Guide to Hidden Mold in Rental Homes, Apartments, Offices
- HIDDEN MOLD RISKS for RENTERS - The mold you see or the mold you tested may not be the only concern nor the main risk. How to handle hidden or "non-visible" mold contaimnation complaints or problems in rental property, apartments, rental homes, offices, Hidden mold contamination testing advice for rental tenants or Hidden mold contamination complaint advice for landlords
- POST a QUESTION or READ FAQs about hidden mold problems in rental apartments
This article describes the steps that a tenant in a rental apartment or rental home can take to look for and test for
hidden mold contamination, we discuss when such testing is appropriate, and we make suggestions on how to inform building management of a mold problem, what to expect the rental property managers to do if they
are going to address a mold problem properly, and what the rental apartment tenant needs to watch out for during
a mold investigation and mold remediation of their home.
An easy-to-print PDF version of this article is here.
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A Guide to Possible Hidden Mold in Rental Apartments, Houses, Offices
The mold that you *see* may not by any means be the whole problem, or even much of the problem; various species could be
in building cavities and in the HVAC system.
Too often we find that "black mold" on building surfaces has received attention but hard-to-see Penicillium sp. or Aspergillus sp. (for example) remain in large reservoirs on building surfaces or in insulation.
Magic bullets: Also, "bleaching mold" or "fogging" or "encapsulating" mold is never a successful remedy for a moldy building.
The places where mold is growing must be found, moldy material removed, exposed surfaces cleaned, and the causes of mold
If the area of mold growth is large (more than 30 sq ft) the work needs to proceed with special
procedures to avoid spreading moldy dusty debris around.
Tenant-identified possible mold reservoirs
The tenant or building maintenance staff may have already identified apparent mold reservoirs or sources, and of course there could be other sources from other leaks or problems they haven't
Roof leaks - can have leaked into ceilings and walls; depending on what building materials used, they could be moldy with
HVAC systems - If there is a common A/C duct system which has become mold contaminated, no amount of cleaning in your immediate
apartment would be sufficient since it is possible that the whole system needs to be cleaned, or possibly some duct
sections replaced, and the cause corrected. Also it is common for A/C condensate or water from a chiller system to
leak; water could have leaked into your closet ceiling and walls, also creating a problem mold reservoir.
Building insulation - often building insulation has become mold contaminated but looks "clean" to the naked eye. Few mold inspectors test this material, yet it is often discovered to be the principal problem mold reservoir in some building areas.
Very often when I visit a site I find other leaks and mold sources that need to be addressed, so I wouldn't assume these
are the full extent of what needs attention.
Continue reading at MOLD ACTION ADVICE for RENTERS or select a topic from the More Reading links shown below.
Or see MOLD / ENVIRONMENTAL EXPERT, HIRE ? - figure out when to hire someone
Suggested citation for this web page
HIDDEN MOLD RISKS for RENTERS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.
Green link shows where you are in this article series.
- RENTERS & TENANTS: MOLD ADVICE
- MOLD: A COMPLETE GUIDE - home
- ACCEPTABLE MOLD LEVEL
- ACCURACY OF VARIOUS MOLD TEST METHODS
- ACTION GUIDE - WHAT TO DO ABOUT INDOOR MOLD
- AIR TEST FOR MOLD: ACCURACY
- CARPET MOLD CONTAMINATION
- CRAWLSPACE MOLD ADVICE
- DISASTERS: BUILDING INSPECTION & REPAIR - home
- DRYWALL MOLD TESTING
- DUST SAMPLING PROCEDURE
- EMERGENCY RESPONSE, IAQ, GAS, MOLD
- HIDDEN MOLD, HOW TO FIND
- INDOOR AIR QUALITY IMPROVEMENT GUIDE - home
- INSULATION MOLD CONTAMINATION TEST
- MILDEW in BUILDINGS ?
- MOLD ACTION GUIDE - WHAT TO DO ABOUT MOLD
- MOLD AGE, HOW OLD is the MOLD?
- MOLD APPEARANCE - WHAT MOLD LOOKS LIKE
- MOLD APPEARANCE on VARIOUS SURFACES
- MOLD APPEARANCE - STUFF THAT IS NOT MOLD
- MOLD CLEANERS - WHAT TO USE
- MOLD CLEANUP, DO IT YOURSELF
- MOLD CLEANUP GUIDE to GET RID OF MOLD
- MOLD CLEARANCE INSPECTIONS
- MOLD / ENVIRONMENTAL EXPERT, HIRE ?
- MOLD EXPOSURE STANDARDS
- MOLD PRODUCTS, INEFFECTIVE
- MOLD RELATED ILLNESS SYMPTOMS
- MOLD SPRAYS, SEALANTS, PAINTS
- MOLD TEST vs. PROBLEM DIAGNOSIS
- MOLD TEST KITS
- MOLD TEST METHOD ACCURACY
- MOLD TEST REASONS
- MOLD TESTING METHOD VALIDITY
- MOLD TESTING SERVICES
- MVOCs & MOLDY MUSTY ODORS
- MYCOTOXIN EFFECTS of MOLD EXPOSURE
- OZONE for MOLD OR ODORS
- FAQs below discusses field reports of problems & solutions for this topic
Frequently Asked Questions (FAQs)
Click to Show or Hide FAQs
Is it safe to have plastic flooring over a wood floor over a concrete slab foundation, regardless of anything else, or is the plastic flooring a moisture trap that would probably cause a mold buildup even without a flooded foundation for two months? Has anyone looked at this? At all?
