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Wood Structural Panels vs. Plywood Sheathing vs. Plywood

Wood Structural Panels vs. Plywood Sheathing vs. Plywood

Wood Structural Panels vs. Plywood Sheathing vs. Plywood

While designing wood framed shearwalls using capacities provided out of AWC table 4.3A, what is the difference between Plywood Siding and Wood Structural Panels. For example, 3/8" plywood siding with 6" edge nailing has a unit shear capacity of 450 plf while 3/8" wood structural panels with 6" edge nailing has a shear capacity of 615 plf (8d nails for each). Is the plywood siding referring to particleboard? If I need the capacities for the wood structural panels, how do I specify it on my drawing? Is 3/8" plywood clear enough or do I need to call out OSB? Any help is appreciated.

RE: Wood Structural Panels vs. Plywood Sheathing vs. Plywood

I'm not sure the technical difference between plywood siding and structural panel that is made of plywood. In my mind plywood siding probably has some pattern on it and is acting as cladding. The reduction in value might come from the fact that it is acting as cladding (i.e. moisture reduction) or maybe the groove patterns reduce the thickness. This is a total guess.

As for specifying, I generally require the panel to be APA rated. I've also started changing note nomenclature to "WSP" (wood structural panel) as opposed to specifying "plywood" or "OSB" or saying "sheathing" (unless I need OSB). Here is a link to Panel Design Spec. Look at table 12 which ties together thickness and APA rating.

RE: Wood Structural Panels vs. Plywood Sheathing vs. Plywood

Wood Structural Panels as defined by SDPWS is "A panel manufactured from veneers; or wood strands or wafers; or a combination of veneer and wood strands or wafers; bonded together with waterproof synthetic resins or other suitable bonding systems. Examples of wood structural panels are plywood, oriented strand board (OSB), or composite panels."

The referenced table, SDPWS 4.3A further specifies as "Structural I" or "Sheathing" for determining nominal unit shear capacities. These ratings come from APA and are typically based on minimum strength of the panel and the water resistance of the resins used in production. So if you use a wood structural panel (doesn't matter if it's plywood or OSB) with a rating of Structural I, you get 645plf for your stated construction, if you use "Sheathing" rated material it's 615plf if you use 8d nails in your stated pattern, and plywood siding (I take that to mean T-111 or a similar product) gives you the 450plf. Note that particle board sheathing and fiberboard sheathing have their own categories in the table, so no - plywood sheathing is not particle board.

No, just saying plywood or OSB is insufficient for shear wall specs. You need to identify the APA rating as RFreund mentioned. If you used the Structural I values, your drawings need to clearly state that so the framer can order the right materials.

Here's a good write up from APA about Structural I and when to use it: Link

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