The deck is the structural plywood or OSB between the trusses and the underlayment. It is the layer that holds the entire roof system in place, and it is almost always the part of a roof that determines whether the field material above stays attached in a major wind event.
The 2026 Florida Building Code carries forward the deck standards established in 2023, with two clarifications worth knowing.
The baseline
For new construction or full re-roof in 2026:
- Plywood: minimum 15/32" thickness (commonly called "1/2-inch"), exposure-rated, attached with 8d ring-shank nails.
- OSB: same thickness, same fastener.
- Nailing pattern: 6 inches on center at panel edges, 12 inches on center in the field, for most of the state. The HVHZ requires 4 inches at edges and 6 in the field.
These are the patterns that earn the highest wind-mitigation discount on the OIR-B1-1802 form. Older deck patterns — 6d nails, wider spacing — earn less.
Re-nailing existing decks
When the field material comes off for a re-roof, the deck is exposed and inspectable. The code requires bringing the deck attachment up to current standard at that point. This is the "re-nailing" line item on most re-roof contracts.
A typical re-nailing on a 4,000 sq ft roof adds roughly $1,200 to $2,400 to the project cost. It also adds five to seven points to your wind-mitigation discount, which on a $4,000 premium is typically $400-$700 per year.
The 2026 clarifications
The 2026 update specifies:
- Deck repairs over 25 sq ft must be inspected before the underlayment goes down. This addresses a common dispute where rotted plywood was replaced but not photographed for the wind-mitigation report.
- OSB and plywood may not be mixed on a single slope. Older homes with patched-in OSB over original plywood need uniform decking on each plane.
How to verify yours
You cannot see the deck from the attic on most homes — the underlayment is in the way. Your wind-mitigation inspector documents it during the post-installation walk for a re-roof. If your current report does not list the deck attachment in detail (gauge, length, spacing), the inspector did not actually verify it, and you may be earning less credit than you are owed.
A note on tongue-and-groove
Some older homes — particularly mid-century coastal — have tongue-and-groove board decks rather than panel decks. These are not code-compliant on their own and require a panel overlay before re-roofing. The overlay is mandatory; we have walked away from projects where homeowners wanted to skip it. The cost of the overlay is meaningful but it is the difference between a code-compliant assembly and one that will not pass inspection.
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