Your home's roof consists of several layers stacked on top of one another. The wood framing sits at the bottom and provides structural support, while the layers above help to insulate your home and protect it from the elements. The solid roof decking – typically made from plywood boards – is sandwiched between the structure and the shingles.

Since plywood is vulnerable to damage from moisture, the underlayment and shingles help to protect it against rain and exposure. When part of the upper layer fails, water can seep into the decking and rot the wood. Rotting decking can cause structural issues or lead to moisture problems within the home, so it is essential to deal with this problem as soon as possible.

Evaluating the Issue

The first step to resolving a problem with your roof decking is to determine the cause and the extent of the damage. Decking rot always occurs due to water infiltration, and this must be the result of a failure of the leak barrier, shingles, or possibly the roof flashing. Water does not necessarily follow a straight path, so the source of the leak may not be above the affected decking.

If you have access to your attic, then looking for signs of leakage or evidence of additional damage is simplest from below. Depending on the severity of the leak, you may be looking for damp spots, mold growth, or other evidence of moisture. You can use what you find to determine how many sections of decking are damaged and also to find the root of the problem.

Repairing the Leak

Leaks often occur due to damaged shingles or underlayment failures. Flashing near chimneys, dormers, or other roof features can also fail and direct water beneath the upper protective layers of your roof. Whatever the case, repairing the source of the leak is essential before proceeding. Without dealing with the underlying cause first, your new decking may suffer the same fate.

Addressing the Rot

You don't need to remove your entire roof when a decking panel rots out. Instead, you can cut out the affected sections and replace them with new plywood or oriented strand board panels. You will need to remove all of the rotted decking to restore the integrity of your roof, so it is essential to discover the full extent of the damage when you are first evaluating the problem.

After installing new decking, you will also need to replace the underlayment and roof shingles. For this reason, it's best to disturb as little of the existing roof as possible. Focusing only on the damaged portions of your roof will minimize both the time and cost of the repair.

To achieve the best outcome, always work with a roofing professional to repair any issues that you discover. An experienced roofer will have the knowledge to find the full extent of the damage and conduct a long-lasting repair. 

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