Building Regulation Plans and Architect

[PenfoldA]

Hi All,

I'm new to all this (both the forum and the scary work of DIY). So please bear with me and apologies for the lengthy post thats about to follow.

I'll give you a little background on our plans thus far...

So we are planning on having a single storey extension built to improve the layout/ size of out teeny tiny kitchen and bathroom. We have contacted the local planning dept who requested a 'sketch' of our proposed extension and have agreed in writing that it is within permissible development. (one tick in the box at least) we're talking 3m (in line with the existing width of the property) x 2.8m.

On discussing with Building Control and having a dig in the garden, we discovered that the sewer pipe runs 1.1 metres away in line with our property. So obviously we are required to submit building regulation plans as what we intend to do is within 3m of the sewer.

Really I'm looking for a little advice from all your wonderful experience, we have contacted Southern Water who verbally agreed that building over the sewer would not be a problem and this would be agreed fully when Building control have received our application and notify them??!

I have just had a look on their website and discovered this..
http://www.southernwater.co.uk/pdf/...uilders/sewer-connections/BuildOverNotes.pdf.

Stating that they are unlikely to approve building over the sewer if we can divert instead. Now am I being a complete plank and thinking this would be the case if perhaps the extension covered the sewer pipe right across our land.

What I'm hoping is that as there will be a meter or so to the right of our property still that a manhole could be moved to there to provide access? (Luckily we've never had any problems as there isnt even an existing manhole)

So that was abit of a sideline while I was here, what I actually wanted to check out was. We have spoken with an architect and agreed a fee (much to the sadness of our bank account) to draw up plans for the purpose of building regs. We have spoken with building control who have agreed that our proposal to use a 'catnic' rather than an RSJ was fine with them, so that we could avoid the costs of a structural engineer.
Our architect has just got back to me today to say that we would need to appoint a structural engineer to calculate the design for the drainage and foundations????!!! Am I totally wrong that I thought that this was kind of what architect's did...design? We have discussed with him that we are using standard construction to and (obviously) the idea is for it to meet building regs, shouldn't he know these? Or am I totally missing something.

He did note when I questioned that this doesn't have to be done by a SE but it would be our responsibility to ensure it was correct.

Apologies if I'm just being a little dim, as I say we're novices at this. I must add that (now worryingly) we intend on doing all the manual work we can to try and keep costs down, my father is a builder/plumber by trade. But lives 60miles away and is always super busy so it is tricky to get hold of him, (he was however, under the impression an architect would do this though)

Thanks in advance

 

[noseall]

First of all (apart from typing such a long post) how deep is the drain?

Do you know how deep the existing house foundations are and what type of soil conditions exist below ground?

Your architect should be familiar with your area or at least you should pick one that is. Because you can bet that B.C. WILL be familiar and will expect the foundation spec' to reflect ground conditions.

Anyhoo, back to the drain.

We did a job last winter and were surprised to find a 6" main sewer running across the site. I decided to carry on with the foundation dig, shutter each side of the sewer pipe (both times it crossed the trench) and pour the concrete.
This meant that the pipe remained unmolested.

I spoke with the water company (by phone) and informed them that I intended renewing the pipe in plastic where it passed under the building and that I would install an inspection chamber at one end. I explained that neither the concrete or the building would be influencing the lie of the drain as it was all shuttered and would be lintelled over.

They were ecstatic and would inspect with cameras once things were built.

Bear in mind though that the drain in question was not prohibitively deep, i.e it was only a metre or so at its deepest.
I also took loads of photos to boot.

 

[tony1851]

As above.
If you've got space for an inspection chamber, that will help.
When in close proximity to a drain, the foundation should be taken down to at least the invert level of the drain (ie the level of the bottom of the pipe).
The width of the foundation would be dictated by ground conditions, but for a simple extension to an old house, foundations are within the competence of an architect - or should be!.

 

[simonjay]

As above.
If you've got space for an inspection chamber, that will help.
When in close proximity to a drain, the foundation should be taken down to at least the invert level of the drain (ie the level of the bottom of the pipe).
The width of the foundation would be dictated by ground conditions, but for a simple extension to an old house, foundations are within the competence of an architect - or should be!.

When I built about 1.5 metres from a 2 metre deep 12" public sewer, the water company were fine with the foundations being just lower than the load line (45 degrees upward from invert of sewer). I think if within 1 metre I would have had to go to invert depth however.