pressure treated firring strips?

Guest User
was told that after a few years that screws would back out of pressure treated wood and cause problems with a metal roof. is this true?
Guest User
I really do not know for certain as I do not manufacture that type of roofing. Al can probably answer this question based upon his experience as a contractor a few years back. However, certain treated lumber will have chemicals which can react badly against the back of metal roofing so I probably would not use treated lumber. However, even beyond that, most residential metal roof systems are recommended by their manufacturers to be installed over decking, not furring strips. The main exception would be the batten-mounted horizontal shake and tile profile products. Never embark on the installation of any product without full instructions from the manufacturer.
Guest User
You need to be careful here for several reasons. Treated lumber is typically not kiln dried after treating and therefore will undergo a good bit of shrinkage as it drys --- this is what will lead to the screws appearing to become loose. It is really the wood that shrinks away from the connection. Most newer treated lumber contains coppers as part of the treatment chemicals. This can be very corrosive to steel fasteners if not designed to work with treated lumber.. this will certainly affect fasteners for any roofing material that is used. You will need either a stainless fastener, or one specifically coated to resist this chemical treatment.
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