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Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY
MOLD: A COMPLETE GUIDE to TEST CLEAN PREVENT
ACTIVITY of MOLD in BUILDINGS
AGE of MOLD - Old is the Mold?
AIR CLEANER PURIFIER TYPES
AIR FILTERS for HVAC SYSTEMS
AIR TEST SAMPLING CASSETTE STUDY
AIRBORNE MOLD COUNT NUMBER GUIDE
AIRBORNE PARTICLE ANALYSIS METHODS
ALLERGEN TESTS for BUILDINGS
BROWN HAIRY BATHROOM MOLD
BIBLIOGAPHY for ENVIRONMENTAL HEALTH, MOLD, IAQ
BLACK MOLD, HARMLESS COSMETIC
BLACK MOLD, TOXIC & ALLERGENIC
BLEACHING MOLD, Advice about
BOOK MOLD, Moldy Book Cleaning
BOOKSTORE - ENVIRONMENTAL
CACTUS FUNGI / MOLD
CAR MOLD CONTAMINATION
CARPET DUST IDENTIFICATION
CARPET PADDING ASBESTOS, MOLD, ODORS
CARPET FUNGICIDAL SPRAY
CARPET STAIN DIAGNOSIS
CARPET & other STAIN TESTS
CARPET TEST PROCEDURE
CARPETING & INDOOR AIR QUALITY
CHAIN OF CUSTODY - TEST SAMPLE
CLEARANCE INSPECTIONS - MOLD CLEANUP
DIRECTORY of MOLD / ENVIRONMENTAL EXPERTS
DIRT FLOOR MOLD CONTAMINATION
Disinfecting Buildings with Bleach
DO-IT-YOURSELF MOLD CLEANUP WARNINGS
DUST ANALYSIS for FIBERGLASS
DUST, HVAC CONTAMINATION STUDY
EFFLORESCENCE, Salts & White / Brown Deposits
FEAR of MOLD - MYCOPHOBIA
Fiberboard Insulation Sheathing Mold
FIBERGLASS INSULATION MOLD
FIND MOLD, ESSENTIAL STEPS
FIND MOLD in BUILDINGS, HOW TO
FIRE DAMAGE vs MOLD DAMAGE
FLOODS IN BUILDINGS-mold
FOXING STAINS on books & papers
FUNGICIDAL SPRAY & SEALANT USE GUIDE
GAS DETECTION INSTRUMENTS
GAS EXPOSURE EFFECTS, TOXIC
GAS EXPOSURE LIMITS & STANDARDS
GAS TEST PROCEDURES
HOUSE DUST ANALYSIS
HUMIDITY CONTROL & TARGETS INDOORS
LAB PROCEDURES MICROSCOPE TECHNIQUES
LIGHT, GUIDE to FORENSIC USE
MEDIA BLASTING for MOLD REMOVAL
METHANE GAS SOURCES
MICROSCOPE DIGITAL PHOTOGRAPHY
MEDIA BLASTING for MOLD REMOVAL
METHANE GAS SOURCES
MICROSCOPE DIGITAL PHOTOGRAPHY
MILDEW ERRORS - MOLD PHOTOS
MILDEW REMOVAL & PREVENTION
MOISTURE CONTROL in BUILDINGS
MOLD: A COMPLETE GUIDE TO MOLD
MOLD EXPERT, WHEN TO HIRE
MVOCs & MOLDY MUSTY ODORS
MYCOPHOBIA, STAINS MISTAKEN for MOLD
MYCOTOXIN EFFECTS of MOLD EXPOSURE
ODORS GASES SMELLS, DIAGNOSIS & CURE
RENTERS GUIDE TO MOLD & IAQ
ROBIGUS & Wheat Rust Fungus
SMELL PATCH TEST to Track Down Odors
STAINS on & in BUILDINGS, CAUSES & CURES
THERMAL IMAGING MOLD SCANS
TRAPPED MOLD BETWEEN WOOD SURFACES
UV LIGHT BLACK LIGHT USES
VAPOR BARRIERS & CONDENSATION
VENTILATION in BUILDINGS
Volatile Organic Compounds VOCs
WATER ENTRY in buildings
Guide to testing mold on building drywall: This article describes proper procedures for sampling mold on drywall in buildings. Because moldy drywall or "sheetrock" is often the consequence of a building flood or wet floor, the moisture gradient in drywall varies at different heights above the floor surface. Because different mold genera/species vary in their hydrophilic nature (some molds love water more than others), different mold genera/species are likely to be found at different heights on a building wall. Which molds are most important to sample?
