Roof decking and sheathing

Normal function

The deck provides a flat, secure substrate for underlayment and fasteners and transfers roof loads to the framing.

What a homeowner may notice

• Soft or spongy areas, sagging, delamination, fasteners that do not hold, or visible staining.
• Mold or rot around long-term leaks, valleys, eaves, chimneys, and penetrations.
• A roof surface dip that remains after water drains.
• Deck movement or exposed sheathing during tear-off.

Professional inspection

Inspect attic-side surfaces for dark staining, rot, nail withdrawal, deflection, and daylight. During repair or tear-off, probe exposed sheets and confirm framing support, panel edge support, thickness, and moisture condition.

Repair or replacement path

Remove unsound sheets back to supported framing, install code-appropriate replacement sheathing with proper fastening and edge support, then restore underlayment and roof covering. Structural framing damage needs a separate assessment.

Typical materials and equipment

Plywood or OSB of appropriate grade/thickness, fasteners, blocking where needed, underlayment, leak barrier, shingles, and disposal equipment.

When to act

Treat soft or open decking as a priority because it can worsen, lose fastener holding power, and compromise the roof covering.

What moves the price

Hidden rot, panel thickness, framing repair, access, roof pitch, weather, asbestos/old materials, permit requirements, and whether the leak caused interior finish damage.