Roof decking: OSB vs plywood, which is better?
Short answer. Both OSB and plywood make sound roof decking when they carry the right span rating for your framing and are installed and nailed to code, and both are common on Georgia homes. Plywood tolerates getting wet and drying out better and holds up a bit better at the edges, while OSB costs less and is more uniform, so the choice matters most on roofs with moisture risk or during repairs that must match existing decking.
The quick comparison
- Strength: equivalent when the span ratings match.
- Moisture: plywood swells less and dries out better after brief wetting; OSB edges can swell permanently.
- Nail holding: both hold shingle nails well when dry.
- Consistency: OSB has no internal voids and fewer weak spots.
- Cost: OSB usually costs less per sheet.
When it matters most
- Repairs: match the existing thickness so the surface stays flush. A 1/2 inch plywood patch in a 7/16 inch OSB deck, or the reverse, can show as a ridge or dip.
- Moisture-prone attics: with a history of condensation or leaks, plywood is more forgiving, though fixing the ventilation matters more.
- Long exposure: if a deck may sit uncovered in Georgia rain during a project, plywood tolerates it better.
What usually goes wrong
Decking failures in Georgia come from water, not the panel type: slow leaks at boots and flashing, condensation from poor ventilation, and soaked edges where drip edge is missing. Either panel rots when it stays wet.
On a reroof estimate
Ask how damaged sheets will be priced, ideally per sheet in writing, and what type and thickness will be used. Ask whether loose decking will be renailed to the current schedule.
For the full comparison, see OSB vs plywood roof decking, and for how the deck fits the roof system, roof anatomy explained.