Plywood Shearwalls and Horizontal Diaphragms
Plywood Shearwalls and Horizontal Diaphragms
(OP)
I'm looking for allowable shear loads on 3/4" or 1 1/8" plywood shearwalls or horizontal diaphragms. I've checked with APA but they don't go over 5/8" thickness. Where can I find such information?






RE: Plywood Shearwalls and Horizontal Diaphragms
Sustainable, Solar, Environmental, and Structural Engineering: Appropriate technologies for a planet in stress.
RE: Plywood Shearwalls and Horizontal Diaphragms
RE: Plywood Shearwalls and Horizontal Diaphragms
- 6d common - 5/16"
- 8d common - 3/8"
- 10d common - 15/32"
I am assuming that using thicker plywood also will not result in higher allowable design loads. Unless you can justify using higher diaphragm values by using thicker plywood, you will have to use the diaphragm values listed for the thinner plywood.RE: Plywood Shearwalls and Horizontal Diaphragms
Using larger nails than 3" in these 5/8" panels will not result in greater shear resistance, this is true. But is this not due to the fact that it is the various shear resistances within the panel itself that govern the assembly? While the shear resistance of thicker spikes is greater, what good will it do to "walk the nails to the panel" if Vr(max) has already been reached by the panel itself? Incidentally, the WDM also deals with shearwalls and diaphragms using diagonal 19 mm (3/4") and 38 mm (1.5") boarding - Clause 9.5.1.1 The 19 mm boarding is specified with 2.5" common nails (8-penny), and the 1.5" boarding uses 3.5" (16-penny).
As far as I can see, the reason the shearwall tables do not specifically deal with configurations using thicker panels is that these applications are rare, and testing costs money. While the data is there for shear in an individual plywood sheet, (refer to my first post), it is not yet available to us for shearwall and diaphragm assemblies. Does anyone else have any information on this?
Sustainable, Solar, Environmental, and Structural Engineering: Appropriate technologies for a planet in stress.
RE: Plywood Shearwalls and Horizontal Diaphragms
OK, so in order to use the thicker plywood or OSB panels to resist vertical or horizontal shear I'll need to insure that the nails used meet the proper penetration and diameter requirements.
This is fine but I have two questions:
1. The longer the nail becomes, the bending stress increases exponentially. This has to have an effect on the overall capacity. The failure mechanism changes from possible panel tear or nail rip, to nail bending and pull out. With 99% of all residential floors being 3/4" panels you would thing somebody like the APA would address this through testing.
2. I need a reference to justify these panels to a building department plan checker. Does anyone have some literature stating that thicker panels may be used but with a topped out upper limit based on testing?
RE: Plywood Shearwalls and Horizontal Diaphragms
Additionally the building code books present simular shear capacities. For higher values I specify double studs and plywood both sides. Check foundation attachment methods.