Guest User
7/27/2009
I have a metal roof on my house and it was recently damaged by a severe hail storm. The roof I have is insulated underneath with 6" of polyisonine spray foam. Sprayed directly to the underside of the R panel. One of the contractors suggested I just go directly over the existing R panels with new R panels. Will this cause the roof to rust out prematurely ? Would it be better to use a furring strip to create an air gap betweeen the two panels.
Ken Buchinger
NCI Building Systems, Inc.
7/28/2009
A furring strip is not a bad idea. You can create an air gap and vent the cavity between the two roofs to help prevent condensation. You can use a wood 1x4 or you can use a product from a company called Roof Hugger. A word of caution if you use wood - do not use treated wood. It contains copper which is a disimilar material and will cause galvanic corrosion.
Guest User
7/28/2009
What about metal over metal with no furring ?
Guest User
9/3/2009
Ken, what is you're opinion on meatl roof directly over metal roof ? I have a brand new (1yr old) metal roof with isonene spray foam underneath. It was damaged by a severe hail storm. I cant decide if I should go down directly over the existing roof with new metal or use a furring channel between the two. A furring channel gives me an air gap between the two metals which is good but it creates some other problems with my skylight panels and I'm worried that simply attaching a furring channel in the upper rib of the existing panel is not strong enough to hold down the new roof in a strong wind storm. My question is : Do you think going direclty over metal panels with new metal panels will create a rust problem in the future ? I do have 12" of poly spray foam under the existing panel, if that makes a difference?
Guest User
9/3/2009
David, Ken gave you good advice. Do not install metal directly over metal without some type of gap. If you do, and there is a condensation problem, your new roof will deteriorate from underneath. The gap that purlins will give the roof allows for the moisture to dry out. Mathews Roofing Texas
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