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The fact that mold is "hidden" in buildings does not mean one cannot find it. We look by context: where do we see leak stains, or where do we see building practices most likely to have produced a hidden leak or moisture problem? Ice dam leaks in walls, hidden plumbing leaks, roof spillage by the foundation, are all common clues that often track to a wet building wall or ceiling cavity and from there to a hidden mold problem which may need to be addressed.

This document 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. This procedure 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. Also see MOLD GROWTH on SURFACES for an index of what mold genera/species are frequently found on various building surfaces and materials.

© Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Hidden Mold Behind Paneling in Bathrooms and Basements

While we do not recommend wholesale demolition of rooms where there is no visible external mold, if an area has been wet by leaks or flooding, and where paneling covers walls (or ceilings) it is common to find problematic mold growth behind paneling even if it looks quite clean on the exposed or room side.

Some careful removal of sample panels in the most-suspect areas (most exposed to moisture or leaks) can disclose a hidden mold problem in a building.

If initial exploration for hidden mold shows what may be a large area of mold, say 30 sq .ft. or more of moldy surface, work should stop for professional evaluation and to avoid spreading moldy dust throughout the building.

All mold investigation work, demolition, and cleaning should be performed using the appropriate protective equipment.

Remove bathroom paneling to expose hidden mold: The photo above shows an extensive mold colony found growing on the face of drywall which had been covered by wainscot paneling in a bathroom. More mold growth was on the hidden side of the paneling itself. None of this mold was visible on the exposed bath surfaces before I pulled off this panel. Why did I pull it down? There was evidence of a history of prior leaks in building walls and wet floors in this area. Superficial cleaning and a "cover up" installing new paneling was all that the building manager thought was required. Unfortunately it led to a greater cost later to properly demolish and clean this area.

Remove basement paneling to expose hidden mold: In this photo of me pulling open the edge of basement paneling more than 20 years ago, we found that a large mold colony had been generated on the drywall surface hidden behind the wood paneling. Forty years previously, and 20 years before this inspection photo was taken, a single event basement flood had occurred. The owners had pumped out water and dried the basement within a few hours of the event. There was almost no discernable clue on the exposed side of the paneling itself. Yet because the wall cavities themselves were not opened at the time of the flood, hidden surfaces and materials stayed wet long enough to initiate a large fungal colony. It appears that once the mold colony was established, periodic elevations in basement humidity were enough to keep the mold colony happily growing along. One of the home's occupants who grew up in this home developed severe asthma. She told me that if she simply stood at the top of the basement stairs above this room she would have an asthma attack.

Warning notice

Guidelines defining what's a "large amount" of mold and what's reasonable for a homeowner to handle have been published by several states including New York and California. Links to some key documents describing mold cleanup and mold remediation procedures are at InspectAPedia.com/sickhouse/action.htm#clean.

People who are allergic, asthmatic, infant, elderly, immune-impaired, etc., should not disturb mold and should not be in the area where mold remediation is being performed. Consult with your doctor, health department or other professional before tackling this job yourself.

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Daniel FriedmanInspectAPedia.com/sickhouse.htm

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MOLD INFORMATION CENTER
MOLD ACTION GUIDE - WHAT TO DO
MOLD DETECTION & INSPECTION
HOW TO LOOK FOR MOLD
WHAT MOLD LOOKS LIKE
ATTIC MOLD
BASEMENT MOLD
BASEMENT MOLD WATER IMPACT
CRAWLSPACE MOLD
DRYWALL MOLD
FIBERGLASS MOLD
MOLD on DIRT FLOORS
MOLD on or in CARPETS
ITCHY FABRICS
HIDDEN MOLD, HOW TO FIND
  Hidden Mold Behind Paneling
  Hidden Mold Between Framing & Sheathing
  Hidden Mold in Flooring & Subflooring
  Hidden Mold in Wall Cavities
  Light colored toxic molds
  Moisture Gradients and Mold
  Other Places to Look for Hidden Mold
  Recognizing Cosmetic Mold
  Spotting Hard-to-See Mold
  Use a Flashlight to Find Mold
  Wall test cuts to spot hidden mold
INSULATION MOLD
DO-IT-YOURSELF WARNINGS

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

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• Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
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More Information on Building Diagnostic Inspections and Repairs

Mold and Allergen Recognition and Identification - Not All "Black Mold" is Harmful; Some Suspect Stuff is Not Mold

• How to Find and Test For Mold in Buildings - Looking for Mold - A 'how to' photo and text primer on finding and testing for mold in buildings
• 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
• Frequently Asked Questions About Mold -- 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
• Contact Us to arrange mold/IAQ building on site inspection and testing.

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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

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.

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