GRK Fasteners with Zip-R Sheathing
I am sheathing a 26×14 porch addition with 2″ xps under zip system. Lead times on Zip-R were prohibitive and I could not source polyiso locally.
Zip suggests that fasteners penetrate the framing 1.5,” which means I need a 4″ fastener. I don’t have a nailer that will shoot a 4″ nail. So, because the project isnt huge, I intended to hand-drive 20D galvy nails.
What I have found is the heads of the nails will not flush-up with the zip panels, because the force required to do so will compress the foam rather than sink the large nail heads into the panels. This isnt an issue in the middle of my panels, but is a problem at the edges (3″ fastener spacing) because it leaves proud nail heads which will reduce the efficacy of the zip tape.
Long story short, Zip does not officially endorse GRKs. Practically, do you all think I could use a 4″ GRK R4 countersink in this application without concern?
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Would using the ZIP fluid/liquid flashing work better instead of the tape?
I know you said your project is small (I'm assuming not a house) but I asked Patrick McCombe over at FHB if he would ever recommend GRK fasteners with ZIP, and he made a great point: Wall and roof sheathing should be nailed as nails have better ductility which makes them stronger in high winds and seismic events. Nails bend, screws break. Again, perhaps not an issue for you but thought I would share.
The instillation of Zip+R product is highly engineered and heavily tested system to designed to prevent racking while surviving seismic events.
Going off script and substituting unapproved fasteners in the quantity of your own design seems unwise.
> Long story short, Zip does not officially endorse GRKs. Practically, do you all think I could use a 4″ GRK R4 countersink in this application without concern?
Assuming you're in the US, this is not an IRC prescriptive assembly, nor is it a manufacturer tested assembly, so any code official worth their salt would require the design stamped by a registered design professional.
from a structural performance perspective, not having the sheathing in contact with the framing may be problematic. With zip, I understand the insulation is bonded to the sheathing but they have done the work of engineering, adding the 2" of rigid between the studs and zip may effect the overall strength.
> With zip, I understand the insulation is bonded to the sheathing but they have done the work of engineering, adding the 2" of rigid between the studs and zip may effect the overall strength.
The adhesive between the OSB and the polyiso in Zip R is not very aggressive. I actually doubt that they're relying on that adhesive at all for any shear resistance. However, it's still a tested assembly and field made facsimiles are not the same as far as the code goes.
In some areas, you are allowed to use XPS alone. If you are in such an area, then you should be able to do whatever you want with the Zip and fasteners.
If things haven't gotten too far yet, why not do let in bracing? Either the steel variety or the 1x4 versions that I remember from the 50's and 60's. The engineer stamping your plans should be able to guide you to safety and keep any inspectors happy.
If you aren't in a high-wind or seismically active area I wouldn't worry too much about it. The GRKs should be fine.
I’ve been in touch with Huber and respected consultants on my “diy zip-R” approach. Huber of course can’t officially endorse but everyone agreed if I follow Huber’s recommended fastening schedule with nails I should be good to go.
I’m not in a high wind or seismic area (zone 5 MA) — the 2x4 walls are non-structural single story partitions to which I’m adding windows as I enclose an existing post and beam porch.
I underestimated just how resistant the wall stack up would be to hand driving 4” nail heads flush to the zip…at the edges the foam just starts to compress which I’m trying to avoid.
I worry that pulling the existing nails, drilling counter sinks, and re-nailing will weaken the connections so I’m trying to come up with solutions.
All future nails I’ll pre-drill a space for the nail heads to sink into.
But for the already driven nails I’ve even considered taking a flap Disc to them to thin them down or pulling it all off and putting the foam outside the zip…but that has its own challenges.
Given your last post- that it is infill with windows, just get some 4" deck screws with counter sink style heads. Skip the giant nails, grind the heads and add screws where it seems sub par. If you have a shear wall then sheath it direct to the studs and cover with foam and then more zip, to address the shear wall deflection issues.