Garage conversion. Walls and ceiling.

Hi Folks,
Currently gearing up to turn half my garage into a utility/downstairs cloakroom.I received some great advice re stud walls and concrete floors on another post and I now come to how to finish the walls. Obviously one of the walls will be a new stud wall with the necessary insulation in. The remaining three walls are existing. They are currently painted brick. The two internal walls I intend to just dot and dab and then skim. The External wall is solid 9” brickwork and I am thinking that this would be an opportunity to insulate it internally. I realise that when this is done incorrectly then it can cause more problems than it solves. Could anyone explain the best process in insulating without causing damp/condensation issues.

Secondly the garage has a flat roof with a concrete ceiling. Would it be acceptable to just fit a 3x2 frame below this and insulate between the timbers with Celotex or do I need to use a different method. Once again any advice is greatly appreciated. Thanks.

If the garage is attached to the house, you need building regs. So the plans that you need to get drawn up will include the latest building regs specifications on insulation etc.. You will need to follow the cold roof system and the vapour barrier is important. The insulation for the roof used to be 120mm kings pan, I don't know if that's been increased.

Bonni said:

If the garage is attached to the house, you need building regs. So the plans that you need to get drawn up will include the latest building regs specifications on insulation etc.. You will need to follow the cold roof system and the vapour barrier is important. The insulation for the roof used to be 120mm kings pan, I don't know if that's been increased.

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Thanks for the reply Bonni, I'm aware I need to inform building control. My understanding of the "cold roof system" is that below the concrete roof of the garage I would build a timber frame and infill this with the correct thickness of PIR board. underneath this I would need a vapour barrier and then plasterboard and skim. Does this sound about right? I pressume the drywall screws would pierce the vapour barrier, is this an issue? I also assume the insulated ceiling would need a ventilated gap above as would a timber floor. If I left a 50mm gap and made sure the airbrick in the current garage wall is above the insulated ceiling would this also sound like the way to go?

I'm working on a garage conversion at the moment, just thought I'd mention if you are using building regs, insulation values are thicker than you may be intending to use. I was told the walls have to achieve .18 for U value. On a cavity wall with 75mm rock wool already, this will mean using something like 72.5mm insulated plasterboard on the exterior walls.
Can't help with roof, as It's two storey.

For you, I might look at using insulation fixings and drill straight onto wall and not using D&D.

I will be putting 100mm PIR on the floor as well.

HTH?

Good luck.