Insulating garage ceiling below bedroom

[seebo]

Hi we had an extension done over our garage few years ago. The bedroom above the garage is always freezing cold only warms up when we put an extra electric heater on which is very costly.

someone suggested to me that the garage ceiling needed to be properly insulated.
I know our ceiling was never insulated properly as our builder always took short cuts, he put small amount of rockwool in the ceiling.
It has been suggested that i should get insulation boards up which will prevent the cold rising from the garage into the bedroom. I dont mind having that done as long as it stops the cold.

My question is: will the insulation boards stop the cold rising up into the bedroom.
which insulation boards are best to use.
The garage ceiling is plastered so will the plaster need to be removed or can
the boards be placed over the plaster and replastered.

Thanking you in advance any advice will be appreciated.

 

[securespark]

This is a thread I posted a while back:
https://www.diynot.com/diy/threads/insulating-bedroom-over-garage.472196/

 

[securespark]

If, unlike me, you have a clear, unfettered ceiling (no pipes cables etc run across), and you can afford to take away a little head height, I would create a void and fill it with 200mm Celotex.

 

[seebo]

Thanks for your reply. As far as I know the ceiling is clear of any cables and pipes,
Do we need to remove the plaster to put up celotex boards. Or can they go over the plaster and skimmed which is the best way,

 

[Tigercubrider]

Would you need to skim them?
I would be tempted to either stick them up and overboard with ply or plasterboard, or create panels by fixing ply to the celotex before mounting the unit on the ceiling? Possibly painted white first?
Is that ok fire regs wise?

 

[seebo]

Thanks that's helpful !!
Sorry to sound stupid but would we need to remove the current plaster boards which have been skimmed and painted or can we stick the celotex straight on the painted ceiling, then place plaster board skim and paint. ??

 

[freddiemercurystwin]

No need to remove the plasterboard, add your insulation, 100mm is fine, then plasterboard over if you don't like the look of the foil on the celotex. The only hassle will be finding the joists to screw into.

 

[seebo]

Thanks for the advice this is just what I needed to know.