Insulating cavity floor over Garage

[Tyre Tread]

Some advice appreciated please.

We moved into a late 70's build house last year woth a bedroom over the garage.

Over the winter the room got very cold and when I decorated I found, as I suspected, there was no insulation in the cavity between the garage ceiling and the bedroom floor.

The floorboards in the bedroom are difficult to take up but the ceiling in the garage just has 5mm platerboard (I assume its plasterboard).

What would be the best way to insulate between ceiling and floor and what type of board should I replace the existing board with - presumably as over the garage it should be fire retardant/proof?

Edited by Tyre Tread on Monday 1st August 09:56

[DrDeAtH]

Pull the existing ceiling down, stuff at least 150mm rockwool insulation in between the joists.
Staple a vapour barrier across the joists.
Install new ceiling of 2 layers of 12mm plasterboard. Stagger the joints between layers.
Skim with 2 coats of finish.

[neth27]

The first thing I would want to know is what is the 5mm boarding, especially if it was built in the 70s.

John..

[ZDW]

Yep find out what that boarding is first. Being in a garage my have meant the boarding needed to be fireproof and in a 70s built garage, asbestos insulation board is was not uncommon. and about 5mm thick too.

If it's not AIB, insulate from underneath the floor, if it is, and is in good condition it'll be cheaper to lift the floor and do from above.

[Tyre Tread]

Thanks gents, the thought it was asbestos has crossed my mind.

How do I identify if it is and what's the likely cost to remove and dispose from a 30 ft sq garage?

It looks quite new - even has boot marks on it in places presumably where it was walked on before it was fitted to the ceiling.

[neth27]

Get a sample tested first.

John.

[ZDW]

You'll need to get it tested but do take precautions when removing a sample. Funny, mine also had boot prints on it too.

Unfortunately the test came back as asbestos insulation board for my garage ceiling. 36m2 of it that cost a small fortune to remove - the whole seal the place up with plastic, air filters, decontamination shower type thing. It had to go because I needed a new garage door and couldn't get on fitted without it being removed.

As said before, get it tested and then decide what to do.

[Little Lofty]

If it is asbestos and you don't want the hassle of removing it you may be able to put a false ceiling below it, you could insulate it with 2 layers of Kingspan type insulation, it wouldn't need fireproofing as the existing ceiling would still be in place.

[Alucidnation]

^ that's what I would be doing.

[Tyre Tread]

Thanks for the information.

I can't put a false ceiling in unfortunately due to the height of the windows and doors.

So what's it likely to cost for 30 Sq Metres if it is asbestos?

[ZDW]

I couldn't put in a false ceiling either - would have need new beams to span the space and that would have made the ceiling far too low. Re price for removal - quotes were averaging £95+Vat per m2

Hopefully you'll discover it's not AIB and be able to crack on with the job.

[Tyre Tread]

ZDW said:

I couldn't put in a false ceiling either - would have need new beams to span the space and that would have made the ceiling far too low. Re price for removal - quotes were averaging £95+Vat per m2

Hopefully you'll discover it's not AIB and be able to crack on with the job.

Ouch! Thanks - me too but I'n worried.

[Equus]

DrDeAtH said:

Pull the existing ceiling down, stuff at least 150mm rockwool insulation in between the joists....

For what it's worth, if the acoustic (ie. noise reducing) properties of the insulation are not a consideration, then PIR rigid foam insulation (Kingspan or Celotex) is roughly twice as efficient as rockwool as a thermal insulator, for the same thickness, if fitted correctly.

[honest_delboy]

Holy thread , etc etc

I'm in the same position, eaves cupboard above garage that's freezing. 1963 house.

There's an awful lot of asbestos sampling companies out there, are they all as good as each other or any recommendations ?