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.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
How to Test or Sample Building Drywall, Gypsum Board, "Sheetrock" and other Building Surfaces for Mold Using Clear Adhesive Tape
As I've explained in various articles and at our instructions for collecting and mailing a tape sample to our lab, different mold genera/species will be found growing on the same or nearby sections of drywall on a building surface, depending on several variables.
If the largest contiguous mold area in a building is trivial in amount, say 1 sq .ft., we would not test it unless we thought that the mold we see is representative of a larger mold problem I cannot see. Small areas of mold should simply be removed.
For larger areas of mold (certainly if more than 30 sq .ft. of area is moldy or if mold is growing on many surfaces in a building), you are looking for the dominant species present and particularly allergenic or toxic species present in the environment.
The photo at page top shows several colors of mold on a drywall surface. Still more mold may be present but still lighter in color and harder to see. Each of these may be a different mold genera or species. Which molds that we see on a building surface should be sampled? We explain the answers here. At Wall test cuts to spot hidden mold we discuss finding mold on the wall cavity side of drywall. Also see MOLD RESISTANT DRYWALL for a discussion of that product type as well as a list of drywall or gypsum board industry standards and drywall product MSDS sheets.
This article is part of our 'how to' photo and text primer on finding and testing for mold in buildings using simple clear adhesive tape on suspect or visibly moldy surfaces. Also see MOLD GROWTH ON SURFACES, PHOTOS and MOLD APPEARANCE - WHAT MOLD LOOKS LIKE.
How to Decide Where to Sample for Mold and How Many Mold Samples To Collect
Collect one mold tape sample per location; do not use the same tape to sample from multiple locations.
This condition often occurs, but the different genera may be as close as inter-mixed and even overlapping in the same area, to growing several feet apart on the same wall, to growing in the same building but on different materials on different surfaces.
In this case, tape sample #1, the bottom mold, was Stachybotrys chartarum, tape sample #2, the middle mold, was Cladosporium sphaerospermum, and the top tape sample, #3, was Aspergillus flavus. Of these three, the Aspergillus is the easily-airborne toxic spore which is more likely to be a problem in the building if it is present in sufficient quantity.
How to Prepare & Save Mold Tape Samples for Mailing to a Mold Test Laboratory
In this photo detail you'll see that using a new and clean zip-lok™ bag, we placed several surface tape samples on the same bag. If you can't assure that the bag surface is clean between tape sampling, use a new bag for each sample.
Are you collecting too many mold test samples?
There are nearly always multiple mold species present in any environment where mold producing conditions are present.
We sample surfaces likely to host different molds, focusing on surfaces which appear to represent mold or mold-suspect material growing over large areas in the building. Don't collect and send 50 samples. If you find you want to collect a great many samples it would probably be smarter and more economical to bring in an expert to survey the building and who can sample more strategically.
Interrupted Mold Growth Pattern on Building Drywall - Why Does Mold Growth Sometimes Stop in Straight Lines?
In our photographs shown above the thick black mold growth on drywall in a wet basement appears to nearly "stop" in a neat horizontal line just about four feet from the floor surface. Why?
Stachybotrys chartarum, which dominated the mold on this drywall, really likes wet conditions. As we explained above, the genera/species of mold growth may vary on a surface of the same material as a function of variation in moisture levels in the material.
In our photo at above right we show by having made a test cut into the moldy drywall that mold growth stopped its rapid advance up the drywall when it encountered the horizontal tape joint between the lower and upper runs of drywall in the building. We have found two common explanations for this observation:
Frequently Asked Questions (FAQs) about mold growth on drywall in buildings
Question: What are the necessary conditions for mold growth on building drywall and in the wall cavity?
I had energy efficient windows installed in my townhouse over a year ago. This past spring one of the master bedroom windows leaked after a rain storm because the caulking failed. The company immediately came out and recaulked the window and it hasn't leaked since.
