Crawlspace Mold: How to Find, Test, & Prevent Mold in Crawl Spaces InspectAPedia® -
How to find, test, prevent, or remove mold from building crawl spaces
Questions & answers about the cause, health hazards, clean-up, and prevention of mold in building crawl spaces
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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This article is part of our series:
FIND MOLD in buildings, HOW TO 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).
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. If your crawl area or basement has a dirt surface, see MOLD ON DIRT FLOORS.
Readers should also see ATTIC MOLD, see BASEMENT MOLD, and BASEMENT MOLD WATER IMPACT.
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.
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:
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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
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
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
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
Allergen Tests in buildings advice about how to test, what to look for, in evaluating the level of dog, cat, or other animal allergens in a building
"IgG Food Allergy Testing by ELISA/EIA, What do they really tell us?" Sheryl B. Miller, MT (ASCP), PhD, Clinical Laboratory Director, Bastyr University Natural Health Clinic - ELISA testing accuracy: Here is an example of Miller's critique of ELISA
http://www.betterhealthusa.com/public/282.cfm - Townsend Letter for Doctors and Patients
The critique included in that article raises compelling questions about IgG testing assays, which prompts our interest in actually screening for the presence of high levels of particles that could carry allergens - dog dander or cat dander in the case at hand.
http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html contains similar criticism in another venue but interestingly by the same author, Sheryl Miller. Sheryl Miller, MT (ASCP), PhD, is an Immunologist and Associate Professor of Basic and Medical Sciences at Bastyr University in Bothell, Washington. She is also the Laboratory Director of the Bastyr Natural Health Clinic Laboratory.
Allergens: Testing for the level of exposure to animal allergens is discussed at http://www.animalhealthchannel.com/animalallergy/diagnosis.shtml (lab animal exposure study is interesting because it involves a higher exposure level in some cases
Allergens: WebMD discusses allergy tests for humans at webmd.com/allergies/allergy-tests
Animal Allergens: Dog, Cat, and Other Animal Dander - Cleanup & Prevention Information for Asthmatics and regarding Indoor Air Quality.
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
Rodent control issues, including dander, fecal, and urine contamination of buildings and Building insulation are discussed at our
Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon)
Atlas of Indoor Mold, Online Clinical Mold Atlas, Toxins, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
Black Mold that is Harmless Photos of recognizable, usually harmless black mold on wood, bluestain, ceratocystis, ophistoma
Building Floods: quick steps after a building flood or plumbing leak can prevent costly mold contamination
Classes of Mold: what types of cosmetic, allergenic, or toxic mold are a problem? Can mold be cleaned-up successfully?
"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
"Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
"Disease Prevention in Home Vegetable Gardens,"
Patricia Donald,
Department of Plant Microbiology and Pathology,
Lewis Jett
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
OTHER IAQ ISSUES: How To Find and Address Other Indoor Air or Indoor Environment Contaminants Besides Mold
Mold or allergens may not be the only or even the main indoor environmental contaminant. Don't let media attention to mold
cause so much enviro-scare fear that other, possibly more urgent hazards go un-addressed.
Ozone Warnings - Use of Ozone as a "mold"
remedy is ineffective and may be dangerous.
Pet control - if you can't say goodbye to your bird, cat, dog, guinea pig, hamster, tropical fish, then limit the
areas they occupy and limit the airflow from that area to sleeping or other areas of the building, use allergenic
bedding, eliminate wall-to-wall carpeting, improve housecleaning including use of a HEPA-rated vacuum cleaner. For more details
see our article Dog, Cat, and Other Animal Dander - Information for Asthmatics and Indoor Air Quality
Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings,
and high levels of these materials in building insulation in those locations. If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating
the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing
rodent problem. If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some
help from a licensed pest control expert.
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