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Timber Products' APA 303 five-ply Okoume T1-11 siding is listed as a wildfire-area wall assembly with specified grooves, framing and nails.
The 0503 listing describes nominal 19/32-inch panels, sized 4 feet by 8 feet or taller. Groove width must not exceed 5/16 inch, while groove spacing must be at least 4 inches. A narrower groove and a wider interval are separate allowances; neither changes the stated panel thickness.
Installation uses nominal 2-by-4-inch studs at 16-inch centers. The fasteners are 8d nails, identified as 2-1/2 inches long. OSFM names SFM 12-7A-1 for this Okoume T1-11 construction and directs users to Timber Products' instructions and product data sheets for installation details.
Keep the five-ply identity, groove limits and framing-and-nail combination together when comparing a proposed wall to GOVmotus listing 8140-2343:0503. The T1-11 name alone leaves several of those construction choices unspecified.
Documented attributes
Each value below points to its field-level manufacturer, official-listing, test-report, or standard-body evidence.
Timber Products Company (8140-2343:0503). FireApproved. https://fireapproved.com/materials/timber-products-company-8140-2343-0503/. Last verified 2026-08-23.