How often should roof decking be replaced?
Short answer. Roof decking does not need replacing on a schedule; sound, dry plywood or OSB can last as long as the house, through two or three shingle roofs. It is replaced only where it is rotted, delaminated, soft, broken or too thin, and on a typical Georgia reroof that means a few sheets, not the whole roof.
What gets a sheet replaced
- Rot from a long-term leak around a chimney, pipe, valley or skylight.
- Delamination or swelling in OSB or plywood that soaked up moisture, often from a poorly vented attic.
- Soft or spongy spots the crew feels underfoot after tear-off.
- Edge rot along the eaves where gutters overflowed or drip edge was missing.
- Gaps or broken boards on older plank decks.
When the whole deck gets replaced or covered
- Spaced board decking left from an old wood shake roof, which cannot hold shingle nails properly.
- Widespread delamination from years of attic condensation.
- Decking too thin for the rafter spacing, which sags between supports.
These cases are uncommon on homes built in recent decades, but they do turn up on older houses.
Why nobody can count sheets in advance
Decking is hidden until the old shingles come off. From the attic you can spot dark staining, daylight or sagging, and soft areas on the roof are a clue, but the real count comes during tear-off. That is why most contracts list a per-sheet price for decking replacement instead of a fixed total. Ask for photos of every sheet replaced and a count on the final invoice. More on materials in OSB vs plywood roof decking, and on how attic moisture ruins decking in roof ventilation basics.