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TOPIC: General Discussion

Poorly done roof - how to fix?

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Our builder spray foamed under the old aluminum roof. Please see the picture of the roof before the spray foam. It's aluminum sheeting on wood barn board and rafters. Then he drywalled (not sure if there is a vapor barrier) and then put up T&G. We had a little water damage on the wall where it connects to the roof early in the winter. We called in a roofer and he said that builder used a ridge vent that is for asphalt shingles and the roof had been patched too many times. There could be a leak but this would be difficult to find. He suggested replacing the metal roof with a new metal sheet roof and putting down waterproof layer. How do I fix the roof, ventilation, insulation so we don't have a water problem?
Alisha Hirsch

2/14/2011
Based on other post, I would look critically at the roof. This spray foam is popular now, every is doing it. Jury is still out on it. Before doing this though, the builder needs to make sure the roof will not leak. If the foam gets wet its useless. No matter what was told you it will soak in water. Spray foam should have never been installed under a questionable roof. If you do replace the roof, you should look at above sheathing ventilation with a hidden fastener metal roof system over this area. I have never put a exposed fastener roof on a house and never will. The reason - they leak. Having this over a spray foam insulation it could take years and a lot of damage before you even know.
Ronnie Allen

2/17/2011
A 2 lb (closed cell) foam will not accumulate moisture. You can submerge it in water for months, pull it out, dry the surface, and it will have the same mass. The issue with closed cell foam on roof applications is that it will not allow the water to percolate through the foam to show you where the leak is happening and give you any pinpointed locations of the problem. I do wholeheartedly agree that the roof needs a clean bill of health before you foam the underside of the roof. That is an absolute must. I am not sold on the over deck ventilation as there will not be any vapor migration through the foam that would necessitate ventilation. If the purpose of over deck venting is for heat control, that does have application value. I also strongly agree that I am not a huge fan of exposed fastener roofs. They are usually only marginally less expensive and they have much more leak potential built into them.
Eric Novotny
An informed customer is the Best Customer!

2/18/2011
How do I know if closed cell foam or open cell foam is used? When the roof is replaced? What type of membrane should be used under the roof (over the wood and foam)? Attached is a picture of the foam in the roof.
Alisha Hirsch

2/22/2011
2 lb foam will be much more rigid to the touch and cannot be compressed by pressure nearly as easily as 0.5 lb foam. Didn't you have the spray foam work done? Ask your contractor. If you replace the roof, putting the roof down on a system of battens will allow for over deck venting and help mitigate the transference of energy as well as providing for a drying plane. I would use one of the synthetic underlayments that is commonly available under your new roof and preferably something that is recommend by the manufacturer of the new roof material. If that room is being used as living space, you should also check into the code as it pertains to ignition barriers and fire ratings on exposed foam.
Eric Novotny
An informed customer is the Best Customer!

2/22/2011
I have a question about replacing the roof. So the spray foam is under the barn board but there are gaps between the barn board and in these areas the foam is directly on the metal. Can the metal be taken off? Will the spray foam need to be cut? Will chunks break off? Will the roofer need cans of spray foam to fill in the holes? If he roofs over the old roof, then I'm still worried about condensation. Thanks.
Alisha Hirsch

3/23/2011
Spray foam does have very good adhesion and will stick to the roof well. The metal roof will be able to be removed in most cases but if there is considerable contact between the foam and the roof deck, it will be difficult. Any chunks that are removed as a result of the roof removal can be filled selectively with can foam by the roofer.
Eric Novotny
An informed customer is the Best Customer!

3/23/2011