[heading-style-h3]Is Your Roof Sheathing at Risk?[heading-style-h3]

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[heading-style-h4]What Causes Roof Sheathing to Rot?[heading-style-h4]

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The number one cause of sheathing damage is moisture. Water can reach the decking through leaks around vents, pipes, worn-out seams or damaged edges. Flat roofs are especially at risk for standing water, where even a small puddle that doesn’t drain properly can slowly soak into the materials below.

In some cases, moisture comes from inside the building. Poor ventilation or insulation can cause warm, damp air to collect under the roof, leading to hidden rot even if there are no visible leaks. Over time, even small problems can cause serious damage if they’re not addressed.

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[heading-style-h4]Why Rotted Sheathing Is a Serious Problem?[heading-style-h4]

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Rotted or weakened decking can set off a chain reaction that affects both your roof’s performance and your building’s safety. As the wood breaks down, it loses its strength, which leads to sagging areas or uneven surfaces. If water keeps getting in, the damage will only get worse and shorten the life of your entire roofing system.

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Beyond the structural concerns, damaged sheathing can lead to other issues, including:

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• Mold and mildew growth, which affects indoor air quality
• Reduced insulation performance, making heating and cooling less efficient
• Potential damage to interior systems like electrical wiring, drywall, and framing
• Higher repair costs if problems spread beyond the roof itself

The earlier these issues are caught, the more manageable the repairs will be.

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[heading-style-h4]How to Tell If Your Roof Sheathing Needs Attention[heading-style-h4]

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Since the roof deck is concealed beneath roofing materials, you won’t always see signs right away. However, there are warning signs property owners should look for.

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If you notice areas of sagging, bubbling, or uneven roof surfaces, it could be a sign that the sheathing underneath is compromised. Soft spots when walking the roof, persistent leaks despite previous repairs, or unusual musty odors in the building are also red flags. If you have attic access, visible dark stains, cracking, or fungal growth on the underside of the decking can signal moisture intrusion.

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Professional roofers are trained to recognize these signs early—sometimes even by subtle shifts in the roof’s feel when inspected on foot.

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[heading-style-h4]When Should You Have It Inspected?[heading-style-h4]

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You should consider having your roof sheathing inspected if:

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• Your roof has experienced recent leaks, ponding, or storm damage
• You're planning a full roof replacement or major upgrades like solar panels
• Your building is over 15 years old and has not had a recent roof inspection
• Moisture issues have been found in the attic or upper levels

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Inspections during these times can prevent small issues from turning into major structural repairs later on.

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[heading-style-h4]Protect Your Building by Looking Below the Surface[heading-style-h4]‍

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Your flat roof’s performance relies on what’s happening below the membrane. Protecting the sheathing layer is critical to ensuring long-term durability, energy efficiency, and safety. Early detection and regular inspections are the best ways to protect your building from hidden damage and avoid costly surprises down the road.