Mold On Underside Of Roof Sheathing

Frost buildup on the underside of the roof sheathing in winter.

Mold on underside of roof sheathing. In the vast majority of cases the mold growth is caused by condensation. This occurs when the temperature of the sheathing drops below the dew point creating a thin layer of moisture on the substrate. This phenomenon occurs in vented attics and is more common in new homes than old homes. Generally tearing off a roof and roof sheathing and perhaps roof framing to remove mold would not be sensible nor cost justified.

If your state doesn t allow you to take a sample to send to a lab recommend testing by a certified mold assessor. Mold must be removed from attic sheathing because the spores can cause serious health problems. Attic insulation incorrectly installed and blocking soffit vents on north side of home. When it s cold enough outside water vapor in an attic with improper ventilation can freeze on the underside of your roof.

One puzzling aspect of the phenomenon is that the mold is found in well built homes that comply with all relevant building codes. There s an underlying moisture issue that needs to be resolved because mold requires moisture to grow and spread. Increasingly homeowners in the pacific northwest are noticing mold on the underside of their roof sheathing. After several years of this there may be dark rings around protruding roofing nails and larger dark spots or areas on the roof sheathing and or exterior gable walls.

While this is easy to spot by the time you see it mold may have already begun to grow. Appears due to this incorrect installation mold is forming on the underside of the roof sheathing. 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. Attic mold left unchecked can grow and lead to structural deterioration of attic sheathing and roof structural elements.

Mold growth on attic roof sheathing is a common issue in cool climates such as the pacific northwest. Mold on the underside of roof sheathing is also very common. Mold can form but often it is. 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.