Attic mold looks like a roof leak problem and usually is not one. The typical presentation is dark staining on the underside of the roof sheathing, heaviest on the north facing plane and worst near the eaves, spread evenly rather than concentrated at one point. A roof leak produces a localised stain that follows a path. Even distribution across a whole plane is condensation, and condensation in an attic means warm moist air from the house is getting up there and meeting a cold surface.
The mechanisms are consistent. Bathroom and dryer exhaust ducts terminating in the attic instead of through the roof or a gable, which is a common defect in this housing stock and dumps a shower's worth of moisture into the attic several times a day. Air leakage through recessed light housings, plumbing penetrations, the attic hatch and top plates, which carries humid indoor air upward all winter. And insufficient ventilation, where soffit vents have been blocked by insulation and the ridge vent has nothing to draw from.
Winter is when it happens. Warm moist air rises into a cold attic, condenses on the sheathing which is the coldest surface up there, and the moisture sits in the wood long enough for growth to establish. By spring it is visible and by the second winter it is significant. North facing planes stay coldest and go first.
Remediation is containment, removal of affected insulation, and treatment of the sheathing, usually by sanding or media blasting where growth has penetrated the surface fibres. But the remediation is the smaller half. Unless the exhaust ducts are routed outside, the ceiling plane is air sealed, and the soffit to ridge ventilation path actually works, the growth returns within two winters. We will not do the removal without addressing that, because it wastes your money.
Technician insight
Count the bathroom fans, then count the roof or gable terminations. If those two numbers do not match, you have found the cause before opening a single tool case. A duct discharging into the attic is behind most of the attic mold we remediate in this county.
Attic Mold Removal Services We Offer
✓Roof Sheathing Mold Treatment
Sanding or media blasting where growth has penetrated the surface of the plywood or OSB.
✓Exhaust Duct Correction
Identifying ducts terminating in the attic, which is the single most common cause we find.
✓Air Sealing Assessment
Locating the leakage paths carrying humid indoor air into the attic through the ceiling plane.
✓Ventilation Path Review
Checking that soffit intake is not blocked and that the ridge vent has an actual airflow path.
How it works
- 1
Diagnose the moisture
Distribution pattern, duct terminations, air leakage and ventilation assessed before anything else.
- 2
Contain
Barriers and negative air at the attic access so spores do not come down into the house.
- 3
Remove and treat
Affected insulation out, sheathing sanded or blasted and treated.
- 4
Correct the cause
Ducts rerouted, ceiling plane sealed, ventilation path restored. Without this it comes back.