Photograph: toxic mold on pine tongue and groove roof sheathing - © Daniel Friedman What does mold in attics look like?
Which attic molds are likely to be harmful?

  • ATTIC MOLD, WHAT IT LOOKS LIKE - CONTENTS: What does attic mold look like? Appearance of roof mold. Examples of white attic mold, green attic mold, brown attic mold, and black attic mold. Where to look for mold in a building attic.
  • POST a QUESTION or READ FAQs about how to spot mold contamination in building attics: what does attic mold contamination look like?
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Appearance of attic mold contamination:

This document gives advice on how to find, test for, and remove attic mold. Here we show what mold looks like in building attics with mold photographs.

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.

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WHAT ATTIC MOLD LOOKS LIKE - What does attic mold look like?

Photograph: toxic mold on pine tongue and groove roof sheathing - © Daniel Friedman

White attic mold: The photo at page top shows white attic mold on the roof sheathing and rafters and some brown or black mold on the attic-side of ceiling drywall where we pulled back insulation.

Green attic mold: In the attic photograph at left we show a mix of green, gray, and white attic mold. When looking for attic mold, trace both leak areas and areas of poor ventilation in the attic.

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 in an attic that has been moist or humid even though there were no roof leaks. (Click photo for larger image).

The mold shown in the attic photographed aove 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).

Photograph of extensive brown mold contamination of roof plywood in an attic
Daniel Friedman 04-11-01

Uncertain attic mold: The photo at the very top of this page shows where you may find mold growing on the attic side of ceiling drywall, particularly below roof leaks or in areas of ice dam leaks at a building eaves.

Brown mold on plywood roof sheathing in an exposed to leaks or moisture problems is one of the most common molds spotted by home inspectors.

Often in attics we also find Cladosporium sphaerospermum or Aureobasidium pullulans which looks about the same, or a little darker on plywood or framing.)

When the attic has been damp or wet, there might be a more serious problem with Aspergillus sp. or Penicillium sp. in mold contaminated-insulation.

Photograph of extensive brown mold contamination of roof plywood in an attic
Daniel Friedman 04-11-01

"Black mold" in attics: in this photo of very dark mold in an attic, in a wet attic mold which we found to be "brown" in the microscope, looked "black" on the plywood.

The black attic mold shown here confirms that this attic had a serious venting and moisture problem, including moisture from sources lower in the building.

The insulation was contaminated, and we inspected the attic side of the ceiling drywall below for signs of leak stains or mold.

This article is part of our series: MOLD in BUILDINGS 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 TEST KITS for DUST, MOLD, PARTICLE TESTS for details). This procedure helps identify the presence of or locate the probable sources of mold reservoirs in buildings, and helps decide which of these need more invasive, exhaustive inspection and testing.

Reader Question: once attic ventilation is improved do I need to remove attic mold?

(Mar 5, 2012) Paul said:

I appreciate the article and information. So if this type of "black mold" shown in the second picture ( described as Cladosporium sphaerospermum or Aureobasidium pullulans which looks about the same, or a little darker on plywood or framing) is due to moisture/circulation problems ( in this case, insulation was packed where baffles should have been placed) what needs to be done if anything at all. Is the condition harmless?

Once baffles have been installed to promote circulation, is the problem solved and no further action required? I eventually will add a doghouse/false dormer and change the roof line on another section of the existing roof. I was planning to have the sheathing replaced in a few months. Will the replacement of the sheathing create any problems? Thanks once again for sharing your information and expertise



First: any mold growth is a water or moisture indicator which means there may be other mold or water related problems that would be a concern but were less visually obvious - so some investigating is worthwhile.

Second we can't identify mold in-situ - it takes a lab analysis; there are about 1.5 million species, (happily they don't all grow indoors) but plenty look alike on building surfaces.

Third: even the king of molds (Cladosporium sp.) includes species that are allergenic - properties can be a problem for some people with allergies or asthma, or that can cause illnesses. The actual risk depends on the quantity, location, the exposure as well as individual sensitivity.

Watch out: also for mold-contaminated building insulation in attics (or other building cavities) where there have been leaks or high moisture levels.

Certainly if you're going to do a tear-off of moldy sheathing (don't do that just because of mold) it's not worth any costly testing, but it would be worth protecting the building interior and insulation from all that moldy dust and debris - or just pull out old inulation, clean the exposed surfaces (HEPA Vac is fine if there's no growing mold to be cleaned off), and re-insulate.

Reader Question: is green attic mold harmful

(Mar 3, 2013) DD said:
I just found green mold in the attic?



Watch out: while a lab test would be needed to reliably identify the genera/species of the green attic mold you have found, a common greenish-coloured mold found in attics and roof spaces on wood surfaces includes several species of Aspergillus sp. that could be harmful, particularly if it is entering the living area.


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