Spray foam insulation on a metal garage roof
Bert Coules
metal roof which suffers badly from condensation. Has anyone any experience
with spray-on foam insulation on such a roof, either professionally applied
or DIY? For a DIY product see for example,
http://www.spray-insulation.co.uk/ .
I've also thought about lining the roof with a thin polystyrene veneer such
as Warmaline (but would it follow the corrugations?) or using Celotex sheets
(which would create lots of air gaps) but I've been told that the foam is
the most effective way of stopping the problem.
If anyone's tried it, or has any thoughts, I'd be grateful for any info.
Tim Lamb
Coules <ma...@bertcoules.co.uk> writes
>As I mentioned in another thread, I have a garage with a corrugated
>thin metal roof which suffers badly from condensation. Has anyone any
>experience with spray-on foam insulation on such a roof, either
>professionally applied or DIY? For a DIY product see for example,
>http://www.spray-insulation.co.uk/ .
>
>I've also thought about lining the roof with a thin polystyrene veneer
>such as Warmaline (but would it follow the corrugations?) or using
>Celotex sheets (which would create lots of air gaps) but I've been told
>that the foam is the most effective way of stopping the problem.
Sheet steel roofing is available with a layer of *felt* attached to the
underside. I don't understand the mechanism but it may just retain the
condensation; allowing it to evaporate when the sun comes out.
>
>If anyone's tried it, or has any thoughts, I'd be grateful for any info.
I've not tried it but I have heard that a fine mesh net fitted close to
the underside and trapping a layer of air can work. I think moisture in
the trapped air layer condenses but because convection is interrupted
further moisture can't reach the cold surface.
I would be surprised if your concrete slabs are not tongue and groove
and even more surprised if someone does not suggest the angle grinder
solution:-)
regards
>
>
>
>
>
--
Tim Lamb
Bert Coules
> Sheet steel roofing is available with a layer of *felt* attached to the
> underside. I don't understand the mechanism but it may just retain the
> condensation; allowing it to evaporate when the sun comes out.
Thanks for that. I'm not sure I'd be too happy about having a large expanse
of water-soaked felt just above my head...
> I've not tried it but I have heard that a fine mesh net fitted close to
> the underside and trapping a layer of air can work.
That's intriguing. There's enough headroom - just - to hang a Celotex or
similar ceiling below the metal roof making no contact at all with it
(except perhaps for however it was fixed). Possibly that might be the best
solution. I imagine it would also be necessary to seal off the ends of the
roof, which at the moment are just open to the air, through the troughs in
the corrugations.
> I would be surprised if your concrete slabs are not tongue and groove...
This ought to be in the other thread I suppose, but judicious probing with
knife and drill into the mastic seals between the panels has revealed plain
(and not particularly close-filling in places) butt joints.
> ...the angle grinder solution:-)
Could still be the way, if the bolts won't budge.
Bert
Owain
> As I mentioned in another thread, I have a garage with a corrugated thin
> metal roof which suffers badly from condensation.
Have a look at anti-condensation coatings used in shipping containers.
Owain
Bert Coules
> Have a look at anti-condensation coatings used in shipping containers.
Thanks for that. As with the spray foam there seems to be a divide between
DIY products and professionally applied solutions. A quick search hasn't
turned up much in favour of the DIY paints, though that might simply reflect
the fact that people are usually more apt to complain than to praise.
Here's what seems to be a typical DIY product, Johnstones Anti-Condensation
Paint: http://tinyurl.com/69vrf8e . Has anyone here used it, or something
like it?
Bert
Andrew Mawson
"Bert Coules" <ma...@bertcoules.co.uk> wrote in message
news:tsidnd7PKfCca3DQ...@brightview.co.uk...
I had the roof (fibre reinforced corugated cement sheets) of my 2000
sq foot barn sprayed as I was using it as a workshop. I had 100mm
sprayed on the ceiling and 75mm sprayed on the walls which I then
lined with 18mm osb3 board. It has been entirely satisfactory. Mind
you it cost a fortune. Took four 205 litre drums of the foam and two
blokes 3 days.
AWEM
Bert Coules
> I had the roof (fibre reinforced corugated cement sheets) of my 2000
> sq foot barn sprayed as I was using it as a workshop... Mind
> you it cost a fortune.
