Soft Spots and Rotted Roof Decking: What the Repair Involves

What decking is

Roof decking (sheathing) is the plywood or OSB nailed to the rafters or trusses. Shingles, underlayment and flashing all depend on it. When it gets wet repeatedly, it swells, delaminates and rots, and it can no longer hold nails.

Signs of rotted decking

• A roof that feels soft or spongy underfoot (a contractor will notice this; stay off the roof yourself).
• Sagging between rafters visible from the ground as waves or dips.
• Dark, soft or crumbling wood seen from the attic, often around chimneys, vents, valleys and eaves.
• Shingles that won't hold nails.

Common causes

Long-term leaks, attic condensation, missing drip edge at eaves, clogged gutters backing water up under the roof edge, and failed flashing at walls and chimneys.

How the repair works

The shingles and underlayment over the damaged area are removed. Rotted decking is cut back to solid wood over the framing and replaced with new sheathing of matching thickness, nailed to the rafters. Underlayment and shingles go back on, with any failed flashing replaced. If the rafters or trusses themselves are soft or cracked, they are reinforced or repaired before the decking goes back. During a full reroof, every sheet is checked after tear-off and damaged sheets are replaced. See new roof installation.

Why a general contractor helps

Rotted decking often comes with wet insulation, damaged ceilings and sometimes framing damage. AGCS is a licensed general contractor with in-house crews plus specialty subcontractors, so the repair can include the decking, framing, insulation and interior finishes under one scope. See structural repairs.

Fix the cause

Replacing decking without fixing the leak, ventilation or gutter problem that rotted it means doing it again. See finding the leak source.

Frequently Asked Questions