A Home Buyer's Guide to Mold Inspection & Testing

A home buyer's guide to screening a building for mold contamination & hidden mold
How to look for mold in buildings
Where to look, where to collect mold samples
Sampling mistakes to avoid
What mold looks like in different areas or on different surfaces

This article gives advice to home buyers concerned about inspecting and testing for mold in a building to be purchased but where there is not already a known mold problem.This website describes when and how to find mold and test for mold in buildings and how to correct mold problems. Home buyers or home owners who are concerned about mold and who are considering a mold "test" should read the following articles with care:

BUYERS GUIDE - home inspections for mold
MOLD or INDOOR AIR EMERGENCY RESPONSE
MOLD EXPERT, WHEN TO HIRE
MOLD APPEARANCE - WHAT MOLD LOOKS LIKE
MOLD APPEARANCE - STUFF THAT IS NOT MOLD
MOLD TEST REASONS
MOLD TESTING METHOD VALIDITY
MOLD TEST vs. PROBLEM DIAGNOSIS MOLD TESTING SERVICES lists mold testing professionals.
INDOOR AIR QUALITY IMPROVEMENT GUIDE

Also see MOLD TESTING by HOME INSPECTORS? for an opinion-text on the marketing of mold tests as a revenue source for home inspectors. Contact us to suggest content additions or corrections.

Mold Inspection and Testing Advice for Home Buyers

Mold is everywhere. You can't eliminate it. If you could we'd all be in trouble as nothing would ever decay and we'd all be so buried in junk and debris that nothing could grow on the earth. But we don't much like to see mold indoors and certainly not on our walls, ceilings, or furniture.

There we remove it or clean it off. Because there are potential health risks involved, especially for some people, and because there are significant costs involved in large mold remediation projects, home buyers often contact us to ask about testing a home for mold during the home buying process.

A thorough building investigation for problematic mold needs to address hidden mold reservoirs, for which our approach is to complete a detailed inspection and building (leak) history as well as to record occupant observations and complaints.

A low-cost superficial test or superficial "quick look" for problem mold (such as an "air test for mold", a "home test kit for mold" or a "mold culture test") is likely be a waste of money since those approaches to screening a building for mold contamination are unreliable. Certainly if problem mold is visible that's unambiguous. But superficial visual inspections and grab-tests for mold in air or on surfaces, performed without being accompanied by a very thorough building inspection, history taking, and occupant interview, have a high risk of missing important reservoirs of problem mold in a building.

Some "mold inspectors" may charge as much as a true expert to examine your building ($750 to $2000) but in fact may be doing little more than a quick inspection for visible mold and a few superficial tests. This is also an unreliable approach.

Since water and moisture are gating factors for indoor mold contamination I recommend that you start with a thorough inspection of the building for conditions likely to produce a mold problem - leaks, moisture traps, bad ventilation, history of flooding, etc.

Why Can't I Just Collect a Mold Sample and Based on That, Decide if the House We're Buying Has a Mold Problem or Not?

Question: Quick Lab Turnaround on Mold Tests

Dear Lab Director:

We desperately need the results of the mold sample we collected yesterday ASAP. We cannot proceed with the closing process until we have these results, and our house purchase closing is scheduled for Friday. - Worried in Po-Town.

Reply: Don't Decide to Buy or Not Buy a Home Based on a "Mold Test"

Dear Worried:

While most mold test labs and forensic laboratories can provide very fast mold sample analysis - 24-hours or less after a sample is received, a home buyer who is worried about a possible costly mold contamination problem in a building should certainly not be deciding to go ahead with the sale or not simply based on a "mold test".

This is even more true if the mold test or mold sample was collected by someone who is not an expert.

If there is a reason to be worried that there is a significant mold problem in a building, and if you have not had an expert perform a very thorough, visual inspection, even the most technically proficient "test", alone, is unreliable.

A mold test, even a good one, is a screen that might detect evidence of an indoor mold problem.

But absence of evidence of mold in a building is not, unless accompanied by an appropriate, expert, onsite investigation, never evidence of absence of a mold problem.

If you have a particular concern about the building, and regardless of the outcome of the lab work, we recommend that you discuss this with your attorney, your realtor, and your home inspector. Your attorney may recommend that you either delay the closing, or if agreeable to the seller, obtain some estimates to establish a "worst case" guess of possible mold remediation cost and escrow that amount long enough to give yourselves time for an expert assessment.

Does this mean every home should be inspected and tested by an expert to look for mold?

Of course not. At MOLD EXPERT, WHEN TO HIRE we discuss some criteria that help decide if it is appropriate to bring in a mold expert, such as pre-existing evidence of a problem: large areas of visible mold, evidence of or an historical report of building flooding, significant plumbing leaks, or other leaks, etc.

Why to Hire a Good Home Inspector for a Preliminary Check for Mold-Producing Conditions in a Building

If your "mold inspector" is simply going to enter the building, collect a few air, surface, or culture samples, and perhaps report on obvious visible mold in the living space, you're not receiving a very professional nor very reliable service.

An experienced, thorough, detailed, qualified home inspector will be much better at recognizing those (mold-conducive) conditions than a typical "mold inspector" or a typical industrial hygienist who does not know building science and who lacks experience in identifying where and why mold problems occur in buildings.

