Types of Roof Decking and How Rotted Decking is Replaced

Roof decking, sometimes called roof sheathing, is the structural surface your shingles or roofing material are installed on. When this decking becomes rotted from long-term moisture exposure, it can no longer properly support the roof system and must be replaced to prevent sagging, leaks, and structural damage. Rotted roof decking is most often discovered during a roof replacement, but it can also be found during leak investigations or attic inspections.


The replacement process begins by carefully removing the roofing materials in the affected area, including shingles, underlayment, and fasteners. Once the decking is exposed, contractors inspect the surrounding wood to determine how far the rot has spread. Any compromised sections are cut out back to solid, healthy wood. New decking panels or boards are then measured, cut, and securely fastened to the roof rafters or trusses to restore the roof’s structural integrity. After replacement, new underlayment and roofing materials are installed to complete the repair and protect the new decking from future moisture intrusion.


Homes can have different types of roof decking depending on when they were built. Older homes often use solid plank decking made from individual boards installed side by side. These planks are durable and strong but can develop gaps over time as wood shrinks and expands. When replacing sections of plank decking, contractors typically match the thickness and spacing or upgrade small sections with plywood for better uniformity.


Plywood decking became common in mid-to-late twentieth century construction. It is made from layered wood veneers bonded together, creating a strong, stable panel that resists splitting and provides consistent support for roofing materials. Plywood generally holds fasteners well and performs reliably when properly protected from moisture.


OSB, or oriented strand board, is the most common decking material in modern construction. It is made from compressed wood strands bonded with resin. OSB is cost-effective and structurally strong, but it is more vulnerable to swelling when exposed to prolonged moisture compared to plywood. Once OSB swells and deteriorates, it usually must be fully replaced rather than repaired.


Regardless of the decking type, rotted sections should never be ignored. Compromised decking can lead to uneven shingle installation, persistent leaks, and reduced roof lifespan. Professional replacement ensures the roofing system remains structurally sound and able to perform as designed.


If you are planning a roof replacement or suspect hidden water damage, having your roof decking evaluated can prevent costly surprises and ensure your new roof is built on a solid foundation.


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