Celotex between rafters, polstyrene over. Vapour barrier ?
 

Hi,

Im in the process of insulating the roof of my garage.

I am planning on using 50mm Celotex between the rafters. Due to cost,
I was planning on using 25mm polysterene from B&Q over.

Would I still need the vapour barrier plasterboard ? Or if I ditch the
polysterene could I just tape up the joints where the Celotex meets the
rafters and use standard plasterboard ?

Thanks,

Matt

Celotex between rafters, polstyrene over. Vapour barrier ?
 

Celotex between rafters, polstyrene over. Vapour barrier ?
 

Celotex between rafters, polstyrene over. Vapour barrier ?
 

Ian Stirling wrote:
wrote:
Hi,

Im in the process of insulating the roof of my garage.

I am planning on using 50mm Celotex between the rafters. Due to cost,
I was planning on using 25mm polysterene from B&Q over.

Would I still need the vapour barrier plasterboard ? Or if I ditch the
polysterene could I just tape up the joints where the Celotex meets the
rafters and use standard plasterboard ?

Take sheet of non-vapour barrier plasterboard.
Dilute PVA to milk-like consistency.
Arrange some way to prop up the sheet so that it's off the floor,
vertical, or sloping slghtly backwards, with the long side parallel to
the floor.
Spray a meter with the PVA solution from a small pump-up sprayer.
Lay two lines of kitchen foil, slightly overlapping.
Spray another meter, repeat.

This gets you a foil coated bit of plasterboard for well under 30p, and
in under 5 min or so.


Whereas the extra cost of the foil backed plasterboard is probably about
10p for the same area..

Celotex between rafters, polstyrene over. Vapour barrier ?
 

On Wed, 29 Nov 2006 13:43:20 +0000 The Natural Philosopher wrote :
Whereas the extra cost of the foil backed plasterboard is probably
about 10p for the same area..

If you can find it in stock .... Wickes don't sell it, not mine anyway

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk

Celotex between rafters, polstyrene over. Vapour barrier ?
 

wrote in message
oups.com...

Hi,

Im in the process of insulating the roof of my garage.

I am planning on using 50mm Celotex between the rafters. Due to cost,
I was planning on using 25mm polysterene from B&Q over.

Would I still need the vapour barrier plasterboard ? Or if I ditch the
polysterene could I just tape up the joints where the Celotex meets the
rafters and use standard plasterboard ?

why plasterboard a garage roof/ceiling? Plasterboard won't perform well in
an unheated building. Where foil backed PB is specified in construction
it's to prevent warm moist air from an inhabited space condensing out in a
cold space. You seem to be expecting the vapour barrier to prevent moisture
vapour entering your garage. Not necessary due to ventilation of the garage
space and would be a bad thing for your roof structure.

Jim A

Celotex between rafters, polstyrene over. Vapour barrier ?
 

The Natural Philosopher wrote:
Ian Stirling wrote:
wrote:
Hi,

Im in the process of insulating the roof of my garage.

I am planning on using 50mm Celotex between the rafters. Due to cost,
I was planning on using 25mm polysterene from B&Q over.

Would I still need the vapour barrier plasterboard ? Or if I ditch the
polysterene could I just tape up the joints where the Celotex meets the
rafters and use standard plasterboard ?

Take sheet of non-vapour barrier plasterboard.
Dilute PVA to milk-like consistency.
Arrange some way to prop up the sheet so that it's off the floor,
vertical, or sloping slghtly backwards, with the long side parallel to
the floor.
Spray a meter with the PVA solution from a small pump-up sprayer.
Lay two lines of kitchen foil, slightly overlapping.
Spray another meter, repeat.

This gets you a foil coated bit of plasterboard for well under 30p, and
in under 5 min or so.


Whereas the extra cost of the foil backed plasterboard is probably about
10p for the same area..

Oh well.
I got quoted an extra fiver per sheet.
Kitchen foil is only 10p/sheet or so.

Celotex between rafters, polstyrene over. Vapour barrier ?
 

On 29 Nov 2006 04:07:48 -0800, a particular chimpanzee named
randomly hit the keyboard and produced:

Im in the process of insulating the roof of my garage.

I am planning on using 50mm Celotex between the rafters. Due to cost,
I was planning on using 25mm polysterene from B&Q over.

Why are you insulating the garage roof? Is it for frost protection
(with some low-level heating) or are you going to heat it
significantly? If the former, then you probably won't generate enough
condensation to worry about. If the latter, then you're going to need
more insulation anyway.

You'll get better value from your insulation if you use the Celotex
over the rafters and the polystyrene between. There is heat lost
through the rafters and the more insulation you can cover them with
the better.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

Celotex between rafters, polstyrene over. Vapour barrier ?
 

Hugo Nebula abuse@localhost wrote:
On 29 Nov 2006 04:07:48 -0800, a particular chimpanzee named
randomly hit the keyboard and produced:

Im in the process of insulating the roof of my garage.

I am planning on using 50mm Celotex between the rafters. Due to cost,
I was planning on using 25mm polysterene from B&Q over.
snip

You'll get better value from your insulation if you use the Celotex
over the rafters and the polystyrene between. There is heat lost
through the rafters and the more insulation you can cover them with
the better.

To put some numbers on this - wood has a conductivity of about three
times that of rockwool or polystyrene, and six times that of kingspan.

Celotex between rafters, polstyrene over. Vapour barrier ?
 

In article ,
Tony Bryer writes:
On Wed, 29 Nov 2006 13:43:20 +0000 The Natural Philosopher wrote :
Whereas the extra cost of the foil backed plasterboard is probably
about 10p for the same area..

If you can find it in stock .... Wickes don't sell it, not mine anyway

Mine does, and since it's only a few hundred yards away, that's
where I buy it. I think they might have foil-backed only in 9mm
though.

--
Andrew Gabriel

Celotex between rafters, polstyrene over. Vapour barrier ?
 

I am planning on using 50mm Celotex between the rafters. Due to cost,
I was planning on using 25mm polysterene from B&Q over.

Technically, the top layer of insulation has to be better or the same than
the bottom layer of insulation. That means that if you have 50mm Celotex
between the rafters, you can have either have up to 50mm below the rafters,
or 50mm or more above the rafters. The top layer being polystyrene makes it
even worse.

This is to avoid condensation forming between the insulation layers.

If you are going to suck it and see, then DEFINITELY use vapour check
plasterboard, as that will significantly reduce the problem. Taping the
celotex with foil tape would, I presume, have a similar function to vapour
check p/b.

Christian.

Celotex between rafters, polstyrene over. Vapour barrier ?
 

Ian Stirling wrote:
The Natural Philosopher wrote:
Ian Stirling wrote:
wrote:
Hi,

Im in the process of insulating the roof of my garage.

I am planning on using 50mm Celotex between the rafters. Due to cost,
I was planning on using 25mm polysterene from B&Q over.

Would I still need the vapour barrier plasterboard ? Or if I ditch the
polysterene could I just tape up the joints where the Celotex meets the
rafters and use standard plasterboard ?
Take sheet of non-vapour barrier plasterboard.
Dilute PVA to milk-like consistency.
Arrange some way to prop up the sheet so that it's off the floor,
vertical, or sloping slghtly backwards, with the long side parallel to
the floor.
Spray a meter with the PVA solution from a small pump-up sprayer.
Lay two lines of kitchen foil, slightly overlapping.
Spray another meter, repeat.

This gets you a foil coated bit of plasterboard for well under 30p, and
in under 5 min or so.


Whereas the extra cost of the foil backed plasterboard is probably about
10p for the same area..

Oh well.
I got quoted an extra fiver per sheet.
Kitchen foil is only 10p/sheet or so.

enough for mow much? and then add in glue, your time...?

I didn't think plasterboard was much more than a fiver a sheet last time
I looked anyway..

Celotex between rafters, polstyrene over. Vapour barrier ?
 

The Natural Philosopher wrote:
Ian Stirling wrote:
The Natural Philosopher wrote:
Ian Stirling wrote:
wrote:
Hi,

Im in the process of insulating the roof of my garage.

I am planning on using 50mm Celotex between the rafters. Due to cost,
I was planning on using 25mm polysterene from B&Q over.

Would I still need the vapour barrier plasterboard ? Or if I ditch the
polysterene could I just tape up the joints where the Celotex meets the
rafters and use standard plasterboard ?
Take sheet of non-vapour barrier plasterboard.
Dilute PVA to milk-like consistency.
snip
This gets you a foil coated bit of plasterboard for well under 30p, and
in under 5 min or so.
Whereas the extra cost of the foil backed plasterboard is probably about
10p for the same area..

Oh well.
I got quoted an extra fiver per sheet.
Kitchen foil is only 10p/sheet or so.

enough for mow much? and then add in glue, your time...?

I didn't think plasterboard was much more than a fiver a sheet last time
I looked anyway..

I got quoted 10 quid a sheet for vapour barrier, 5 for not.

Tesco do foil for 68p for 3m^2.
It used about a litre of PVA for 24 sheets.

It takes about 3 minutes per sheet to do (once I stopped being silly and
getting a perfect mirror finish on each sheet of plasterboard, with no
wrinkles and perfect butting joins, which was admittedly very pretty,
but diddn't add a whole lot).