I looked at the Building Code of Canada, hoping it would helpfully say "Don't ever do this!!!!!" and it doesn't, alas.
My landlord put the plastic layer down about 6-7 years ago. In the bathroom (currently gutted) there was wood over concrete, and ceramic and vinyl over the wood, and the wood had rotted in multiple locations. In the kitchen there is linoleum/vinyl over wood over concrete. The floor under the sink is rotted and the boards elsewhere are warped, but the city hasn't ordered the landlord to fix it. I have no idea what's going on under the plastic in the main area because I don't know how to have a look without causing damage. I'm looking for ammunition to get the floors in the main room/kitchen officially looked at.
I can't afford to pay a consultant (on disability in Montreal) but was hoping that you could point me to something that might help. I didn't see anything on Inspectapedia but maybe don't know what to look for. If you want more details I can send you them.
Thank you for all the information you do have on mold. It's been very helpful. - A.C., Montreal, 11/21/2013
I agree that this topic has not been pinned down, as I will explain in a moment. A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer than we can give by email alone. You will find additional depth and detail in articles at our website.
That said I offer these comments:
I have observed that trapped moisture within a floor structure indeed will ultimately rot the materials. All mold is everywhere all the time - it's the concentration that varies.
So all we need is a few mold spores of wood rotting fungus to have been present when a floor, perhaps dry at the time, was enclosed and sealed such that later water entry from below initiates mold growth and rot.
But still, I have inspected a number of floor structures built on concrete that were sealed from above and later disassembled to show no rot damage.
The key variable, as you pose, is leaks and water entry. In short, if the building does not leak from above or up from below through the foundation or slab, the enclosed floor cavity, say sleepers on concrete, topped with perhaps subflooring, finish flooring, and tile or laminate or vinyl sheet flooring, survives quite well.
If the same floor structure cavity is wet from any source and is not opened and dried promptly mold growth and later rot can be expected to develop.
I believe that the codes are silent on this point because of the variables involved and the anticipation that good building design and proper maintenance is not supposed to tolerate water entry up through the floor of an occupied space. In other words, build and maintain your building to keep water out.
That approach is probably more cost-effective and easier to specify than to try to make every single indoor component able to withstand flooding.
To be clear, we could just as well say don't ever enclose a wall or ceiling, because water can get in and cause trouble.
But we do enclose them. (And water does leak in and cause trouble.)
Moving on to the specific case you describe,
re: "The floor under the sink is rotted and the boards elsewhere are warped, but the city hasn't ordered the landlord to fix it."
suggests to me that
- there are building leaks that need to be corrected, and that are causing costly damage to the building
- If typical building materials used such as drywall & fiberglass insulation are being wet, there is a reasonable risk of problematic mold contamination indoors too.
Please take a look at the article series I've written specifically for people in your situation, beginning at RENTERS & TENANTS: MOLD ADVICE and let me know if questions remain after you've seen that material.
Ask a Question or Search InspectApedia
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Technical Reviewers & References
Publisher's Google+ Page by Daniel Friedman
Click to Show or Hide Citations & References
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
- 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
Allergies, Allergens, Allergy Testing in Buildings - References & Products
- Air Conditioning System Blower Fans & Filters Cascading for Optimum Indoor Air Quality
- 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.
- Atlas of Mold Related Illness Symptoms & Complaints - long list of both documented, studied mold related illness, and complaints ascribed to mold contamination or allergens in buildings
- Cat Dander: how to inspect and test a building for past or current presence of cats, cat hair, cat dander, and cat allergens
- Clinical Atlas of Mold Toxicity - An Online Description of Toxic, Pathogenic, Allergenic Fungi, Fungal Diseases
- Fiberglass Insulation Contains Mold© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation
- Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
- Mold Action Guide detailed guide on finding, removing, and preventing indoor mold contamination
- Odors, Odor Detection, Smells, & Gases how to find and identify sources of noxious or toxic odors and gases
- Other environmental risks, Our much longer list: Asbestos, carbon monoxide, electromagnetic fields, etc.
- Ozone: The Use of Ozone Indoors for Control of Odors and Mold
Removal in Buildings: A Summary of Hazards and False Claims.
- Pollen Allergens: identification, plant pollen and indoor air quality
- Products to Reduce Mold & Allergy Problems to reduce indoor mold or allergen levels: air cleaners, air purifiers, dust mite covers, vacuum cleaners, crawl space vents
- 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
- Sewage and Septic backup contamination in Buildings: inspection, testing, remediation, & references to expert sources
- Action Guide: What to do about mold, mildew, and other indoor allergens
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,"
Department of Plant Microbiology and Pathology,
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)
- MOLD in BUILDINGS 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