insulation

[Graham]

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D\

=A0 =A0 =A0 =A0|

=A0 =A0 =A0 =A0|

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D/- Hide quoted text -

Thanks for all the replies. In answer to the question posed.

1. The garage is still used for cars and junk.
2. The ceiling joists in the garage ceiling are covered by what looks like a fireproof plasterboard (asbestos?)
3. The option of lifting the floor above is not a viable option for me. Dave thanks for the mathematical answer to my question. Just what I wanted to hear. Harryagain windows double glassed, door very draughty. I will do something about that. I=92m thinking I will give it a go. I shall stick it up as suggested but will not screw in case the plasterboard is asbestos. As I am not familiar with Celotex could someone provide me links to the specific product I need and to the recommended adhesive. Again many thanks. Graham

[Huge]

Thank you - I shall put that on the list.

[Phil L]

Using polystyrene in this situation is a very bad idea - the smalles of fires in the garage would result in the stuff giving off some very toxic fumes, not to mention the thick black smoke.

To the OP, use rockwool or glasswool, anything else is dangerous

[Phil L]

Sticking celotex over the ceiling would cost more than doing it properly, and that is to pull the ceiling down, filling the gap with rockwool (insulation and fireproofing) and re-boarding.

Don't forget you'll need to double board the ceiling aftertwards, or use fireboards

[Dave Liquorice]

If going to the trouble of pulling the garage ceiling down I'd put PIR foam insulation into the joist spaces. Better insulation for a given thickness and easier to stuff a ridged board into the gap that a floppy roll of rockwool or flexable batt.

Aye.

[ARWadsworth]

Good point. And I would not want that under my bedroom floor.

Again, I have to menion the electrics:-) Polystyrene and PVC cables do not mix well.

[ARWadsworth]

Maybe there is a time vs cost issue. Even a DIYer has to balance those two up.

[John Rumm]

Celotex in one of the "well known brands" that make PIR insulating boards. Kingspan is probably the other equally well known one. However there are lots of makers of the stuff now, and prices can vary dramatically. In generic terms, foil faced Polyisocyanurate (PIR) boards are what you are looking for.

Last time I asked at a builders merchant about Celotex, I was told £27 a sheet (8x4' in 50mm thickness). In the end I found a local supplier of boards made by Ecotherm, at £14 each for new or £12 for seconds.

Where about in the country are you?

If the ceiling is rough or uneven then I would use expanding foam - a few large blobs dotted about the board, push it into place and support for a bit until stuck.

If you have a reasonably flat ceiling, then you could go for the carpet fitters favourite spray on impact adhesive. Spray ceiling, spray board, let the glue go tacky/dry and slap it in place. It will stick solid on contact.

[John Rumm]

Pull down and reuse the plasterboard? Easier said than done in some cases. If buying new plasterboard, and rockwool, I doubt there is much difference in price.

Only if you take down the original fire break.

[Phil L]

He only needs to pull down a 3ft strip along the middle of the garrage and poke the rockwool in with something, it's messy, but a lot cheaper and more effective than using celotex on the ceiling. IMV the gap between garage and bedroom should be insulated otherwise the cold air (from joist ends meeting the cavity) will blow around, making the celotex redundant.

Making a 3ft gap will take a few 6X3 PB's to repair

The PB is the firebreak, usually 2 X 12.5mm, cross-jointed, or a single layer of pink 12.5mm fireboards

[John Rumm]

Not sure why you think it will be more effective - its only got slightly better than half the insulation value of the PIR.

You also have to take into account the effect that the insulation could have on wiring in the ceiling void.

This depends a bit on the actual construction of the place. A moden build would have joist hangers built into the inner leaf of masonry, and hence no holes to the cavity. A very old one will have joists embedded in masonry, but solid walls....

Probably worth the OP having a look first to see what the situation actually is.

That was my point - if he leaves that in place and adds insulation below it, then there is no need for a new fire break.

[george [dicegeorge]]

I'm sticking up cheap kingspan seconds with pinkgrip dryfix plasterboard foam and a pinkgrip gun, only expands to double, not ten times as do most foams.

But the gun and cleaner is expensive for a one off job.

[g]

[Graham]

Hi all

Again thanks for the input. I have definitely decided on PIR insulation fixed up by expanding foam adhesive. John in answer to your question I am in Hampshire. Before I get stuck in a couple more questions.

1. As the boards are not exactly the size I need how do I cut it.
2. In my application should the foil face up or down.

Regards Graham

[John Rumm]

ok, so my supplier in Benfleet is probably too far to make it worthwhile...

Its cuts with a sharp knife or a panel saw. The latter makes dust. I usually use a fresh blade in a "snap off" blade knife and use it at about full length (for 2" thick boards).

Note the real branded celotex also has fibreglass strands in it that make it a bit more tricky to cut.

Most boards are foiled on both sides. However you usually want the foil where you want the vapour barrier. In your application it probably does not matter much if it is single sided since you are in effect insulating the outside of the warm envelope.

[Graham]

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D\

=A0 =A0 =A0 =A0|

=A0 =A0 =A0 =A0|

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D/- Hide quoted text -

Hi

A final thank you to all. I shall get on with the job and start a new thread if I get into trouble.

Regards Graham