I have an integrated garage with a bedroom above it and the bedroom is always cold.
I have removed the ceiling in the garage below and there is no insulation whatsoever!
The ceiling joists (or floor joists if your in the bedroom) are 7", so I was thinking of using some 100mm celotex between the joists, then some fireshield plasterboard in the garage
Do I need any sort of vapour/moisture barrier?, Its not a problem to take up the floorboards from the bedroom, and should I push the celotex right up to the floorboards to leave an airflow gap between the plasterboard or could I completely fill the joists with insulation? or should I support the celotex away from the floorboards and the plasterboard?

I don't think that it really matters, unless you have removed some sort of moisture barrier.

I filled mine with loft insulation type material from above as I was required to do to keep the building inspector happy. Think it might be less likely to let a draught through that way?

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Mike

When you say you have removed the ceiling do you mean all of it ?

There needs to be at least a double layer of plasterboard for fire regs/building regs and if you are keeping a car in the garage i would be putting a vapour barrier up as well.

Really take the guesswork out and make a quick call to your building regs bloke

Once ceiling is sorted I would insulate from the top unless you are fitting a complete ceiling .....

Fire shield board or double plaster board, fill void solid plus vapour control barrier, tape all joints.

Thanks cotswold,
Should the vapour barrier go on the bedroom side or the garage side of the insulation?
If I fill the complete void is it ok to mix 100mm celotex with the rest cheap loft roll insulation?

I've only removed one board from the garage, only the rear half of the garage is boarded.

Bedroom is above rear half of garage, the front half of garage has flat roof.

The void to the left of the pipes and cables continues into the lounge which could explain why its cold in there too??