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Phoebe Southwood Posted: Nov 08, 2007 07:22 PM	Cedar shake shingles Hi Mason - We just learned that we should not have spray foam insulation installed in our attic space (which we are converting into a living area) because the original roofing material that is nailed to the skip lath is cedar shake. Apparently, in Portland, OR when they finally change the roof, they will scrape off the cedar and put down plywood to attach tar shingles to. The advice we were given by our Spray Foam company was to get a new roof now or just wait until we have finally have a new roof. We're looking at potentially 10 more years of this roof being ok. Is there any way we can get around having to wait to spray in foam? Should I nail up thin pieces of wood onto the skip lath to cover the cedar shingles so that when they are scraped off, the foam wont be destroyed? Would that cause a problem with the insulation working properly? Also, we have been told to use open cell foam, but are not sure why we should. Any light to shed on this? Thank you so much.
mason Posted: Nov 09, 2007 12:49 PM	Cedar shake shingles are not an acceptable substrate for sprayfoam, too much movement and they absorb a great deal of water. In order to use sprayfoam to the underside of the deck, you would need to install some type of sheathing under the lath and be able to drain the water if it got past the shingles.

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Comments

Phoebe Southwood

Posted: Nov 08, 2007 07:22 PM

Cedar shake shingles

Hi Mason -

We just learned that we should not have spray foam insulation installed in our attic space (which we are converting into a living area) because the original roofing material that is nailed to the skip lath is cedar shake. Apparently, in Portland, OR when they finally change the roof, they will scrape off the cedar and put down plywood to attach tar shingles to.

The advice we were given by our Spray Foam company was to get a new roof now or just wait until we have finally have a new roof. We're looking at potentially 10 more years of this roof being ok.

Is there any way we can get around having to wait to spray in foam? Should I nail up thin pieces of wood onto the skip lath to cover the cedar shingles so that when they are scraped off, the foam wont be destroyed? Would that cause a problem with the insulation working properly?

Also, we have been told to use open cell foam, but are not sure why we should. Any light to shed on this?

Thank you so much.

mason

Posted: Nov 09, 2007 12:49 PM

Cedar shake shingles are not an acceptable substrate for sprayfoam, too much movement and they absorb a great deal of water. In order to use sprayfoam to the underside of the deck, you would need to install some type of sheathing under the lath and be able to drain the water if it got past the shingles.

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