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TOPIC: Rust

Spray on insulation/rusted roof

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We just moved in to a 1984 log home with a metal roof. When the metal roof was installed, they didn't use any plywood sheeting. We have a cathedral ceiling and essentially, there are just the vertical roof rafters with horizontal 1 X 4 stringers approximately 2' on center. They nailed metal roofing to the stringers and then sprayed polyeurothane foam up onto the metal roofing from beneath - I guess they stood in the living room and sprayed up. They then finished the interior ceiling with tongue and groove. Apparently, over the years the rubber bushings around the nails wore out, water got in and just sat up there on top of the foam causing the metal to rust out. Nobody that we've had estimates from seems to be familiar with this kind of roof construction. If we take up the existing metal, the insulation comes off with it. I talked to an insulation company and they still apparently do this spraying directly on metal. Any suggestions would be most appreciated. Thank you!
Guest User

11/24/2004
You should be able to leave the existing roof in place and install a new metal over. Choose a system that is designed to mount on battens and you should take the opportunity to bring the roof up to code and install ventilation. Assuming you have a vertical rib panel, I would strap the roof vertically over the old metal preferably directly over the existing rafters and fasten them down through. The code requires a minimum od 1" of air space, so consider using a 2x3 or 2x4. Then I would install a high quality underlayment as a moisture barrier and the the metal roof on horizontal strapping. Make sure you pick a substrate that is G90 or AZ50 and has a long lasting coating such as PVDF, SMP or granular. Check our web site as we have products designed for this application at www.duraloc.com.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/24/2004