Mold growth in wall cavity below a leaky window
[Photo at left provided by InspectAPedia, taken from a New Jersey home and not the building discussed by this reader, shows mold growth on drywall and on wallpaper beneath a leaky window. A single rainstorm combined with the window having been left partly opened caused this mold growth.
After checking the basement ceiling cavity below this window as well as in the wall cavity itself, our investigation found that the total moldy area was less than 30 sq.ft. and the mold cleanup could be handled as a normal renovation job. More examples of mold growth on and in wall cavities and hidden by wallpaper are shown at MOLD GROWTH ON SURFACES, PHOTOS - Ed.]
My concern is that I now have a water stain under the window on the drywall, and since I have a mold allergy, I'm wondering if there might be mold on the inside of the drywall. I read your article on testing the dry wall but as mentioned in the article would rather not cut into it unless it's necessary. I looked at other articles but didn't see one with a picture resembling the water stain I'm concerned about. What would you recommend?
By the way, this is a very helpful website. I was considering using ozone for any possible mold in my place but see from your article that's not a good idea.
Continued: I emailed you recently about the possibility of mold forming on the inside of drywall under a window that leaked last spring when it rained.
I contacted a bonded company about replacing the drywall. The gentleman I spoke on the phone with told me that he's attended mold seminars and that mold requires an ongoing source of water or moisture over an extended period of time to grow. In his opinion, since my leak occurred only once during a rain storm that lasted an hour or so, there's little or no chance mold could grow on the inside of the drywall under the window. He also said that since the water stain is barely visible, this is more reason to conclude there's no mold on the inside of the dry wall.
I thought it would be a good idea to check this on your website, but didn't find any topic that seemed related to the conditions for mold formation, so I thought I should email you. Is what he says about mold formation accurate? And if so, is it reasonable to conclude that there's probably no mold on the inside of the dry wall under the window that leaked?
I'm hoping he's right, because I won't have to replace the drywall. I'll replace it if necessary, though.
Thanks again for your help. G.N.
Reply: Even a single event water leak is likely to lead to mold growth in building ceiling or wall cavities - it depends on ...
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with mold, hidden mold, and with tracking down just how much water leaked into the building and where it went.
First, how disappointing that your new windows leaked - certainly a wet wall below a leaky window is not particularly energy efficient, and indeed it could become a mold reservoir.
The risk of a mold problem that you can't see but that is significant enough to merit removal is not something I nor anyone should guess at by email nor by telephone (that is, with no building inspection) with so little information. MOLD EXPERT, WHEN TO HIRE provides advice on deciding (or not) to hire someone to inspect and test for mold contamination.
Watch out: mold testing alone, without a building inspection, case history, and occupant interview, is not reliable.
I would not rely on "mold tests" - a test, especially an air test for airborne mold, performed without an expert diagnostic inspection of the building is just not reliable in cases where the result is "negative".
Continued reply: G., your bonded company expert is mistaken, as you can see in our example photo above showing mold growth in the wall cavity and behind wallpaper below a window following a single event leak.
A single water entry event can cause mold growth in a building cavity, on the wall cavity side of drywall, in the wall insulation, on the kraft paper insulation facing, on the building structural wall wood studs or cavity side of the exterior wall sheathing.
Your expert would, however, be correct, if s/he asserted that the extent or size or severity of mold growth from a single event leak depends on the size of the leak, the amount of water entering the cavity, where it went, what materials got wet, and the moisture exit rate from the building cavity.
Unlike your expert, beyond that advice I'm reluctant to promise what is or is not in a building cavity on a building I've not studied. Often an expert on site finds evidence of chronic leaks that a normal building owner may never have noticed. Very often very small leaks or wet spots do not produce a significant problem mold reservoir.
Why even a single building leak can cause significant mold growth in 24-48 hours
But because building wall or ceiling cavities dry out very slowly, leaks into a wall or ceiling, even from a single event, can initiate problem mold growth in those areas. In general, if a building interior or building cavity interior contains mold friendly organic materials such as wood, paper, drywall, fabrics, drywall, mold growth can be expected to occur if the area remains wet for 24-48 hours. Low temperatures can sometimes slow down mold growth so a building that was wet during freezing weather may have a bit more time.
