Insulating a garage - turn it into a simple office space - assume I'm an idiot

[mushymat]

Okay, Im not a total idiot but still...

I have a large double garage which already has a partition down the middle - other than that is single brick, concrete floor construction with two single-glazed windows.

Building a stud wall/adding buttons to the walls is a piece of cake. Where I'm a little confused about what kind of insulation I need and how best to apply it to minimize dampness.

I've heard some say I need an air gap between the single brick wall and insulation, while others have said a simply damp-proof sheet/membrane between the wall and insulation will do the trick (with no real gap). On top of either id be installing plasterboard.

As well as this Id like to insulate the floor - my thinking is to add more buttons to the floor, add insulation, and OSB on top.


the space would then be heated with either electric rads, or a diesel heater
any help would be appresiated

 

[mrrusty]

Build a wooden stud wall box inside the garage with a ventilated cavity to the single skin brick. VCL on the inside of the studs, either wall batts or PIR insulation in the wall, PIR in the floor and loft insulation above the ceiling. If using wall batts, you will need a breathable membrane on the outside of the studs to keep the insulation in place. On the garage floor, lay some thin battens, then cross batten with say 2x3's with PIR between, then chip floor. The thin battens will ensure some ventilation.

 

[jeds]

while others have said a simply damp-proof sheet/membrane between the wall and insulation

Don't know where you got this from but it is completely incorrect. Whatever you do, don't do that.

Adding internal insulated stud works well. Follow mrrusty's spec. Otherwise adding a PIR thermal laminate plasterboard also works well and gives you a higher thermal value - although possibly a bit more expensive and slightly trickier to do if you're considering doing this yourself.