White Mold on an interior door Pictures of White Mold in the Home
a Photo Library for detection and identification of white mold contamination in buildings

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White building mold identification photographs: how to recongize white fungal mold growth.

What does white mold look like on building surfaces and how hard is this mold to see? Photos of white, gray, & light-colored mold in buildings - how to find & recognize mold on building surfaces.

These photos of mold on indoor building surfaces may help you recognize mold in buildings, recognize probably-cosmetic mold, and recognize stuff that is not mold and does not need to be tested.

Photographs of light colored mold & other molds of various colors and textures in buildings. Special methods needed to spot white & light colored mold growth indoors

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Photographs Help Identify Mold in Buildings

White and brown basement mold (C) D FriedmanWhat white or light colored mold looks like in a home or in or on other buildings & building surfaces.

These mold samples and mold spores and their photographs and examples of materials sometimes mistaken for mold have been collected in the U.S., Spain, Mexico, France, as well as in other countries where I've studied bioaerosols.

[Click to enlarge any image]

For photos and an explanation of white fluffy stuff or white crystalline material often found on building walls, especially on masonry surfaces, but that is not mold,

Also see the white or light colored mold discussed at MILDEW in BUILDINGS ?.

A great many white and light-colored grayish molds can be easily seen on building surfaces, especially on the exposed or inner wall-cavity side of drywall in buildings that have been exposed to wet or flooding. Some of these white or very light gray molds include members of the Aspergillus or Penicillium genera as well as some basidiomycetes.

Our white building mold photo at above-left illustrates that other white molds in found in buildings may be the mycelia (think "root hairs") of many different genera/species of fungi that at their fruiting bodies will be seen in other colors and textures.

But most white building molds cannot be reliably identified to genera/species without microscopic analysis by a qualified aerobiologist/microscopist in a test lab.

Article Contents

Identification Photographs of White & Light-Colored Mold Growth in Buildings

White mold on subflooring (C) Daniel Friedman

Here are photographs of both obvious white mold & fungal growth in buildings and also more difficult to see white or light gray mold growth on building surfaces. Above we show white mold growth on tongue and groove subflooring in an older home in the northeastern U.S.

Below we see extensive white fungal growth (white mold growth) on OSB subflooring and on a floor joist over a wet crawl space in New York.

When you see a white "fungus" or "mushroom" like structure you're seeing the fruiting body of some mold species. Other white or light colored moulds in buildings appear as tiny white spots, even as white or gray or light-green "dust" as you'll see in our photographs in this article.

White mold on wet OSB subflooring over a crawl area (C) Daniel Friedman

Light colored molds, depending on the genera species, may be more of a health risk than the infamous "toxic black mold" that people look for in buildings.

Fungal groups such as Penicillium sp. and Aspergillus sp. produce species in a wide range of colors, some of which can be quite light in color and difficult to spot on building surfaces, but these molds may produce small, easily-airborne toxic or pathogenic mold spores that present a health risk to building occupants.

White stuff that is not mold: Beware: many people mistake mineral salts or efflorescence for white mold. Efflorescence is a white crystalline salt left on masonry surfaces where water or moisture have been evaporating.
See STUFF THAT IS NOT MOLD for photos of white fluffy material or white crystalline material that is often mistaken for mold.

Above we show white mold on wood subflooring and on OSB subflooring in a wet crawl space. Below we show additional photos of white and light colored molds found in buildings.

Light colored mold on an interior door in a damp basement

The white mold growing on this basement door was hard to spot without careful use of lighting. It looks almost like white dust, but unlike settled dust, a closer look at the mold-suspect surface will show growth patterns of the fungus and a relationship between the mold location and moisture or water exposure. Dust tends to be more uniform over a specific building surface.

Be sure to review our article on LIGHT AIM FINDS MOLD.

Example of using light to see white mold on paneling

The white mold growing on this basement stairwell paneling was impossible to see until we directed our flashlight across the surface.

Read LIGHT, FLASHLIGHT for MOLD - proper use of a flashlight can help spot mold on paneling and other building surfaces. Also see how LIGHT AIM FINDS MOLD.

White mold in an attic on the roof sheathing

Here is a photograph of white mold that was very easy to see (and possibly some light-green mold) on yellow pine tongue and groove roof sheathing visible in the attic of an older home in the Northeastern United States.

Fungus growth on resilient bathroom floor (C) D Friedman GP

White mold that turns brown: Stemonitis sp.

Here is a photograph of a white fungus found growing on resilient flooring in an Australian bathroom. This fungus was very easy to see but was for a time a bit curious.

Covered and kept moist for just a brief interval, this Stemonitis sp. matured into an easily recognizable form of brown slime mold that we illustrate and discuss at Rental Apartment Mold Safety Advice and also in more detail at BROWN HAIRY BATHROOM MOLD

White Mold Growth on the Interior Surface of Fiberglass-lined HVAC Ducts

White deposits on fiberglass HVAC Duct interior (C) JC

[Click to enlarge any image]

Above: white "growth" found on the interior surface of fiberglass-lined HVAC ducts in a home in Atlanta, GA in 2016. Look closely to see the presence of clear adhesive tape being used to collect a sample from this surface to permit laboratory analyais.

Samples from this fiberglass duct were examined in our forensic laboratory.

