What is roof decking?

Roof decking is the structural sheathing installed directly over the roof framing (rafters or trusses) that serves as the foundation for all other roofing materials. Typically made from plywood or OSB (oriented strand board), this layer is fastened with nails or screws and provides the base to which underlayment, shingles, flashing, and other roofing components attach. In Connecticut homes, standard decking thickness ranges from 1/2 inch to 3/4 inch, depending on rafter spacing and local building codes.

The condition of roof decking directly affects the longevity and integrity of the entire roof system. Water penetration from damaged shingles, ice dams, or failed flashing can cause the decking to absorb moisture and rot. Signs of decking deterioration include soft or spongy spots when walked on, visible sagging or waviness, nail heads that have risen above the surface, or water stains on interior ceilings and attic framing. Once rot develops, the structural integrity of the roof is compromised, and the decking must be replaced before new roofing materials can be installed.

During roof inspections or replacements, contractors assess decking condition by probing suspect areas and observing attic ventilation and moisture levels. If decking rot is discovered during a roof replacement, the damaged sections are typically cut out and new plywood or OSB is installed. Proper ventilation, working gutters, and regular roof maintenance help prevent premature decking failure in Connecticut's freeze-thaw climate.