Cheaper Comfortboard insulation fasteners
I am planning my wall system for a future new home build in Calgary (climate zone 7A) and would like to have an exterior layer of at least 1.5″ thick comfortboard mineral wool. I would also like to use 2×4 battens to limit waviness of the wall, and provide a more solid backing for siding.
With this thickness of material, I’m thinking I would want my fasteners to be at least 4.5″ long so they get 1.5″ embedment into the plywood/stud. I have also read that its best to avoid the zinc plated screws, and stick to corrosion resistance coated or stainless steel screws. I have however had trouble finding such a fastener at a decent price. I can get the stainless steel Heco Topix 6x160mm screws for $1.40 each, or 5″ long Climatek-Coated structural screws for about $1.00 each. This would add up very fast in either case (with screws every 12″ vertically and battens matching studs at 16″ o/c, thats $0.75-1.05 per square foot of wall just for screws).
This got me thinking about what it would take to use much cheaper hot dip galvanized nails. I can get 40d (5″ long) hot dip galvanized nails for $0.17 each. Of course then I need to figure out how to use some sort of squash block to prevent the batten from compressing my mineral wool.
Then an idea stuck that is either total trash, or perhaps genius? A pizza saver (yes that plastic bit you get at the center of delivery pizza) is exactly 1.5″ tall, same as my mineral wool. I’m thinking the prongs might be able to press though the comfortboard and keep a batten from compressing the mineral wool when nailing. I can get pizza savers for less than $0.10 each, and am thinking if i just press one of these into the wool every foot or so, then install the batten and nails over top, total cost is about $0.27 per fastener. Could this keep the battens from compressing when nailing?
The alternative is using pex tubing cut to 1.5″ lengths as a nail sleeve, but i can imagine that being very labour intensive needing to either drill or push that tube through mineral wool and line up all the nails.
For those who have experience installing rain screen battens over mineral wool, does this sounds crazy? Are there other corrosion proof fasteners on the market that perhaps are cheaper that maybe I am unaware of?
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