Crawlspace Mold: How to Find, Test, & Prevent Mold in Crawl Spaces
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This article explains how to find and deal with mold in building crawl spaces. We explain how to spot crawl space mold contamination, when mold testing is appropriate, the risk of mold-contaminated crawl space insulation, the causes of crawl space mold, and how to clean or remove crawl space mold as well as how to prevent moldy crawl spaces in the first place.
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CRAWLSPACE MOLD: finding the problem mold, allergens, or other particles in crawl spaces
This crawl space inspection procedure for mold 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
The photograph at page top shows extensive fungal growth on the underside of subflooring and on wood framing supporting a wood floor over a very damp
crawl space. Depending on the mold genera/species, if an airborne fungus is present at high levels in a crawl space, spores of that mold
may move easily to upper levels in the building.
We very often find that insulation in crawl spaces has become a problem mold reservoir. Some of these molds move easily from the crawl area up into the living space.
For example, Penicillium sp. or Aspergillus sp. spores, which can be as
small as about one micron in diameter, are so tiny and light that they can move much like a gas in a building.
These tiny spores rise
in upwards-moving air currents as warm air, rising to upper building levels, creates a slightly lower air pressure in lower building
areas such as basements and crawl spaces.
Depending on the tightness of construction, and the presence or absence of hot air or central
air conditioning systems which themselves may increase indoor air particle movement, the rate of movement of particles from a moldy
crawl space can vary widely.
In some instances we have found rather high levels of airborne mold spores and mold spores in settled dust
that tracked directly to the moldy crawl space.
In other instances we found that there was not much air and particle movement upwards from
a crawl space or basement, until specific triggering conditions occurred.
These included opening of a basement door, or in the case of crawl spaces,
opening upper floor windows or turning on a whole house exhaust fan. These conditions led to a significant increase in movement of
crawl space (or basement) mold from lower building areas into the living space.
First aid for moldy crawl spaces - what to do about mold in a crawl space
- Do not enter or work in a moldy area without wearing proper respiratory and other personal protection. See CRAWL SPACE SAFETY ADVICE
- Evaluate the history of water entry, dampness, ventilation, listing the factors conducive to fungal growth such as:
- Present or past wet conditions, whether "once", episodic, or recurrent water entry
- Marginal or no ventilation. Actually I prefer to stop trying to vent crawl spaces since when we want venting it's usually inadequate, and depending on weather conditions venting a crawl space can actually increase its moisture level and make matters worse. A preferred approach is to dry out, enclose, and seal a crawl space under a building, making it into conditioned space.
- Exposed dirt. If the crawl space has a dirt floor, put down 6-mil plastic over the dirt to reduce moisture movement from the soil into the crawl space. Also see MOLD ON DIRT FLOORS
- Presence of fiberglass or other fibrous insulation
- Fix outside conditions that are causing wet crawl space conditions such as roof gutter or downspout spillage by the building foundation.
- Fix inside conditions that wet crawl spaces, such as plumbing leaks or improper ventilation.
- Look for visible mold:
- Inspect the exposed sides of all framing, joists, girders, posts
- Inspect the exposed under-side of subflooring of the floor overhead. See our warning about mold growth on pine boards discussed at Attic inspections above.
- Special screening tests may assist in evaluating the condition in inaccessible crawl spaces.
- See HOW TO LOOK FOR MOLD and HIDDEN MOLD, HOW TO FIND
- Prevent mold movement into the living area: As with a moldy basement, keep openings between the crawl space and living space closed as much as possible.
- Remove wet or mold-suspect insulation.
- Test representative samples of mold before going to a major expense to be sure you're not just looking at cosmetic mold on framing lumber,
or at something else that is not even mold.
If a large area of visibly moldy material is present (more than 30 sq .ft.) professional cleaning and remediation are probably in order. In
that case, a building inspection and preparation of a mold remediation plan is a good idea - that work should be performed by someone who has
no conflicts of interest - in other words, not by the mold cleanup company or their agent.
Follow any costly mold remediation job
with a clearance inspection and test before you make final payment.
- Review MOLD PREVENTION GUIDE
Correct the Causes of Mold and Prevent Indoor Mold or other indoor environment problems
Risks of Mold Contamination in fiberglass insulation in a crawl space
These photos show crawl space fiberglass which had fallen onto the dirt crawl space floor.
