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Message started by Arrow on Dec 12th, 2018, 9:40pm

Title: double stud wall
Post by Arrow on Dec 12th, 2018, 9:40pm

I have  large garage building with a large 1st floor the ground floor is concreat block cavity wall and the 1st floor is timber frame, I want to convert the 1st floor to accomadation  the timber frame construction is slate on c24 cls stud with a membrain, do I need to continue the cavity
Wall up to the internal roof line maintaining the 100mm cavity gap and use c16 cls  creating an internal stud wall with  cellotex  insulation board
will this comply with building regs
Also do I need to use insulation board on the outer stud also

Thanks in advance

Title: Re: double stud wall
Post by woodsmith on Dec 12th, 2018, 11:39pm

There are a lot of things to take into consideration for a conversion like this and I think that, as you will need to get building permission anyway, your local planning dept should be your first point of contact. You will need to ensure you have suitable floor joists, fireproofing and means of escape as well as insulation and ventilation requirements etc etc...

Nearly all timber frame walls have a brick or block outer skin and this may be what your building control officer will insist on. It is possible to create a single skin timber wall which would have a small cavity on the internal face to run services and which may comply with regs but you will need to get professional advice as I think for this conversion building control will want full detailed plans rather than just a building note.

Title: Re: double stud wall
Post by CWatters on Dec 14th, 2018, 12:24pm


Perhaps see if your Building Control Officer can spare you some time onsite. He's not obliged to until you make a Building Control Application and pay the fee so ask nicely if he could spare half an hour at his convenience. If he says no then you will need to find someone familiar with the Building Regs to take a look.

If the ground floor will remain a garage then you will need to pay attention to the risk of fire spread through the floor/ceiling. May need another layer of plasterboard downstairs and attention to any gaps that might exist where services may go upstairs. These might be hidden in walls or behind panelling?

The external walls upstairs will need to meet the fire and sound transmission regs but how much work that would involve I can't say. It may depend on the proximity to other buildings or the site boundary.

Best case I think you would be looking at Rockwool batts between the existing studs then Celotex over the studs, a vapour barrier then plasterboard.

Worse case may need to take off the slate and fit some kind of cement fire board and replace the slate then do as above.

Lot of concern over fire spread in converted and refurbished buildings since Grenfell if not before.

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