Case Study 09018: Attic Mold

Facts/History/Observations:

Single family, two story house was converted from a one level ranch originally built in the 1960’s. A recent home inspection discovered mold on the underside of both sides of the roof, mainly on plywood sheathing. Mold was also growing on both gable ends. The attic had a functioning ridge and soffit vent system as well as one open gable vent. The second floor bathroom fan was exhausting into a soffit vent. Mold was reportedly present when the current owner purchased the house at which time they added the ridge and soffit vent system with the new roof. The cause of the mold was inadequate ventilation prior to the installation of the ridge and soffit venting system. There were no other signs of water leaks or sources of accumulated moisture.

Mold on plywood roof sheathing

Inspection Strategy:

• Visual inspection
• Moisture readings in wood materials
• Surface tape-lift sample collected from plywood roof sheathing with black mold

Lab Results:

• Mold Identification: Actively growing Cladosporium
• Classification: Cladosporium is a common, environmental mold often found in attics when there is a moisture problem

Recommendations:

It is recommended to have the attic evaluated to confirm that there is adequate ventilation and to discuss insulation, the bathroom vent, the gable vent, and any other factors that can influence mold growth development. Professional mold remediation is necessary to remove the mold growth in the attic; a homeowner or otherwise unskilled person should not do the cleaning because of the risks involved with such a project. Proper containment and decontamination procedures are needed. All insulation should be removed from the floor of the attic. A sealant should be applied to wood materials as the final remediation step in this attic.