's the latter then it becomes the responsibility of Severn Trent and you will need their permission to build over it.

https://www.stwater.co.uk/content/d..._or_close_to_a_public_sewer_guidance_faqs.pdf

It scuppered our plans as we have manhole covers and the sewer connects to neighbouring properties so added too much hassle. The builder didn't seem to know about the change in ownership though and advised us to just build over them and put manhole covers inside. That could have been a very expensive risk to take as the water company can demand that you take it down and put things right.

Thanks both. I'm a little concerned I will have to go to do really deep foundations or not be able to build at all. Time will tell I guess.
I know I will need to get a self cert or full build over with Severn Trent, I'm all good with that. At this stage I'm still unsure if I need full plans with my council. I'm betting my council will change their mind when I speak to them again. Hoping they say a building notice will be acceptable still.

ZombieFan · 23 Feb 2021 at 13:07

It will depend on your water company and/or your local building control (and probably what day of the week you speak to them!

)

We've just completed an extension which is over a mains sewer pipe. I sent Wessex Water the same plans which we had for planning permission, but sent them *before* submitting for planning (on the basis that if Wessex Water were not going to let us build, there's no point in applying for planning).

Wessex Water wanted more detailed plans of how the walls would be supported over the pipe (foundation depth, lintel dimensions etc.). I was able to put these plans together myself with help from a builder friend, so you may need an architect to do this if the water company requires it.

They then sent around a man with a robot thing to take a look at the condition of the pipe, and we ended up with a letter confirming that they were happy for us to build.

After we got planning, we submitted all the info we got from Wessex Water to building control. I was unsure about if we needed full plans or could use a building notice so I phoned them up and explained that the water company were happy with our plans. On that basis, they were happy with just a building notice.

Our builders were also happy with the building notice (they were experienced local builders with a good history/reputation). The building inspector didn't have any issues with it when he was checking out the foundations.

Toothy1911 · 23 Feb 2021 at 15:19

Council have confirmed that because there is nothing on the map, only a building notice is required. Great news.
Will proceed with that and whatever Severn Trent applications I need.
Some great info coming from you guys so far. Thank you!