Where to look for mold in a building attic - how to find visible attic mold, hard to see mold, or hidden attic mold
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This document gives advice on how and where to inspect or test for mold in building attics and roof cavities. This is a chapter of
"How to Look for Mold" which describes how to find mold and test for mold in buildings, including how and where to collect mold samples using adhesive tape - an easy,
inexpensive, low-tech but very effective mold testing method. (See MOLD TEST KITS for DIY MOLD TESTS for details).
Readers of this article series about black, white, green and other colored mold on attic and under-roof surfaces should also be sure to read ATTIC MOLD CAUSES and also see INSULATION MOLD where we discuss the risk of non-visible problematic mold hidden in building insulation.
WHERE TO LOOK FOR ATTIC MOLD - Places to look for attic mold
This brown mold on plywood roof sheathing visible in an attic is an indicator of wet or damp attic
conditions. It is common to identify Cladosporium sphaerospermum or perhaps Aureobasidium pullulans
in these conditions, though without a lab test we don't know what this mold is. (Click photo for larger image).
The black staining on the plywood roof sheathing visible in this modern attic is a clear indicator of very
humid or even wet attic conditions.
When you view the larger copy of this image (click photo for larger image)
you may notice that insulation was pushed out into the building eaves where it blocked any intake venting. This
black staining is probably mold.
Though we can't assert that this mold is harmful, we can conclude that the
attic has been too wet and that roof venting is not working on this building.
Inspect attic insulation, insulation kraft paper facing, and the attic side of ceiling drywall visible in
the attic floor, particularly in areas below roof leaks. It is useful to distinguish between a real roof leak
or ice dam leak and more trivial drip stains from attic condensation.
Attic condensation and the resulting
drip marks on the attic floor or on attic insulation, as shown here, is not itself likely to wet the attic
insulation nor the surfaces below it enough to cause a big mold reservoir. However, attic condensation is evidence
of wet or very humid attic conditions. Therefore I'd take a close look at the roof sheathing and framing
If attic insulation has been wet and especially if the insulation has been exposed to other moldy conditions, even
if the insulation itself looks ok it may be mold contaminated.
Some types of building insulation readily harbor mold
contamination even if it's not visible (such as fiberglass insulation). Other types of insulation such as cellulose,
seem to resist mold growth (possibly because that material is usually treated with a fire retardant chemical which may also be fungicidal.)
The drip spots you see on attic flooring and insulation in this photo are from attic condensation which
formed on protruding roof shingle nails in the attic where it formed frost in cold weather, then melted
and dripped onto the attic floor.
This indicates poor attic venting and possibly humid conditions. But there
probably was not enough leakage to cause a mold infection of the insulation or drywall below.
Spot checks for
visible mold in the most-likely or most-dripped-on area may be all that's needed.
Look for mold around roof leak areas & water stains in the attic: at the eaves where shingles are more worn or where ice dam
leaks may occur in freezing weather, at roof penetrations for chimneys and
plumbing vents
Attic or Under-roof Condensation Drip Marks: Some "leak stains" you may see on the attic floor or on insulation are
not really due to leaks from above. You may be looking at more trivial drip stains from attic condensation.
Attic condensation and the resulting
drip marks on the attic floor or on attic insulation, as shown here, is not itself likely to wet the attic
insulation nor the surfaces below it enough to cause a big mold reservoir. However, attic condensation is evidence
of wet or very humid attic conditions.
Therefore take a close look at the roof sheathing and framing
in an attic that has been moist or humid even if there have been no roof leaks.
The mold shown in the attic photographed here was identified as Aspergillus sp. on
attic mold visible on pine tongue and groove roof sheathing near the building eaves.
Also notice the condensation stains at the shingle nail, more evidence of a history of attic moisture which was a factor in this mold growth. (Click photo for larger image).
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