Masonry walls with 2″ XPS and rainscreen siding: Anyone have any experience with a fastening system?
Stevens95
| Posted in Energy Efficiency and Durability on
There are plenty of resources for fastening foam insulation boards on wood frame construction, i.e fastener depth, spacing, foam thickness, etc. Does anyone have any experience with fastening to masonry construction?
I’m putting 2″ of XPS on the exterior of a concrete/CMU building. WRB, 3/4″ strapping and fiber cement siding on top of that. I’ll fasten the XPS with Hilti IDPs. My question is on fasteners. Any ideas on spacing and embed depth into the masonry? I’m thinking tapcons 12″ OC, with 2-3″ embed depth, since concrete has less pull out resistance than wood.
Thanks!
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I'll let others comment on the fastener spacing & type... Hardie punts on the fastener spacing & depths for the furring when hanging it on furring, See comments under "Method 1" on p.4:
http://www.jameshardie.com/d2w/best-practices/appendix-glossary-esr-hz10-us-en.pdf
But 2" foil faced polyiso would be substantially greener than 2" XPS, due to the vast difference in blowing agent impact, and easier to air seal using temperature rated 1.5-2" aluminum tape on the seams. It would have modestly higher average thermal performance too.
Jonathan,
I assume you have already read this GBA article: Fastening Furring Strips to a Foam-Sheathed Wall.
You note that "concrete has less pull-out resistance than wood." That generalization seems over-broad; what really matters is the pull-out resistance (and resistance to shear) of the actual fastener you have chosen to install. I suggest that you call ITW Buildex (800-284-5339), the manufacturer of TapCon fasteners, to discuss this question.
If ITW Buildex reps can't help you, you can always consult an engineer. Make sure that the engineer reads the GBA article I linked to -- it may save him or her some research time.