Building Control Confusion

Hi,

Been searching the internet based on my current problem, and think I am now overthinking it and tying myself up in a knot!

OK, current situation: Couple of years ago moved into a 30's house with prebuilt extension on the back (Flat Roof) - We are planning on upgrading the extension with:

• New BiFolds to replace patio doors - This will consist of a new A frame going around the bi-folds as I don't know how deep the foundations are, along with a steel (calculated by SE) going in above the doors
• New warm roof - Extension was built in the 60's (I believe) so roof needs renewing, so will convert it into a warm roof with some skylights / velux'
• Celotex / Ecotherm type insulation - The extension on 2.5 of its sides are now internal walls, however the external walls are single skin (4 inch) block so my plan is to insulate the hell outta these in order to bring it up to standards

All OK so far I think, not for much longer! Firstly, there is a drain access (double sealed) underneath the floor in the utility room. I found this recently when my toilet wasn't draining quickly, and the water board had to come out and rod it - Not the end of the world as I know the water board used to allow double sealed units, so its not that its not compliant. The other issue is when we bought the house there was no record of BC sign-off for the extension, but were advised this could be due to the age, and the SE confirmed it is structurally sound.

Last bit I promise. I effectively want to bring the extension to modern standards, whilst also removing part of the original house back wall (along wil a full chimney stack) to make it open plan - This is where I have tied myself up in knots:

• Do I need to move the waste access cover to outside the house? I understand that any work within a certain distance needs a BO agreement and moving? I am mainly thinking of the a-frame and excavation works as its very close (1.5m) to the access cover) I am at the top end of the road / pipe, and my house if the first to enter the shared pipe - does that make a difference? If i were to move it, it would have to go under an existing wall and foundations?
• 4 Inch external wall - This is a big concern but the SE seems to think i can put 150mm Celotex or similar and vapor barrier and it should be OK?
• Removal of existing wall - Obviously will get BC sign-off for this, but how does it work with the existing structure not having any trace of it? Can I get the old extension signed off too? It wont be complaint with BR now as I very much doubt the foundations are 1m.

The whole place will be re-wired, plumbing / gas re-done, Celotex installed, warm roof,...my main issue is the existing structure and waste cover,...

What you reckon? Proceed, or tear it down and start again and move the drain?

Sorry for the long post!

Ta muchly

Hi, I can't answer some of your questions, but part of your situation is similar to mine.

We've just knocked through into an extension that we inherited on our 1930s semi when we moved in. It too had no BC sign off when it was built, but it was so long ago we were assured that building control wouldn't be bothered, and the work was to a high standard.

I was a bit nervous when the inspector came for 1st visit, but all I said was "it's just the knock through, not the extension" and he was happy.

I certainly wouldn't go trying to get the extension certified. Just make the changes you describe, and I'm sure BCO will be happy. They are not that unreasonable.

You will prob need a SAPS test for the whole house -which wont be a problem as you are improving the insulation, any improvements to the house count as well.

The drain can stay.

You would only really need to apply for permission for the new works. Building control won't be interested in the existing unless its unsafe.

You will prob need a SAPS test for the whole house

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Based on my experience I doubt it. Small existing extension opened out to full width with new knock-through. BC were only interested in the new bit, and even then not much.

Is the structural engineer obtaining building regs approval for you

Thanks for the replies everyone, didn’t expect so many quick replies, so thank you all.

@Leofric No, SE not seeking approval as of yet, although recommended a private company that one if my friend has also used and recommended. The whole point with the SE initially was to see if it was possible what we want to do, so I have the best intentions to do it right, just that the existing structure strikes me with a little concern.

I do fear it was a conservatory at one point, which was changed for a flat roof many years ago (which would potentially explain the single 4 inch skin). We plan to be here for many years and the kids will grow up here so can’t see us selling it for another 15-20 years.

Regardless of whether the building is compliant or not, I want to do it right so I think my first plan will be to dig a pilot hole to see how deep the foundations are, then, I can DIY underpin if necessary every metre or so (as this’ll be the least intrusive / disruptive) and then also add a second skin to that end wall to improve load bearing, as well as the new roof and wall insulation.

Along with the wiring, plumbing and all the steel work being signed off, the only 2 points of concern is that fact that the floor may not be insulated and the sewer access but I assume as it used to be ok, there are millions of homes that have it in their house and that’s where the double seal comes in?

Is the likelihood of issues reduce as I’m at the top / first in the sewer line? We don’t live on a hill.

I’m a massive over thinker, and I know it’s way in the future but I don’t want the headache of someone trying to knock 20k off the sale of the house as this certificate would be missing.

Thanks everyone.

peregrine_85 said:

4 Inch external wall - This is a big concern but the SE seems to think i can put 150mm Celotex or similar and vapor barrier and it should be OK?

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When somebody tells you something should be OK what they really mean is somebody else should confirm it actually will be OK .
Difficult to say without seeing the place but it might be better to demolish the extension and build a new extension to get exactly what you want to comply with current bldg. regs. This is where an architectural designer would come in to deal with the whole scheme of alterations and extension with structural engineer's input as required.

A 4-inch brick wall with insulation on the inside would not comply with the recommendation in Approved Doc. C for resistance to rain penetration, and would be flagged up by the inspector.

Membrane before the insulation.

garage conversions with single skin are possible.......