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

[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 deck through leaks around penetrations, aging seams, or damaged flashing. Flat roofs are especially vulnerable to ponding water, where even a small puddle that doesn't drain properly can slowly seep into the deck below.

In some cases, condensation plays a role. Poor attic ventilation or insulation can allow moisture to build up beneath the roof surface, contributing to rot without any obvious leaks. Over time, even minor issues can cause significant damage if they go unnoticed.

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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 creates a ripple effect that can compromise your roof’s performance and your building’s safety. As the wood deteriorates, it loses strength, which can lead to sagging areas or uneven surfaces. Water that continues to reach the decking can speed up the damage and reduce the lifespan of your entire roofing system.
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Beyond the structural concerns, damaged sheathing can lead to other issues, including:

• 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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Not every roof needs a sheathing inspection every year, but you should consider having your roof sheathing inspected if:

• 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 review
• 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 safeguard your building from hidden damage—and avoid costly surprises later.

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Let Us Take a Look Before It Becomes a Bigger Problem

Not sure if your roof sheathing is in good shape? Our team at Flat Roof Pros specializes in flat roof inspections and can identify hidden damage before it turns into a costly repair. We’ll assess your roof’s condition, explain your options, and help you make the right call for your property.
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Call us today at (855) 771-0111 or request a free estimate online—because what’s underneath matters just as much as what’s on top.

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