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Addressing Roof Rot on A Flat Commercial Roof

Addressing Roof Rot on A Flat Commercial Roof

Roof Rot (aka dry rot) is a roof condition to avoid at all costs. It’s ugly, it’s unhealthy, and it’s costly to repair the damage it causes. Roof rot breaks down roofing materials, thereby compromising the roof deck and sheathing. It eats away at wood, making it dry and crumbly. (Roof rot is actually caused by a wood-eating fungus.) Ignoring it is very risky because it grows rapidly — as much as 10 feet in one year — and can lead to leaks and even total roof collapse!

What Causes Roof Rot?

In a word, moisture. Excess moisture can have several causes, but the main culprit is usually an attic that’s too hot and poorly ventilated. This causes high humidity, which translates into the wooden components of your roof being exposed to excessive moisture. It only takes a 20% moisture level (i.e., wood that is damp to the touch) for wood rot to “blossom” and begin sending fine, microscopic strands of gray fungus into surrounding fibers. Other causes of roof rot are also moisture-related, and include:

  • Ponding problems on a flat roof with an inadequate or compromised slope
  • Poor drainage due to clogged scuppers, gutters, and downspouts or due to defective interior drains
  • Damaged roofing membranes or shingles which allow water to penetrate and reach wooden structures

What to Look For

How to Prevent Roof Rot

By simply following these preventative measures, you can prevent roof rot and avoid serious roof rot-related problems that lead to extensive and costly repairs:

  • Make sure that the attic remains at a moderate temperature year-round to prevent a build-up of moisture, particularly in the summer and winter. Ideal humidity levels are between 40% and 60% — higher levels can cause roof rot to occur.
  • Arrange for a professional roof inspection at least once a year. (Twice a year is preferable for a flat commercial roof.) This is an important preventative measure that can identify potential problems before roof rot has a chance to start.
  • Install a good roof ventilation system (ridge vents, soffit vents or attic fans). The importance of good ventilation can’t be stressed enough in preventing roof rot.
  • Remove roof debris immediately. Debris such as branches and leaves may seem like a minor thing, but they can prevent water from flowing properly off your roof and cause it to back up and pond or get under shingles.
  • Repair cracked or damaged membrane or shingles, replace missing shingles, and replace damaged caulking around chimneys and vents as soon as possible.

What to do if You Spot Signs of Roof Rot

Contact a professional roofing company to have the damage assessed as soon as possible. Before they repair damage, you must address the cause of the roof rot, since it doesn’t make sense to repair damaged areas only to have to problem recur. Don’t procrastinate since the more extensive the damage, the greater the chance that the entire roof will need replacing. Even more serious, the problem can spread to wood components in the building or home itself, which means more than just a roof problem!

If you’re the owner of a commercial building with a flat roof that has experienced ponding or drainage issues, there’s a patented product that can help. RoofSlope is a cost-effective solution for improving drainage on flat cap-sheet roofs by providing improved sloping. It won’t damage the integrity of existing cap-sheet installation. It’s relatively easy to apply, is UV-stable, durable, and provides a superior bond over multiple substrates. It’s also fast-drying — RoofSlope is fully cured just 24 hours after application. Contact us to learn more about this revolutionary solution to water problems on flat roofs, and to find a distributor in your area.


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