What is roof decking?
Roof decking is the structural board material, typically plywood or OSB, fastened to the roof framing (rafters) that serves as the base layer for shingles and underlayment.
The layer of plywood or OSB sheets fastened directly to your roof rafters is called roof decking. It acts as a solid substrate that shingles, felt, and underlayment are attached to, making it the bridge between your home's frame and the weather-facing roof system.
In Hartford Metro homes, this decking typically consists of either plywood (more common in older construction) or oriented strand board (OSB), with thickness usually between 1/2 inch and 3/4 inch depending on rafter spacing. The boards are nailed or screwed to the rafters below and must be securely fastened to handle wind loads and distribute the weight of shingles, snow, and ice.
Water damage is the primary concern with roof decking. When shingles fail, ice dams form, or flashing leaks, moisture infiltrates the decking and causes rot, which weakens the entire roof structure. Visible sagging, soft spots when walked upon, or staining from the attic side are signs of decking failure. Compromised decking usually requires replacement during a major roof repair or full roof replacement, as the integrity of this layer is essential to supporting new shingles and ensuring a watertight roof.