Vertical dpc

25 Jun 2013
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United Kingdom
Hi, I am currently building an extension at home. My building control officer has asked for vertical dpc chased right through external brickwork where my new cavity wall meets the house. I am now wondering what to do where my wall meets my single skin brick garage. Any ideas what will be required?
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Thanks for your response. Had thought that just wanted another opinion. My bco seems a bit of a jobs worth so need to make sure I don't give him any reason to complain.
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BCO? building inspector? Never argue with them! I have seen builders argue with them and things go from bad to worst, if you got a small problem ask them for their advice, it works a treat, I've had one guy explaining the different grading for timbers, C16, C24 what was that all about? another giving me a green light for footings about a foot deep, (solid rock) if you let them think they are important due to their vastly superior knowledge, not only will they assist you, you will see a lot less of them, as in; when you get to the wall plate give the office a call.
Resistance to the passage of moisture requirement only applies to habitable rooms
I suppose this inspector is expecting the OP to hire a 12" grinder to cut a vertical slot in the existing brickwork, and insert the dpc into that.
Complete and utter waste of time for no advantage whatsoever.
Before you go cutting anything ask him exactly what he wants you to do, it may just be a case of affixing it to the wall with a starter kit.
Unfortunately I already had dpc rolled up the wall 300mm wide and wall starter kit all bolted up ready to build when he came to look at drain runs and he told me he wouldn't accept that and I had got to chase right through brickwork, I questioned this as weakening the structure and the wall we building against gets cut through flush with internal block work. Effectively once brickwork is cut for dpc the internal block work is tied in to a piece of brickwork approx 6 inches wide once wall cut through to make new opening also the brickwork piece that the bricks tie into is only about 10 inches wide to the corner of the house. He claimed loads of strength left there and tied onto starter kits. A mate did his extension only a few months ago and his building inspector said 300mm dpc up wall and fix starter kits was perfectly acceptable, different area though.
Building inspectors often know little about purely structural matters.
Yes, cutting through the skin weakens it for no gain at all. To say 'there's loads of strength left there' is not acceptable. Could he quantify it?

Dampness won't be an issue here; he's just looking at it from a theoretical aspect rather than being practical.

You really need to be polite but firm on this one. If it's a garage, damp is not strictly a problem. I certainly wouldn't compromise the stability of my own house on the say-so of some dim-wit inspector.
Can you post a plan sketch showing the wall connection arrangement and what is internal, external? It will save a lot of time and you'll probably get a response/solution to give to the BCO
I agree with the BCO. You should cut the existing wall at the back of the new external wall, remove that bit of wall completely, and take the new blockwork up to the existing internal blockwork and bond it in. This let's the cavity be continuous

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