Mike Hozjan
I'm sold on a metal roof. Yes it will be going over the asphalt shingles. However each sales rep is pushing the virtues of his own system and frankly do not know who to trust. My questions are: 1) Will strapping (horizontal & vertical) under the steel roof promote mold? Or as the other rep suggests putting the steel roof directly on the shingles with a membrane in between promote mold? 2) Will strapping weaken the wind resistance of the steel roof. We get some crazy winds blowing from all directions on top of the hill here. 3) Does a polymer coating like plastisol shrink causing the steel to rust? Thank you.
Eric Novotny
An informed customer is the Best Customer!
Mike, 1. Strapping, if done properly, should provide for an air channel beneath the roof and keep the roof closer to ambient temperature. This should keep condensation at bay as well as keep ice damming to a minimum. 2. If done properly, no. 3. I am not super familiar with that coating, but I can't imagine a reputable panel maker using a coating technology that would do that.
Guest User
I am getting a metal roof and had a question. I have spoken to two different contractors and have gotten two different answers. Would putting a wrap over the shingles (they are in good shape) and wanted to make sure there would be air flow or if this would be necessary in this case or do I need the wood strips or have the shingles removed? Lowes hard wear said they have to remove the shingles and install the metal. I also spoke with the local building inspector and he said to have shingles removed due to air flow/ ventilation, and would not recommend anything other than removing the shingles. Any advice would be good.
Eric Novotny
An informed customer is the Best Customer!
I am not sure I understand the question? The shingles have nothing to do, directly, with the air flow. Above deck venting is a good idea, but not necessary if the attic is currently vented. Can you post up a picture?
Dick Bus
Mike, Plastisol is the typical coating used in Canada because of the low Ultra Violet sunlight in your part of the world. I recommend PVDF coatings in the US. Chad, Eric is correct. Above sheathing ventilation is a good idea. You also need a good quality underlayment. The eaves and valley should have a high temperature peel and stick. Mike and Chad, I recommend that you use a manufacturing member of the Metal Roof Alliance as all of us have agreed to promote top quality products. thanks for using a metal roof.

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