Sewer pipe and extension footings

[TheLeester]

I am planning an extension but wonder what my options are regarding the sewer pipe that run to the parrallel to back of the property about 2.5m away.

How close to the pipe can I dig the footings ?

If I decide to build past the pipe, the manhole cover access will be within the extension. I don't fancy the prospect of a blocked sewer flooding the property. Is it expensive/difficult to have the access shaft resited so that it is outside the property ?

 

[GlynL]

You should get in contact with Building Control at your Council.

They will be able to help you on dealing with pipes and manholes at your proposed site.

It is a legal requirement that you make an application for Building Regulations before carrying out building works. They are here for exactly the type of problem you may have and can certainly help with a little pre-application advice.

 

[amatureleccy]

Regulations for building over sewer and the siting of manhole's are particular to each local water authority.

In Thames Water's case, you cannot site a manhole internally - it must be external. You can build your footings over a pipe but you will require particualr lintles. Building a new manhole should come in at around £450 (depends on your area).

 

[mildmanneredjanitor]

We had a similar situation to this ourselves, our people wanted to route the pipework around the extension as it had to be made accessable. Also the pipework served other properties upstream, maybe this was why???

Personally, I would have thought that adding two sharp bends to a run of waste pipe would cause problems and the better solution would have been to have lintels over the pipework where the walls were built. But I'm not the expert I suppose!

 

[TheLeester]

I am indeed in the Thames Water area. Apparently you need 'Build over agreement' from them if you plan to build within 3m of a public sewer, which they tell me ours is.

They did explain to me the concept of using lintels to bridge the sewer. I think I would prefer to re-site the thing. If the sewer were to fracture and start flooding soil around the footings, there would be a danger of heave I would have thought. I wouldnt even begin to imagine the cost of putting something like that right.

 

[amatureleccy]

Buildover agreement costs £350.

From what I remember, so long as you abide by the specification given to you by Thames Water, the agreement should insure you against the risk you mention. Although the worrier in me tells me that there will be some small print get out clause for Thames Water.

If you find out whether the agreement coveres you, I would be grateful of you would post back with any info.

My situation was also similar in having other properties up-stream using the same sewer. The problem with re-routing it is that there have to access points in straight lines for rodding and blockage clearance - corners obstruct this.