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How can I bring a solid 9 inch wall up to building regs?

Postby Converter » Tue Jan 22, 2008 10:31 pm

I am planning to convert my part integral garage to living accomodation. I have the design underway and will be applying for building regs soon. The front 8ft of the garage protrudes form the front of the house. The walls at this point are solid 9inch walls with no cavity.

Is there any way that I can "dry line" these without including a cavity so as to keep as much room in the already rather narrow garage as possible. Obviously any suggested solution must comply with the building regs.

Can anyone help.
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Postby arbco » Thu Jan 24, 2008 7:33 pm

In the 9 inch section you could line with celotex or kingspan insulation and not have a cavity prior to the plasterboard. Off the top of my head 70mm would be OK but check with the manufacturer.
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Postby bd3cc » Wed Jan 30, 2008 9:37 pm

I think you could probably, "black the interior walls and then either render them will a sand cement mix with waterproofer, or even just plaster them with bonding and a skim coat.
As in many cases, tell BC that you are doing the work, pay the fee and ask their inspector how he requires it to be done.
There is a common misconception that you are no longer able to touch electrics, windows and many other things in your own property.
In almost all cases, if you notify Building Control of the works and pay the appropriate inspection fee, provided that they are satisfied with the work,
no matter who has carried it out, it will be signed off, and you will have no problems when selling the property.
If this were not the case, DIY sheds, Wickes etc would no longer be able to sell double glazed windows for DIYers.
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Postby LCL » Mon Feb 04, 2008 6:47 pm


We have designed many similar such projects. The following has received building regs approval within the last week, so should be OK. 3 Coat synthapruf the wall, 20mm render (important if going over a liquid based water proofer), erect metal studs at 400mm centers, fill the void between the studs with Celotex GA3000 insulation and finish with 12.5mm plasterboard and skim.

Some variations include: 1. Put a vapour barrier ont he warm side of the insulation, and / or a further 12mm thick Celotex lining insulation over the framework and behind the plasterboard.

One very important point is NOT to treat the external surfaces of the wall with waterproofing or cement based render etc as the wall will need to breath owing to the fact that the water proofing has been installed on the internal face. If you need to re-point the wall, use a lime : sand mortar mix, do not use cement at all, likewise if you really want to rneder, use a lime : sand render mix to help the wall to breath.

Hope this helps.

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Postby arbco » Sat Feb 09, 2008 9:11 pm

If the whole wall is 225mm then the suggestion from LCL may not apply, otherwise this is a pretty good spec for upgrading an existing 102mm wall.

Some BCO's request a cavity is maintained prior to the new 100mm stud wall (but have flexibility on the width 25mm-50mm). The stud should be constructed off a DPC on a brick/block with a 225mm clear cavity maintained below the lowest DPC as Part C .
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