My garage roof is a tad more modest at 140 sq ft. Within the DIY
possibility-band, I'd have thought. Good to know it worked for you; thanks.
Bert
It was im
news:tsidnd7PKfCca3DQ...@brightview.co.uk...
As I mentioned in another thread, I have a garage with a corrugated thin
---------------
I can vouch for the 'felt' coated sheeting. I have had it on a building with
a roof cover of approximately 30ft x 20ft for the last five years and I have
never yet seen any sign of condensation or damp on it and never a drip -
excellent in my experience. It's a very thin layer of this stuff - not
exactly felt - applied to the underside of the sheets that apparently traps
condensation and allows it to evaporate when the conditions change. It does
appear to work.
Neil
Bert Coules
> I can vouch for the 'felt' coated sheeting. I have had it on a building
> with a roof cover of approximately 30ft x 20ft for the last five years and
> I have never yet seen any sign of condensation or damp on it and never a
> drip - excellent in my experience.
Neil, do you know if it's possible to apply this material (or have it
applied) to an existing plain metal roof? I must do some more searching.
Thanks very much.
Bert
Bert Coules
> felt just above my head...
Tim, I'm sorry, that was an over-hasty response. Searching around, I've
discovered a custom-made felt-like membrane called Drip Stop which is
specifically designed to hold water as condensation develops and then let it
evaporate later. Clearly, this is exactly the material which you were
referring to. Unfortunately, it doesn't seem to be available as a separate
product for application to an existing roof, but only (as you also said)
prebonded to manufactured panels. Pity.
Bert
Bert Coules
John Rumm
Not tried it. While I would be very wary of using it in some of the
cases they promote (i.e. on the underside of a tiled roof where it will
trap any moisture that gets through against the timbers), it sounds like
a reasonable proposition for a basically sound garage roof with not much
in the way of wood about.
--
Cheers,
John.
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Bert Coules
> it sounds like a reasonable proposition for
> a basically sound garage roof with not much in the way of wood about.
Yes, I agree. Not particularly cheap, though, (although if it's as
effective as they claim, that wouldn't be a major consideration) especially
once you take into account that the corrugations in the sheet metal increase
the surface area to be covered by a considerable factor.
I'm trying to find out if the water-retaining feltish membrane which Tim
Lamb mentioned can be obtained for DIY application to an existing roof. No
luck yet, though.
Bert
![george [dicegeorge]'s profile photo](http://lh3.googleusercontent.com/a-/ALV-UjVy3egmWxdo6kgdNwXDn-6EE54MDMuR9kO5wF-DhVhewlzxjNY=s40-c)
george [dicegeorge]
(where the corrugations above the kingspan are open to the air outside
amd thus ventilated and any leaks would drain out)
and the kingspan is sealed with foam like pinkgrip
so warm moist air wont get up there to condense,
[g]
Bert Coules
> Perhaps a celotex or kingspan seconds roof under the corrugated
> (where the corrugations above the kingspan are open to the air outside
> amd thus ventilated and any leaks would drain out)
> and the kingspan is sealed with foam like pinkgrip
> so warm moist air wont get up there to condense,
I have wondered about something like that. Would it be sufficient, do you
think, to attach the Celotex directly to the underside of the roof (which
would leave lots of individual air gaps but put the false ceiling in
intermittent contact with the real one) or should it be suspended a little
below (which would leave one overall air gap and no direct contact at all)?
Bert
george [dicegeorge]
with pinkgrip foam or similar,
then screwed into the battens
you wouldnt puncture the roof!
[g]
Bert Coules
> perhaps if you glued battens to the metal
> with pinkgrip foam or similar,
> then screwed into the battens
> you wouldnt puncture the roof!
Thanks, but I'm not worried about puncturing the roof (Celotex even in large
sheets, is surely light enough to be glued to the metal sheeting). I just
wonder if a complete air gap would be more effective than a partial one.
Bert
John Rumm
> John Rumm wrote:
>
>> it sounds like a reasonable proposition for
>> a basically sound garage roof with not much in the way of wood about.
>
> Yes, I agree. Not particularly cheap, though, (although if it's as
> effective as they claim, that wouldn't be a major consideration)
> especially once you take into account that the corrugations in the sheet
> metal increase the surface area to be covered by a considerable factor.
Although a flat panel of insulation just below the exiting roof would
not need to cover the extended "as the roof undulates" distance. Could
you afford to lose say 50mm of height?
