roof and wall air barrier/underlayment

Asked October 26, 2016, 3:49 PM EDT

I'm building a shed that has to be built of non-combustible materials. Concrete slab, fire treated studs and rafters, fire-treated plywood for wall and roof sheathing, HardiPlank siding and trim, asphalt shingles.
I would typically use Grace Ice and Water Shield on the roof sheathing under the asphalt shingles, and Tyvek on the wall sheathing under the HardiPlank. I need something like those to control water and air infiltration.
Both may be combustible, but are sandwiched between non-combustible materials.
Can I use those?
If not those, what can I use?

Norfolk County Massachusetts

3 Responses

Thanks for your question.

I looked up some information about the fire performance of Ice and Water Shield used in an assembly that includes asphalt composition shingles for the roof cover. This roof covering maintained its Class A fire rating when used in this assembly, so you would be ok. Whereas I didn't find specific information about the wall assembly you specified, I don't think you should worry about using it. If your house experiences a flame and/or radiant heat exposure that degrades the fiber cement siding, the potential contribution of the housewrap product won't matter.

I hope this has been helpful.


Thank you - very helpful!

Brookline, MA