Identify the deck instead of assuming it is plywood
Residential decks may use wood structural panels or boards; commercial buildings can use other deck types. Ask the contractor to identify what is known before work and what will be confirmed after exposure. Panel sheathing advice should not be applied to a steel or concrete deck.
Owens Corning’s cited underlayment instructions require a structurally sound, prepared deck. Water staining alone should prompt evaluation of condition and cause; it is not a substitute for deciding whether a particular deck area is serviceable.
Separate deck repair from a structural concern
Ask for photographs and the reason each area is proposed for replacement. Softness, loss of integrity or an unsuitable fastening surface needs an appropriate repair decision. Suspected framing, support or load concerns may require a qualified structural professional.
For wood-panel replacement, panel selection, support, fastening and joint spacing need to follow the applicable design and product requirements. APA provides installation guidance for rated roof sheathing; it does not establish a single thickness or fastening pattern for every roof.
Correct the reason for deterioration
Ask whether a roof leak, flashing defect, condensation issue or other condition contributed to the damage. Replacing the visible deck section without addressing that condition can leave the owner with an incomplete repair. Keep the deck records with the final roof documents.