If you can, then I think I would make a dead man prop, get a couple of
cans of expanding foam, and some ordinary foil faced PIR foam boards.
Squirt a few blobs of foam on the back of each board, and stick em to
the ceiling (using the prop to hold em in place long enough for the foam
to set). Then foam in any gaps at the edge. Tape the joints so that no
moisture laden air can reach the original roof.
You could probably do the whole lot for less than £100 that way.
> I'm trying to find out if the water-retaining feltish membrane which Tim
> Lamb mentioned can be obtained for DIY application to an existing roof.
> No luck yet, though.
>
> Bert
fred
Coules <ma...@bertcoules.co.uk> writes
roofing a tad as any water from future leaks couldn't be held in contact
with the sheeting by contact with the celotex, encouraging rust. You
could easily achieve this with a few thin pads of something stuck to the
sheets of celotex before it goes up. Side nailing into rafters would be
a common way to pin the sheets up and if you leave a slight gap then
foam could be used to seal them up and fix them in place, saving foil
taping. I'd say making the lower face of the insulation air tight to the
room was pretty important to avoid any hint of damp air reaching the
cold sheets. I reckon that seconds of 2" celotex would be about 1/3 -
1/2 the price of foaming.
--
fred
FIVE TV's superbright logo - not the DOG's, it's bollocks
Bert Coules
> Although a flat panel of insulation just below the exiting roof would not
> need to cover the extended "as the roof undulates" distance. Could you
> afford to lose say 50mm of height?
Yes, just - and I think that what you suggest is emerging as the favourite
solution, especially given that I was planning on lining the walls too,
which would create a more-or-less completely sealed box within the original
garage structure.
Many thanks for the thoughts.
Bert
Bert Coules
> The safest bet would certainly be to stand the celotex off (under) the
> roofing a tad...
Thanks for that. As you might see from my earlier reply to John Rumm, this
is definitely emerging as the favourite approach.
> I reckon that seconds of 2" celotex would be about 1/3 - 1/2 the price of
> foaming.
I've bought Celotex seconds in the past but I can't now remember the source.
I'll do some searching around.
Bert
Tim Lamb
My experience of anything glued to the underside of metal exposed to
sunshine is that, eventually, the glue fails. Witness droopy sound
insulation in my tractor cabs:-(
regards
--
Tim Lamb
Bert Coules
> My experience of anything glued to the underside of metal exposed to
> sunshine is that, eventually, the glue fails.
Thanks for the warning. I think securing to the rafters and to new
battening along the sides is probably the way to go.
Bert
John Rumm
One oft seen recommendation is:
http://www.secondsandco.co.uk/
If you are anywhere in reach of Essex, then there is also a very good
place in Benfleet.
Bert Coules
John Rumm wrote:
>> I've bought Celotex seconds in the past but I can't now remember the
>> source. I'll do some searching around.
>
> One oft seen recommendation is:
> http://www.secondsandco.co.uk/
Thanks for that. I found the place where I bought from previously: A&A
Insulation Services in Pontypridd: http://www.aandainsulationservices.com/ .
They've just quoted me £15 each for 2400x1200x50mm Celotex, plus £30
delivery; I'll compare that with Seconds and Co.
Out of interest, I just checked Wickes: their price is £27.98 for singles
(not seconds, of course) reducing to £19.98 each for ten or more.
Bert
John Rumm
>
> John Rumm wrote:
>
>>> I've bought Celotex seconds in the past but I can't now remember the
>>> source. I'll do some searching around.
>>
>> One oft seen recommendation is:
>> http://www.secondsandco.co.uk/
>
> Thanks for that. I found the place where I bought from previously: A&A
> Insulation Services in Pontypridd:
> http://www.aandainsulationservices.com/ . They've just quoted me £15
> each for 2400x1200x50mm Celotex, plus £30 delivery; I'll compare that
> with Seconds and Co.
That sounds reasonable...
Our local place was doing seconds at £12, and new at £14 - but that was
about two years ago before the VAT rise. So I would expect them to be
more now.
> Out of interest, I just checked Wickes: their price is £27.98 for
> singles (not seconds, of course) reducing to £19.98 each for ten or more.
Yup - paying full retail for them is pretty painful. When I wanted a
loft load Jewson wanted about £2,300 for what I needed. The local
supplier did it for £700 inc delivery.