Is it called roof decking or roof sheathing?
Short answer. Both. Roof decking and roof sheathing mean the same thing on most houses: the layer of plywood, OSB or boards nailed to the rafters or trusses that the underlayment and shingles attach to. Building codes tend to say sheathing, while roofers and contracts often say decking.
Where you will see each word
- Building codes usually say roof sheathing.
- Roofing contracts and crews often say decking or deck.
- Insurance estimates often list it as sheathing, with the material and thickness, such as OSB or plywood.
- Shingle instructions may say deck or roof deck.
Related terms
- Plank or board decking: solid 1x6 or 1x8 boards, common on older homes.
- Skip or spaced sheathing: boards with gaps, originally used under wood shakes. Asphalt shingles need a solid deck over them.
- CDX plywood: a common construction grade of plywood.
- OSB: oriented strand board, the most common roof panel on newer Georgia homes.
- Radiant barrier sheathing: OSB with a foil face toward the attic to reduce heat.
How to tell what you have
Look up from the attic. Large panels with visible wood strands are OSB. Layered veneers at the edges are plywood. Long narrow boards are plank decking. A shiny foil face is radiant barrier sheathing. Note any stained or sagging areas while you are there.
Why it matters
Your contract or claim may price decking per sheet, and knowing the type and thickness helps you check that replacements match. Panel types are compared in OSB vs plywood roof decking, and the deck's place in the system is shown in roof anatomy explained.