Home inspection standards, training, and experience teach inspectors where water, leaks, and moisture problems occur in buildings. Here are some examples of water or leak history problems that can create a hidden mold problem in a building:

A one-time basement flood due to a burst pipe, sewer backup, or area flooding - the basement may now look clean and dry but significant mold contamination may be present in basement walls, under carpeted floors, or in building insulation
An older home with poor under-roof ventilation may have experienced condensation and moisture-related mold contamination of the attic insulation, roof sheathing, or hidden side of ceiling drywall; in northern climates such a home may have had ice dam leaks into wall cavities, producing hidden mold in building walls.
A home where plumbing leaks from an overflowing bath tub, leaky fixture traps, or supply piping leaks may have had leaks into wall and ceiling or floor cavities, leading to hidden mold contamination
A home with a history of recurrent a damp or wet crawl space is at extra risk of moldy crawl space insulation, producing mold species whose spores move upwards into the occupied space by riding normal air leaks and air convection currents.

A home inspector is expected to recognize these leak and moisture problems even though s/he is not performing an environmental inspection.

Also see MOLD TESTING by HOME INSPECTORS? for an opinion-text on the marketing of mold tests as a revenue source for home inspectors.

A Home Inspection is not an Environmental Survey of a Building

Unless the inspector happens also to be trained in mycology, forensic microscopy, and aerobiology, s/he will be focused on the condition of the building, not just on the presence of mold, but such a person is the best expert to identify leaks and moisture problems among other building risks.

Don't try to force the inspector to give an environmental report - it's outside the scope of a home inspection.

But do ask the inspector to be extra thorough and detailed about leaks, moisture, ventilation defects. And of course any conscientious and respectable inspector will also tell you if s/he happens to also actually see mold (or other out-of-scope hazards) during the inspection.

Key Mold Inspection & Testing References for Home Buyers

ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD describes what to do if problem mold is found in a building
HIDDEN MOLD describes methods used to find hidden mold in buildings
MOLD DETECTION & INSPECTION GUIDE describes how to look for mold in buildings
MOLD EXPERT, WHEN TO HIRE contains advice on when to hire a mold consultant to inspect and test a building. We identify factors such as the presence of people at extra medical risk (asthmatics, immune-impaired, infants) and leak history that increase the risk of a significant mold problem or that otherwise justify the expense of a thorough building survey for mold contamination.
MOLD CLEARANCE INSPECTIONS describes post remediation mold clearance inspection and test procedures, which could form a reasonable mold-screening inspection and test for a building
MOLD TEST KITS describes simple low-cost methods to screen building surfaces or building dust samples for problem mold
MOLD REPORTS describe what should be found in a usable and competent mold test and inspection report
WHAT MOLD LOOKS LIKE provides a photo library that helps anyone recognize mold on building surfaces and includes links to articles describing materials that are not mold but may indicate moisture problems that increase mold risk, as well as links to articles describing other non-moldy stuff often mistaken for mold

Frequently Asked Questions (FAQs)

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

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.

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.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
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

Mold Contamination Testing, Cleanup, Prevention: references & products

The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
Aerobiology, Building Science, Microscopy, & Laboratory References, an extensive technical bibliography
Allergens: what they look like in buildings
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) - The Atlas of Clinical Fungi is also available on CD ROM
Atlas of Mold Related Illness: Index of Symptoms and health, physical, neurological, psychological, and other complaint which people suspect may be mold or building-related.
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?
Clinical Mold References - Detailed bibliography of mold reference texts
"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
"Management of Powdery Mildew, Leveillula taurica, in Greenhouse Peppers," Ministry of Agriculture and Lands, British Columbia - Original source: www.agf.gov.bc.ca/cropprot/peppermildew.htm
Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
Fiberglass: Mold in Fiberglass Insulation© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation - DJF
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.
Fungi, Identifying Filamentous, A Clinical Laboratory Handbook, Guy St-Germain, Richard Summerbell, Star Publishing, 1996, ISBN 0-89863-177-7 (English) (buy at Amazon)
Looking for Mold Procedure: what mold is often found where in buildings - simple technical presentation
Meruliporia: the house eating fungus or "poria"
Mold Action Guide: Step-by-Step Instructions, What to do about mold, mildew, and other indoor allergens
MOLD APPEARANCE - WHAT MOLD LOOKS LIKE Photos of what mold looks like in buildings
MOLD APPEARANCE - STUFF THAT IS NOT MOLD Photos of NOT-mold material that is sometimes mistaken for mold
MOLD ATLAS & PARTICLES INDEX, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
MOLD BY MICROSCOPE Mold under the microscope - photo identification of the most common indoor molds found in buildings
Mold FAQs Answers to Most Questions about Indoor Mold, Mold Related Illness, Mold Cleanup, Mold Prevention
US EPA: Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens
Mold Test Kits - How to Collect and Send Your Own Mold Sample to our mold testing lab or to any mold lab you wish
Most Common Indoor Molds Found in Buildings, A Table of
Mycology, Fundamentals of Diagnostic, Fran Fisher, Norma B. Cook, W.B. Saunders Co. 1998, ISBN 0-7216-5006-6 (buy this book at Amazon)
Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
Rot concerns in buildings-some building mold such as Meruliporia incrassata "Poria" risks serious rot and hidden structural damage
US EPA: Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol

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.

Fiberglass building insulation and HVAC duct work insulation hazards
Sewage and Septic backup contamination in buildings: inspection, testing, remediation, & references to expert sources
Other environmental risks: Asbestos, carbon monoxide, electromagnetic fields, environmental illness, fiberglass, MCS - multiple chemical sensitivity, toxic gases, etc
Indoor Gas Sampling Plan for Residential Buildings lists a number of toxic indoor gases which we test for, depending on the building complaint and building conditions
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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