What is the building code for roof decking?
Short answer. Under the International Residential Code, which Georgia enforces in its 2024 edition with state amendments since January 1, 2026, roof decking must be rated wood structural panels such as plywood or OSB, or lumber boards, sized for the rafter spacing, and asphalt shingles must go on a solid deck. Panels carry a span rating stamp that tells you the maximum framing spacing they are allowed to cover.
The main requirements
- Rated panels. Wood structural panels must meet the federal product standards for plywood and OSB and carry a grade stamp. The stamp shows a span rating such as 24/16 or 32/16, where the first number is the maximum roof framing spacing in inches.
- Span limits. The code's sheathing span table pairs each rating with a minimum thickness. For framing at 24 inches on center, the usual choices are 7/16 inch OSB rated 24/16 or 15/32 to 1/2 inch plywood rated 32/16. Thinner panels between rafters typically need edge support such as panel clips.
- Solid deck for shingles. Asphalt shingles must be fastened to solidly sheathed decks. Spaced boards left from an old wood shake roof need a panel overlay before shingles.
- Fastening. The code's fastening schedule calls for nails along panel edges and in the field at set spacings, commonly 6 inches at edges and 12 inches in the field, with tighter schedules in high-wind areas.
- Bond classification. The stamp also shows Exposure 1 or Exterior, which tells you the panel can handle getting wet during construction.
What this means on a replacement
When rotten or delaminated decking is replaced, the new sheets must meet the current code. If the existing deck is undersized, spaced, or badly fastened, the building department or the shingle manufacturer may require upgrades. Permit and inspection practices vary by Georgia city and county, so the local building department has the final word.
If insurance is paying for a storm replacement, code-required decking work may fall under ordinance or law coverage, see code upgrades and ordinance or law coverage. Compare panel types in OSB vs plywood roof decking and learn about local permits in roofing permits in Georgia.