Attic Mold
Attic mold is a ventilation failure, not a roof leak, about eighty percent of the time. Warm moist air leaks up from the living space, hits the cold underside of the roof deck in winter, condenses, and feeds growth on the sheathing. It shows up as dark staining on the plywood, usually worst near the eaves.
Signs to look for
- Dark or black staining on the underside of the roof deck
- Frost or water droplets on nails in winter
- Damp or matted insulation
- A musty smell when the attic hatch is opened
- Ice dams forming at the eaves
What usually causes it
- Bathroom or kitchen fans venting into the attic instead of outside
- Blocked soffit vents, often from insulation
- Insufficient ridge or gable ventilation
- Air leaks around recessed lights and the attic hatch
- Actual roof leaks, which are the minority of cases
Removing the growth without eliminating the water source simply resets the clock. Every report we write identifies the moisture source, because that is the finding that determines what it actually costs you to fix.
How we investigate it
Locate the moisture
Thermal imaging and moisture meters map the full extent of wet material, including behind finishes.
Establish the source
Groundwater, plumbing, condensation and ventilation failures all look similar at the surface and need completely different fixes.
Sample if it changes the plan
Air sampling with an outdoor control where growth is hidden; surface sampling where it is visible.
Document and hand off
A written report you can hand to a contractor, an insurer or a landlord — and independent clearance testing afterwards.
Related
Common questions
What causes attic mold?
Bathroom or kitchen fans venting into the attic instead of outside; Blocked soffit vents, often from insulation; Insufficient ridge or gable ventilation.
How do I know if I have attic mold?
Dark or black staining on the underside of the roof deck; Frost or water droplets on nails in winter; Damp or matted insulation.
Can I clean it myself?
Under roughly ten square feet with a known, corrected water source, most homeowners can clean it safely with gloves, an N95 and good ventilation. Above that, or where HVAC is involved, where the water was contaminated, or where someone in the household is immunocompromised, containment matters because disturbing growth spreads it through the building.
Will it come back after cleaning?
Yes, if the water source is still there. This is the single most common reason people call us twice. Cleaning removes what has grown; only correcting the moisture stops it regrowing.
Do I need a lab test for this?
Not always. If growth is visible and the cause is obvious, a laboratory result rarely changes what you should do. Testing earns its cost when the source is hidden, when documentation is needed, or when you want to verify a remediation job.
Get a straight answer about your building
We test, document and verify. We never sell remediation, so we have no reason to find a problem you do not have.