I've now lined out the walls of my sectional concrete garage (tile battens,
Quinntherm, OSB) and am about to move on to the ceiling. The garage roof is
corrugated galvanised steel, not particularly thick, and it's open to the
air on all four sides: the gaps between the top of the concrete and the
steel are loosely covered by 6"x6" 90 degree steel angle. Here's a pic from
before the walls were done:

http://i246.photobucket.com/albums/g...geinterior.jpg

The steel roof suffers very badly from condensation, which obviously I want
to eliminate. In a previous thread, the general recommendation was to fit a
false ceiling incorporating Celotex or similar (Quinntherm is an
equivalent), ideally leaving a complete air gap between the Celotex and the
steel. Two questions arise from this:

Would it would be desirable to seal the edges of the false ceiling to the
tops of the interior walls, in effect creating a sealed box (apart from
inevitable gaps around the door) inside the original garage?

If I use a lightweight ceiling material (I'm thinking of uPVC T&G cladding)
could I get away with just sticking it to the foil surface of the Celotex?

Many thanks for any thoughts and suggestions.

Bert

On 19/09/2011 11:01, Bert Coules wrote:
I've now lined out the walls of my sectional concrete garage (tile
battens, Quinntherm, OSB) and am about to move on to the ceiling. The
garage roof is corrugated galvanised steel, not particularly thick, and
it's open to the air on all four sides: the gaps between the top of the
concrete and the steel are loosely covered by 6"x6" 90 degree steel
angle. Here's a pic from before the walls were done:

http://i246.photobucket.com/albums/g...geinterior.jpg

The steel roof suffers very badly from condensation, which obviously I
want to eliminate. In a previous thread, the general recommendation was
to fit a false ceiling incorporating Celotex or similar (Quinntherm is
an equivalent), ideally leaving a complete air gap between the Celotex
and the steel. Two questions arise from this:

Would it would be desirable to seal the edges of the false ceiling to
the tops of the interior walls, in effect creating a sealed box (apart
from inevitable gaps around the door) inside the original garage?

Yup - stops warm wet air getting up into cold spaces...

If I use a lightweight ceiling material (I'm thinking of uPVC T&G
cladding) could I get away with just sticking it to the foil surface of
the Celotex?

I would have thought so, yes. Quick squirt with expanding foam on the
back, prop into position and leave for an hour...



--
Cheers,

John.

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\================================================= ================/

John Rumm wrote:

Yup - stops warm wet air getting up into cold spaces...

OK, thanks. That should be fairly easy to arrange.

...could I get away with just sticking it to the foil surface of
the Celotex?

I would have thought so, yes. Quick squirt with expanding foam on the
back, prop into position and leave for an hour...

I've never had much luck with expanding foam. And I've never used it as an
adhesive - I was think more of a Sticks Like... type of product. Wouldn't
expanding foam tend to push the cladding away from the Celotex, unless the
propping-up was over the whole surface?

Bert

On 19/09/2011 12:21, Bert Coules wrote:
John Rumm wrote:

Yup - stops warm wet air getting up into cold spaces...

OK, thanks. That should be fairly easy to arrange.

...could I get away with just sticking it to the foil surface of
the Celotex?

I would have thought so, yes. Quick squirt with expanding foam on the
back, prop into position and leave for an hour...

I've never had much luck with expanding foam. And I've never used it as
an adhesive - I was think more of a Sticks Like... type of product.

That would work as well...

Wouldn't expanding foam tend to push the cladding away from the Celotex,
unless the propping-up was over the whole surface?

Not really - it does not expand with much force if constrained. You can
get a low expansion version designed for board fixing as well.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:

You can get a low
expansion version designed for board fixing as well.

Ah, thanks. I might try that.

Bert

In article , Bert
Coules writes
I've now lined out the walls of my sectional concrete garage (tile battens,
Quinntherm, OSB) and am about to move on to the ceiling. The garage roof is
corrugated galvanised steel, not particularly thick, and it's open to the
air on all four sides: the gaps between the top of the concrete and the
steel are loosely covered by 6"x6" 90 degree steel angle. Here's a pic from
before the walls were done:

http://i246.photobucket.com/albums/g...geinterior.jpg

The steel roof suffers very badly from condensation, which obviously I want
to eliminate. In a previous thread, the general recommendation was to fit a
false ceiling incorporating Celotex or similar (Quinntherm is an
equivalent), ideally leaving a complete air gap between the Celotex and the
steel. Two questions arise from this:

Would it would be desirable to seal the edges of the false ceiling to the
tops of the interior walls, in effect creating a sealed box (apart from
inevitable gaps around the door) inside the original garage?

Absolutely.

If I use a lightweight ceiling material (I'm thinking of uPVC T&G cladding)
could I get away with just sticking it to the foil surface of the Celotex?

Have you decided how to fix the insulation yet?

If not, how about tiling battens on edge, fitted lengthways between and
fixed to those deep timber members with the insulation flush fitted
between them? Then foam fill, cover with foil tape and screw 3mm ply to
the battens to finish, nice & cheap and less work than the tongue &
grooving. There will be a minor cold bridge at the battens but I
wouldn't worry for a workshop. A temporary counter batten will hold up
the insulation while you foam it and save you cutting it for a tight
fit.

You could do without the ply but as it is a workshop the insulation will
get dinged.

Do I remember you saying you were dropping to 25mm for the ceiling to
keep the headroom up? If so then 19x38mm battens on edge would leave a
minimum gap to the underside of the roofing of 13mm. It's a light enough
structure for this to work. Battens can drop a bit if you stick with the
thicker insulation.

Battens at 600mm centres will save the ply sagging but means you'll need
to cut the insulation.

Btw, squeezing out lots of sticks like from a shed caulk gun is a bit
wearing on the forearms as it's quite thick.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

"fred" wrote:

Have you decided how to fix the insulation yet?
If not, how about tiling battens on edge, fitted lengthways between and
fixed to those deep timber members with the insulation flush fitted
between them?

I've arrived at almost exactly the same idea, but - at the higher end of the
garage, at least - I have room to lay 1" insulation *above* the battens
rather than between them. The battens would be purely to stop the
insulation sheet sagging (and I've just seen that you mention this approach
later on in your post). Of course I'd have to rely on the weight of the
insulation (which isn't much, even in an 8'x4' sheet) to hold it down onto
the battens while the foam or other adhesive dried.

Then foam fill, cover with foil tape...

Cover the foam-filled gaps, you mean? Will that really make an appreciable
difference?

...and screw 3mm ply to the battens to finish...

That would be cheaper than the T&G, though I would want to paint it.
Individual T&G planks would be a lot easier to work with though. There are
advantages both ways: I'll give your idea some thought.

Thanks very much.

Bert

In article , Bert
Coules writes
"fred" wrote:

Have you decided how to fix the insulation yet?
If not, how about tiling battens on edge, fitted lengthways between and
fixed to those deep timber members with the insulation flush fitted
between them?

I've arrived at almost exactly the same idea, but - at the higher end of the
garage, at least - I have room to lay 1" insulation *above* the battens
rather than between them. The battens would be purely to stop the
insulation sheet sagging (and I've just seen that you mention this approach
later on in your post). Of course I'd have to rely on the weight of the
insulation (which isn't much, even in an 8'x4' sheet) to hold it down onto
the battens while the foam or other adhesive dried.

Then foam fill, cover with foil tape...

Cover the foam-filled gaps, you mean? Will that really make an appreciable
difference?

Well, over any foam, any joints and the edges of the battens but now
that you mention it, it may be a bit of an unnecessary extravagance.

For moisture laden domestic environs it's meant to complete the vapour
barrier, maybe not so important for the workshop but it would at least
make sure that it's all airtight. It's fairly cheap and the adhesive is
guaranteed for long term use, unlike some cheaper duct tapes.

...and screw 3mm ply to the battens to finish...

That would be cheaper than the T&G, though I would want to paint it.
Individual T&G planks would be a lot easier to work with though. There are
advantages both ways: I'll give your idea some thought.

Just floating some ideas in case it helps once you get to grips with the
job.

Thanks very much.

You're welcome
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********