We can pretty much count on this material to be mold contaminated unless the building was in an arid climate.
You can expect to find rodent contamination as well in insulation in this condition.
This photo shows crawl space fiberglass which the installer supported by chicken wire. The crawl space was pretty drafty which we might hope would keep it dry and less moldy.
However we might expect to find a nice mouse colony here, and depending on
weather variations and crawl space flooding, this insulation too is at risk of becoming a mold reservoir.
We'd have preferred to use a solid foam insulation in conditions like this.
Key building water entry diagnosis and cure articles:
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.
Reader Question about Mold in Dirt Crawl Space
Hi I have attached a few pics of the mold growth on my dirt crawl space each pic is isolated and no further spread is seen anywhere else. I was actually shocked to see this strange looking growth. I do keep the crawl vents open but there is no forced air movement at all. Please assist as to how to safely remove.
The house sustained a fire in may of 2014 and the ac system has been off since. There are fans running in house though. The only power to crawl space is to the sump pumps that discharge any water to the outside via pipes which none of the pics of the mold spores / mushrooms are even close to the sump liners of perimeter pipe in perimeter ditch.
There is no black plastic liner on dirt floor and no floor joist insulation, I removed all several years back when I dug my perimeter ditch and sump pits with the plastic liners. Thanks for any guidance! - G.E. 9/8/2014
Nice photos - that blue fungus is not one I've seen before. I've posted all of your photos also at MOLD on DIRT FLOORS.
Most likely these grow where you see them because of a combination of moisture and organic material spilled on or in the soil.
Certainly you describe a damp or wet crawl area and one that was previously flooded (during fire extinguishment) - all of which invite fungal growth therein.
You can dig out (just an inch or so) the visible mold, toss it into the woods or into garbage, then put down plastic, and take other steps to dry out the area.
Probably more important would be mold growth on the exposed wood framing or in insulation if there is some in the crawl area. For that topic
see INSULATION MOLD TEST
or for more about the development of mold in fiberglass insulation see FIBERGLASS INSULATION MOLD
See CRAWL SPACE DRYOUT - live link just below - for procedures to prevent further mold problems in the crawl area.
Continue reading at CRAWL SPACE DRYOUT or select a topic from the More Reading links shown below.
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CRAWLSPACE MOLD ADVICE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.
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Technical Reviewers & References
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- Recognizing Mold: What mold looks like mold identification photos to help identify mold - choosing what to sample in buildings
- Recognizing Allergens: What various indoor allergens look like - identification photos to help identify pollen, dust mites, animal dander, toxic or allergenic mold - Common Mold and other Allergens, Irritants, Remedies & Advice
- Stuff that is not mold but is often mistaken for it - things you may not want to test. Also, not all "black mold" is toxic - here are examples of harmless black mold.
- MOLD ACTION GUIDE an easy step by step outline of what to do about mold
- How to find mold without hiring anyone, for do-it-yourself'ers
- Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
- Mold Test Kits - How to Collect and Send Your Own Mold Sample to our mold testing lab
- How to find a mold inspector or test consultant: Directory of IAQ,Sick Building, Mold Allergen Testing, Building Investigation Service Providers
- Meruliporia: the house eating fungus or "poria"
- Mold Investigation Tips for Home Inspectors how to find mold, where to look, what is likely to be important. Advice to building inspectors intending to inspect or test for toxic or problematic mold indoors, mold inspection methods, and mold test methods which are valid or invalid
- Mold Risk Levels in buildings Based on Visual Inspection - simple visual clues help decide on action
- Mold in Fiberglass Insulation© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation - DJF
- MOLD FAQ's -- check this FAQ list & IAQ Site Map to see if you can find a quick answer to your mold concern
- When to hire a professional to inspect for toxic mold or other allergens
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
- The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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- Environmental Health & Investigation Bibliography - our technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
- Adkins and Adkins Dictionary of Roman Religion discusses Robigus, the Roman god of crop protection and the legendary progenitor of wheat rust fungus.
- Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
- "A Brief Guide to Mold, Moisture, and Your Home",
U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
- US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
- US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol