Attaching Advantech subflooring to the underside of an exposed floor assembly
My question is what fasteners should I use when attaching subflooring on the bottom side of a raised floor? Specs below.
I know that Huber recommends #8 or #9 screws, but given that the sheets will be inverted and not really bearing on anything underneath I am concerned about the possibilities of eventual tear-out of sheets through the screw heads.
So, what about using 4″ Simpson SDWS screws? They have a nice, wide low-profile head that I can probably Liquid Flash over. I know they’re not Huber-approved, but neither is an inverted panel.
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I’m in zone 6 and the floor assembly is on piers, 6″ off grade. Underneath is 12 mil poly and 4″ of trap rock.
From the bottom up:
Advantech X-Factor subflooring (inverted and attached to the rims and joists through the rigid panels with something?)
1 1/2″ rigid (EPS or XPS?)
– Liquid Nails Projects & Foamboard High Strength Paste Adhesive to glue the XPS to the joists and rims on the top side, and to the faces of the Advantech on the bottom side
13 3/4″ Unfaced batts (compressed to 11 1/4″ for R-42)
Advantech X-Factor subflooring
-Tytan Subfloor Pro High Yield Adhesive to glue the subfloor to the joists and rims, and .131 nails
Some kind of wood flooring
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Replies
Tiziano,
You are building for the apocalypse again :) Forgetting the contribution of any adhesive (which I would omit), the pull-through resistance of a single standard screw in 1/2" Advantech is about 60 lbs. So a single screw would support the entire sheet.
:) :) :)
Thanks Malcolm.
Just curious why Advantech? It's like 80 lbs per sheet which is a lot to hold overhead while you screw it in.
Also, ring shanked nails in a nailer would save time and money over screws.
The Huber rep suggested it, as did someone else in another thread.
I like the ring shanked idea. Guess I was fixated on screws due to the diameter of the heads.
How does one fasten subfloor sheets to the bottom of joists, 6 inches above grade?
One way is here: https://www.finehomebuilding.com/project-guides/insulation/air-sealed-and-on-piers
But I'm framing in two halves, upside down. Once the joists and rims are attached, I'll add the rigid and then the Advantech (X-Factor version). Then, me and numerous guys will flip and place on the piers. Once attached, I'll add the batts and finally the topside Advantech.
Resurrecting this thread because I have a related question.
It looks like my helpers will be more off than on. As such, I'm likely doing most of this on my own. That possibility reminds me of the fact that my floor assembly may well be uncovered at times.
I've ordered a 50' x 50', 20 mil tarp to try to cover the entire structure at night and on rainy days. But, should wind take it or tear it, then what?
Any thoughts on covering the entire floor with an EPDM pond liner (40 to 60 mil)? Once fully sheathed in I'd slice the liner out at the inside and outside edges of the plates. It would also serve as a plate gasket (which I don't think I need, but maybe it would be a good air seal there).
Tiziano,
I've done exactly what you describe with a pond liner. It worked well. Much easier to work on than poly or a tarp.
Thanks Malcolm. Pond liner ordered.