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Discussion Starter #1
I am building a roof in a forested area and want to achieve Class A. I am looking at a product (http://www.slatedirect.net/) that is mostly slate.

Will Versashield make this a class A? One or two layers. Over ice and water shield?
 

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When Grace Ice & Water Shield is used under a classified roof covering, it carries the classification of the covering roof. If you use asphalt shingles (mostly class A) over GIWS, it is still Calss A. The classification must be printed on the packaging of the roofing material.
Jim
 
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To clarify my question. Ignore the ice and water shield; that is not the issue. The issue is Versashield (a fire resistant sheeting) affecting the roof rating if a non-class A covering is used. Example - does class C outer layer roofing material + 1 or 2 layers of versashield = class A roof? This appears to be the case in some examples and maybe on the Versashield site.

Vendor has not answered this question.
 

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During the California wildfires, sometimes the only house on a block still standing was the one(s) with metal. There are many good quality stone-coated or non-coated metal shingles that can look like slate, Spanish tile, three-tabs, etc. This is cheaper than actually using slate. The weight restrictions for heavier products such as tile and slate don't apply to something this light.(a definite bonus in earthquake prone areas) DO NOT use cedar shakes or shingle - even fire treated - if you are worried even slightly about fire. The outer layer (slate, cedar, asphalt) is where you get your protection. The underlayment does not offer the protection you are looking for. The MFRs pay for testing and you want to see the Class rating. Pay attention to the roof assembly. If my product was only tested on a concrete or metal roof deck, this would not be applicable to your plywood or OSB deck. Many insurance companies will give you a break for metal, tile, or slate.
 

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My understanding of UL classifications is that the underlayment cannot raise the roof covering classification, unless it has been specifically tested by UL. It can lower it. It will say what the minimum underlayment is in the roof coverings UL Classification Report, ie: 15# UL rated felt is common for Class A asphalt shingles. Unless the Class C roof covering has been tested with Versashield for a higher classification, it is still Class C.
Jim
 
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