Below: an example of lab test results included these:

Fiberglass duct  surface mold test results (C) Daniel Friedman Fiberglass duct  surface mold test results (C) Daniel Friedman

Above first photo, sample 2, Aspergillus sp. conidiophore (photo center) and hyphae at upper left corner of the image. Above second photo sample 2, Cladorporium sp. in dense fungal growth on the surface. Details of this air duct mold contamination study based on clear adhesive tape samples of the mold-suspect surface of the air duct are found at FIBERGLASS AIR DUCT MOLD TEST.


White Mushroom-like Fungus Growing In Insulated Crawl Space Wall Cavity

White fungus growth in buiding wall cavity (C) InspectApedia RM

Question: is this white stuff effloresence or mold?

Hi, while cleaning out the 4 foot crawlspace of my split level house I noticed a black patch a foot long on the drywall. Decided to remove it and look behind. Found a white crystal-like substance on all the 2x4s. In one spot it looks like it is growing away from the 2x4 onto the vapor barrier in a oyster shell shape.

Crawl space wall leaks invite mold growth (C) InspectApedia RM Crawl space wall leaks invite mold growth (C) InspectApedia RM

This is an outside wall, insulated with fiberglass and covered in drywall. It also is where the water pipe is located for the outside use. The lower right corner has a lot of dark patches on the wood. We've owned 10 years and never had any water leak. Any way I can attach or send a photo? Thank you.

White fungus growth in buiding wall cavity (C) InspectApedia RM White fungus growth in buiding wall cavity (C) InspectApedia RM

Here [are more photographs] of the white stuff on the 2x4s in my insulated crawlspace. This is a horizontal 2x4 at head height (ceiling of crawlspace which is under floor for the living room on top). It has rather thick white growth as well as branches reaching out making contact with the vapor barrier.

I can see that all 2x4s within a 4ft area have this. Suspect condensation from copper pipe leading through here to exterior has created sustained dampness. House built in 1995.

Thanks for identifying the white stuff, if at all possible. I want to see if it's safe for me to remove all remaining drywall, vapor barrier and insulation in order to find the issue, and clean the area. I'm hesitant to let the white stuff "breathe" out in the air without knowing for sure what it is. The only local mold expert said in 40 yrs never seen white stuff I am describing, so he said no use he comes out. - Anonymous by private email 2016/11/09

This question appeared originally at MOLD APPEARANCE - STUFF THAT IS NOT MOLD

Reply: what to do about mushrooms growing in a building wall

Those photos look like white mushrooms growing in your wall, on wood surfaces. That's not effloresence.

Typically basidiomycetes or wood-rotting fungi grown on wet wood and can appear rather quickly even indoors in wet conditions, so I cannot guess from the white fungus how long this problem has been going on. These fungal fruiting bodies may appear in any of many colours, commonly brown, white, red, even blue or very dark, almost black. More examples of mushrooms growing in or on buildings are
at MOLD on DIRT FLOORS - separate article, includes white mold on dirt in crawl spaces & basements

When you can I'd like to see also a couple of more-distant shots of the wall to see the situation as well as to see photos of the same sides of the building from outdoors.

You should

  1. Investigate further: Expect there to be other mold present, both visually obvious and not. The wet conditions that caused this fungal growth are likely to also have invited other mold genera species that do not produce large white basidiomycete fruiting bodies which is what your photos seem to display. [I'd like to see photos of the material when the plastic is removed.] You should also inspect and probe the wood structure for rot.
    More help is at HIDDEN MOLD, HOW TO FIND
  2. Remove the mold and fungal growth: Plan to remove all visibly moldy material such as insulation. You can reduce personal risks by wearing protective clothing, a HEPA respirator, goggles, etc., and you can reduce the chances of blowing moldy dust into the upper, occupied part of your building by creating negative air pressure in the crawl space - a professional would seal off the area and install one or more air handlers or fans blowing "out" of the crawl space.
    More help is

    I do not think you need to "test" for mold when a fungus is plainly visible.
  3. Remove other moldy materials that cannot be cleaned: Remove any nearby insulation and any insulation that was wet, to a stud bay or 18" space of clear un-contaminated, dry, clean insulation or material.

    Watch out: be alert for discovery of a large area of mold contamination. If you find more than 30 square feet of visibly contiguous mold growth then it's probably time to hire a professional.
  4. Clean and dry the area: Clean the exposed cavity and let it dry before re-insulating and restoring the wall.
  5. Re-Insulate & repair damage: in my opinion, using fiberglass insulation below ground in an area likely to be wet or exposed to high humidity invites mold problems in the future. I'd consider a closed-cell foam insulation as an alternative.
  6. Fix the cause of mold growth: Find and fix the source of water entry so that it doesn't recur. I suspect that there has been water entry into your wall or crawl space.


Continue reading at MOLD APPEARANCE - WHAT MOLD LOOKS LIKE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see EFFLORESCENCE SALTS & WHITE DEPOSITS - for examples of moisture-related white deposits that are not mold.

Or see HUMIDITY CONTROL & TARGETS INDOORS for an example of white mould occurring in a U.K. home with venting & humidity questions.

Or see LIGHT AIM FINDS MOLD - how to use your flashlight successfully

Or see LIGHT COLORED MOLD - more light coloured moulds besides white can be hard to spot

Or see LIGHT, FLASHLIGHT for MOLD - proper lighting shows up hard-to-spot mold

Or see MOLD APPEARANCE - WHAT MOLD LOOKS LIKE - a Photo ID Library for detection and identification of mold allergens on indoor building surfaces.



Or see WHY DOES MOLD GROW in INSULATION? that includes photos and test results examining suspected mold on the surface of fiberglass-lined HVAC ductwork.

Suggested citation for this web page

WHITE MOLD PHOTOS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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