High indoor humidity is not only an inconvenience (since it makes everything feel sweaty and sticky) but also a problem that needs to be fixed as soon as possible. That’s because left unattended, excess indoor humidity can cause several roofing issues.

Why Excess Indoor Humidity Is a Problem

What are the roofing issues caused by excess indoor humidity?


Mold thrives in a damp environment created by excess moisture. Warning signs of mold are musty smells, dark-colored spots on the walls (mold comes in all kinds of colors), and allergy flare-ups (mold spores can aggravate respiratory conditions). Aside from being a health risk, mold also poses a threat to your roof since it can damage the wooden beams that form its structural support.

If you notice any of the early warning signs of mold, it’s important to contact a professional roofer as soon as possible. That’s because mold can easily affect other parts of your home if damaged roofing components aren’t replaced immediately.

Dry Rot

The term dry rot is a bit of a misnomer since this type of fungus needs moisture to grow. (To be specific, it needs wood to have a moisture content of more than 20%). In the early stages, dry rot looks a lot like the surface of a mushroom cap with purplish and grayish hues. But in its later stages, it starts to resemble cotton wool.

Why is dry rot a problem? This fungus breaks down cellulose and hemicellulose in wood (two compounds that give wood its characteristic rigidity) and turns it brittle, causing structural damage to your roof.

How to Keep Indoor Humidity Under Control

An adequate ventilation system helps prevent the formation of mold and dry rot and protects your residential roofing system from other moisture issues. As a general rule, there should be a square foot of net free area (NFA)—the area through which air can pass—every 300 square feet of floor area for attics with a vapor barrier. If you’re not sure if your roof and attic have enough air vents, it’s best to consult one of your local roofers.

Looking for roofers near you?

Kingdom Roofing offers professional residential and commercial roofing services. To get a free inspection and estimate, call us at (941) 217-2411 or fill out this form.