What happens to mold in a building wall or ceiling cavity once the area has dried out?
When the building cavity finally has dried, several conditions are likely to occur:
How do we decide if destructive or invasive inspection of building cavities is justified
In general, if there has been anything but the most absolutely trivial leakage into a building wall or ceiling cavity, and if thus we decide to investigate, I recommend choosing the one or two most suspect leak areas, where there is the most evidence or suspicion of the area that received the most water or was the most wet. In those areas I'll make a small test cut, perhaps 2" x 4" into the ceiling or wall, through the drywall. There we perform a visual inspection for visible mold on all surfaces and materials; if there is insulation present we also collect a vacuum sample of that material, and we collect tape samples of any visible mold on any of the newly exposed surfaces.
If that most-suspect area is "clean" of any strong suggestion of mold contamination, we don't cut or dig further without some other compelling reason to do so.
What is appropriate when there has been building leakage and where there is a concern for possibly significant hidden mold contamination is to make a decision about whether hiring an expert is justified in a particular case - see MOLD EXPERT, WHEN TO HIRE for advice on making that decision.
Question: why is this black mold growing on these drywall ceilings & walls?
Reply: Summary of common reasons for mold growth on drywall
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem. That said, here are some things to consider:
Possible reasons for indoor mold growth ?
In all cases of indoor mold growth the mold needs food (wood, paper, organic material), oxygen, and water; some molds thrive on light, some are tolerant or intolerant of UV, and other factors.
Moisture, water, leaks, condensationa are key determinants in indoor mold growth
Of all of these, water is the key necessary ingredient which we can track and which is inviolate - that is, no water, no moisture = no problem mold growth.
But I note that your middle photo looks as if it is a ceiling and because there is a vent therein I suspect this may be over a bathroom; Common moisture sources for such an area might include
The density of mold growth in your photos suggests that there have been leaks from above. But in some cases even without actual water leaks into a ceiling or wall we can see dense mold growth on building drywall caused by other wet building conditions (flooding of the floor for example, or a heating or steam pipe leak).
The fact that the mold seems to track or be more dense along lines resembling either drywall joints or actual locations of framing would argue for either leaks from above penetrating at drywall butt joint seams or quite often, temperature differences (wood framing in contact with drywall produces cooler temperature than insulated ceiling cavities).
Temperature variations can in turn invite higher levels of condensation on cooler surfaces in those areas. We also see this effect in THERMAL TRACKING & THERMAL BRIDGING
So even when we don't see leak stains showing a water source, the mold growth pattern might track moisture gradient in the materials and thus suggest something about its cause.
You will need to remove the moldy drywall in any case, as well as any insulation that has been wet or exposed to mold.
That will let you inspect the wall or ceiling cavity for leaks as well as to check that the bath vent fan is actually venting and is properly used.
`Actually I know very little knowledge about mould. My landlord said the mould was caused by the lack of heat. Can you show me some ideas?
Does the water stain of the second picture show water leakage? This house is more than 40 years old.
There is no indoor ventitaltion system, the fan in the bathroom has been blocked for long time and the fan had not been insulated well.
There's no fan to transfer gas to outside in the kitchen. - Y. 6/5/2013
Mold is is not directly caused by lack of heat - cooler temperatures in fact retard mold growth, if all other conditions are equal. But lack of heat that leads to condensation problems or to a frozen burst pipe and leak can indeed cause or encourage indoor mold growth.
And I would agree that heating a building, as it dries a building, would avoid problem mold growth provided that there are not leaks or abnormal moisture sources.
If there is mold there is a condensation or leak problem to find and fix. If the mold is on the wall cavity side of the plastic then there are leaks into the wall cavity - either water leaks or air leaks, perhaps combined with incomplete or improper insulation. I'd have to see more detail to have a more confident opinion. From your photo I'm not even sure what's ceiling and what's wall.
Some speculative examples of what could be going on include:
The suggestions I made earlier about tracking down leak and moisture sources should, perhaps in this case, be combined with inspection for air leaks into the cavity from indoors or from outside.
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