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Current ceiling is roof, 2 x 8, tong and groove across top of vaulted ceiling beams, 4 x 12's, spaced 8 ft o.c. Pitch is 1.5 in 12. Exterior is tar and gravel with cracks. We are considering replacement by metal roof and intend to remove tar roof because of leaks and not knowing if there is dry rot. What is recommended procedure for best product, roof over old roof or remove old roof. Secondly this is in Florida with hot and humid summers. Can we insulate between roof and metal roofing or do we need to go underneath the wood? We prefer to have the rustic vaulted ceiling beams exposed, so we saw fairly thin rigid sheets of closed cell polyurethane with fair R-value. The roofer we talked to tells us he would use polystyrene. That would soak up moisture if it were exposed to a leak? Your evaluation is appreciated.
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Current ceiling is roof, 2 x 8, tong and groove across top of vaulted ceiling beams, 4 x 12's, spaced 8 ft o.c. Pitch is 1.5 in 12. Exterior is tar and gravel with cracks. We are considering replacement by metal roof and intend to remove tar roof because of leaks and not knowing if there is dry rot. What is recommended procedure for best product, roof over old roof or remove old roof. Secondly this is in Florida with hot and humid summers. Can we insulate between roof and metal roofing or do we need to go underneath the wood? We prefer to have the rustic vaulted ceiling beams exposed, so we saw fairly thin rigid sheets of closed cell polyurethane with fair R-value. The roofer we talked to tells us he would use polystyrene. That would soak up moisture if it were exposed to a leak? Your evaluation is appreciated.
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Hans,
Yours is a unique situation. Let me put forth my thoughts.
Building codes would now require a vented airspace over ceilings such as yours. This ventilation helps with energy efficiency and it also helps to avoid an unhealthy buildup of moisture inside the home. As we make buildings tighter and tighter with better windows, siding, housewrap, doors, etc., we're also making them less breathable so that moisture inside the homes cannot escape. Good ventilation can rectify that situation and avoid unhealthy air and possible mold issues.
1.5:12 is pretty minimal pitch and would restrict you to certain vertical seam metal roofs, primarily those intended for industrial and commercial low slope applications.
I would strongly suggest having a structural engineer review the house in order to determine if it would handle the weight of building a new roof over the old roof. (Removing the old roof would help with the weight situation.) This would allow you to create a ventilated airspace and even to install some insulation if you wish on top of the existing roof or sheathing. You could also create a roof with greater pitch which opens you up to a wide variety of metal products. I would suggest increasing to at least a 3:12 pitch. Putting a metal roof on top also helps with the weight issue as metal roofing is much lower weight than standard shingles.
This would allow you to keep the inside appearance unchanged and yet would create a healthier and more efficient overall roof system.
Good luck.
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Todd:
I know this is an old thread, but it's almost the same issue I have (probably the same style house that were being built around the late 50s early 60s). Do you have any new experience with the same issue? Have you ever used the Certainteed Fintboard CV for this kind of situation? How do you vent the eaves when the T&G extends and there is no soffit cavity? Do you create one to connect to the panel air passages?
Thanks
9/10/2002
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9/11/2002
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