Roof Sheathing Mold

Mold growth on attic roof sheathing is a common issue in cool climates such as the pacific northwest.

Roof sheathing mold.

Attic spaces are one of the most common places in a home for mold to be found growing. Increasingly homeowners in the pacific northwest are noticing mold on the underside of their roof sheathing. What caused the mold and why did it thrive in this attic space. One puzzling aspect of the phenomenon is that the mold is found in well built homes that comply with all relevant building codes.

Mold that grows on the underside of roof sheathing due to ideal mold growth conditions being present. This phenomenon occurs in vented attics and is more common in new homes than old homes. Mold growth provided it is not just cosmetic mold which can simply be left alone can be cleaned from wood surfaces by blasting scrubbing or even simple surface wiping depending on the surface accessibility and smoothness. The insulation was improperly installed over the soffit vents blocking air from entering the attic.

This occurs when the temperature of the sheathing drops below the dew point creating a thin layer of moisture on the substrate. In the vast majority of cases the mold growth is caused by condensation. Mold on the underside of roof sheathing is also very common. The presence of mold in your attic is often the result of poor ventilation insufficient insulation moisture from a roof leak or improper venting from your bathrooms or kitchen.

Because wood is porous it may be difficult to remove the mold stains from sheathing but you can kill the mold by cleaning the sheathing with bleach and water.