Rotting Roof Decking 

What is Roof Rot? 

Roof rot occurs when the roof decking becomes infested with fungi that feed on the wood. This happens when the moisture content of the wood reaches high enough levels to create a habitat for fungal growth. Visually, the spores usually look like red or brown dots that mature into white strings or even balls of white. But different kinds of fungi can have a different appearance and color. If unresolved, the fungi in rotting decking can spread to the rafters and begin to threaten the structural integrity of the roof. 

Common Reasons for High Moisture Content in Roof Decking 

These are the most common reasons why roof decking is exposed to excess moisture. 

• The attic is poorly ventilated 
• Ice dams have formed on the roof during the winter
• There are leaks from damaged shingles or roof punctures  
• A skylight is improperly sealed or installed 
• Storm damage has left an opening in the roof (from things like falling trees or branches) 

Dry Rot Versus Wet Rot 

Wet rot is used to describe fungal species that feed on wood with high moisture content (usually 50% or higher). Wet rot occurs when wood has been heavily saturated with water or experiences continual exposure to high moisture conditions. 

Dry rot describes fungal species that do not require as much moisture to eat away at wood (usually wood with 20% to 30% moisture content). Dry rot requires less moisture to thrive compared with wet rot, although it still needs moisture.  

Both occur because of circumstances where excess moisture has infiltrated the wood.  

Signs of Roof Rot in Your Roof Decking

If you are concerned about the presence of roof rot, the first place you can look is your attic. Check the rafters and decking for dark patches or discoloration in the wood. The colors can vary and you may see white, brown, black, yellow, or another shade that looks unusual or unnatural to the wood. You may want to feel the wood to see if it is soft, sponge-like, or brittle to the touch.

On the outside of your home, you can look for waves or bulges in your roof. This would indicate an advanced state of decay. A roof inspector can remove shingles and check the state of the decking if there are any areas where you believe moisture penetration has occurred.  

To summarize, take note of any of the following if you suspect roof rot: 

• Discolored wood in your attic
• High humidity in your attic
• Problems with shingles or holes in your roof 
• Extremely dry or cracking rafters 
• Bulging or wavy areas on your roof

How Professionals Repair Roof Rot 

For the area affected, a roofing professional will remove shingles, flashing, underlayment, and nails. The process can be more time-consuming if there are many layers of shingles. 

The rotted decking will be sawed and pried out. 

The section removed will ideally cover at least two rafters. New decking will be cut to fit and installed. 

Decking needs to be the same thickness so shingles lay flat.

The roofer may take extra precautions and recommend special surface treatment to apply to the decking or waterproof tape to seal the seam where the old and new decking meet. 

How to Prevent Roof Rot 

Here are the best ways you can protect your roof deck from a fungal infestation. 

• Keep your attic well ventilated: Ensure you have sufficient vents. Even if you have a ridge vent or other roof vents, you may want to add a fan-powered vent, gable vents, and soffit vents to improve airflow.
• Prevent water pooling / stop ice dams from forming: Keep your gutters clear with regular cleanings. Do the same for your roof valleys. Keep them cleared from debris. 
• Have your roof inspected and repaired. After heavy storms, have a professional inspect your roof to ensure there are no entry points for moisture.   

Professional Help for Damaged Roof Decking from Honest Abe

At Honest Abe Roofing, we've been repairing damaged roofs for well over a decade. Our team understands the fastest way to get your decking restored and replaced, so that your home is protected from further damage. If you want an inspection of your roof so you can find out what damage is present, we will come out and inspect it at no-charge to you. 

For more solutions for roof damage, give our team a call today at (844) 298-4100 or find a roofer near you.