OT.Roof insulation

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Has anyone has any experience of using a chemical hard setting foam to reinforce & insulate an old slate or concrete tile roof ?

This stuff is applied by an operator on the inside of the roof and is suppose to secure the slates & do away with having to take the whole lot off to reslate using new nails.Almost sounds too good to be true ! Any feedback would be most appreciated.

PS.When are you all expecting to know who will be the next President ?

-- Chris (enquiries@griffenmill.com), November 26, 2000


Hi Chris, I would estimate that 80 % of my business is based on roof repairs. I would be interested to know more about this type of system, as I haven't heard of it before. I'm familiar with a type of foam that comes in a can and is used for residential and on a larger scale commercial insulation. The kind I have seen is uaually a yellow cream color.

I once saw a house where the previous owner(and owner of the foam insulation company) had used this material to cover the entire roof,6 to 8 inches thick, and then painted over it. It sounds like it would work;( sealed, hardened foam protected from the sun by paint), but it only lasted a couple of years. But I realize you are considering a different method. The foam that I described expands as it dries. If your slate is dried out, flaking, brittle, or loose, this type could push it out of place.

Slate is always put over thick felt paper, on a steep roof because it's not designed to be sealed. (If you've seen it sealed, it usually is done after failed attempts to fix the original problem.)

During a heavy, blowing rain, water that goes in the cracks between slate, rolls back out on the slate below. (That is, this how it's supposed to work) If you put slate on a very low pitch roof and water blew in the cracks, it would stay under the slate for a longer time, and have more time to soak through. A question that comes to mind is what kind of change in the natural occuring intake/outtake system will take place in the system you have now? Will the foam trap water in a place that it didn't previously?

Another consideration is ventilation. If this foam seals the entire attic, you want to be sure to put a vent across the ridge. (Entire length is best)

-- Bob Villa Wannabe (Uponthe@roof.com), November 26, 2000.


I have never heard of foam that is used from INSIDE the roof, and cannot fathom how it could hold loose slates from inside. I too am familiar with the outside foam that is sprayed on top of the roof as Bob above covered in his post, and I agree with him that it is shit, do NOT do it.

Is your roof slate? Does your roof have wood sheathing with the slate on top of it? That might sound like a dumb question, but if that is how your roof is constructed, and that would be typical construction, I can't see how doing anything inside the roof, under the sheathing, could possibly hold loose slates on the outside in place. I will also agree with Bob that expanding foam between the slates could possibly destroy the roof.

With what you have told me so far I have to think that it is indeed too good to be true.

-- Uncle Deedah (unkeed@yahoo.com), November 26, 2000.

Uncle Deedah, I was allowing for the possibility that their roof might have large spaces between the sheathing boards.( For those who aren't familiar, these are the boards that the slate shingles lay on.)

-- Bob Villa Wannabe (uponthe@roof.com), November 26, 2000.

That would be the only situation that MIGHT lend itself to this type of procedure, roof nailer boards with spaces vs full plywood sheathing. If it is solid sheathing typical of newer construction I would say that doing anything from the inside would be nearly futile. Even if it is not fully sheathed, I would still have some reservations about the foam ending up between the slate and the wood, which could cause bulging that might dislodge or crack the slates.

Chris, can you see the backs of the slates from inside your attic?

-- Uncle Deedah (unkeed@yahoo.com), November 26, 2000.

I agree that it could even create problems that didn't exist before. Something else to watch for; if you have a have a more solid seal at the bottom of the roof, and water gets in under the slate at the upper roof, or pools of water get trapped and freeze/and expand,.... Then again, it wouldn't cost alot to experiment, if your option is spending thousands...

-- BVW (uponthe@roof.com), November 26, 2000.

The foam I am familiar with is packaged in 12-ounce aerosol cans. This foam expands quite a bit. I am aware of companies that have this in commercial quantities with special aplication equipment.

Is your roof deck made of boards with spaces inbetween? As said before, roof decks typically have felt paper applied over the deck and under the shingles. If your roof does not have the felt, then foam applied lightly to the underside of the boards could adhere the slate shingles to the deck boards. However you would have to be careful not to apply too much or the foam would ooze between the shingles and the deck and expansion would dislodge the shingles. You could apply the foam in several coats, letting the first dry to form a firm base for the rest.

I'd buy a few cans and experiment, then if it worked discuss appication procedures with your contractor.

-- John Littmann (Llittmannj@aol.com), November 27, 2000.

Hi,back again.

Many thanks for all your comments.Bob,I found a site describing the foam at http://www.islrenotherm.co.uk-bba1.html

Apparently you do need to have a 10mm ventilation gap & should not apply to wet or damp timber.Comes with a 25 yr guarentee & takes a day to apply.Means you can keep the original slates & there is very little mess.Slates (real Welsh slates) are now very expensive so this would be good from a historical viewpoint...maybe.

Our roof slates are nailed onto battens (2x1.5 ins) which themselves are nailed across the roof trusses on the outside.Yes,you can see the back of the slates as there are no other boards,paper or felt present. The roof is 95 years old & original & came complete with bats.LOL

-- Chris (chris@griffenmill.com), November 27, 2000.

Bad link,Chris. Keep us posted?

-- BVW (uponthe@roof.com), November 27, 2000.


I read that this technique is being used in preservation projects in New England. I have never read a description of it working or not.

PS.When are you all expecting to know who will be the next President ?

Apparently, at the same time that Charles becomes King.

Best wishes,,,,


-- Z1X4Y7 (Z1X4Y7@aol.com), November 27, 2000.

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