Basement Mold: How to Find and Test for Mold in Basements InspectAPedia® -
How to inspect & test for mold in building basements
How to inspect & test for moldy basement insulation or basement contents & stored items
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This document gives advice on how to find and deal with mold in building basements and in basement insulation. This is a chapter of
"How to Look for Mold" 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.
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.
BASEMENT MOLD: finding the problem mold, allergens, or other particles in basements
Leak History: Examine the basement for its evidence of recurrent leaks and water entry.
Finished Basement Organic surfaces: Look carefully at organic surfaces such as wood, drywall, and carpets in a finished basement:
Walls: drywall, especially low on walls, in wet corners, behind furniture, and in areas of leaks from above
Ceilings: drywall, especially in areas of leaks from above, such as under baths or kitchens, and at the walls below roof eaves
in cold climates where ice dam leaks may have sent water into wall cavities; look at hot water heating baseboard locations
for bleeder vents or other leak points
Ceilings: suspended ceilings: look on both sides of ceiling tiles for visible mold or leak stains; don't ignore possible mold in fiberglass-based ceiling tiles.
Ceilings: inspect framing - the joists of floors above, and the exposed side of subflooring of the floor above. See our warning about mold growth on pine boards discussed at Attic inspections above.
Floor: wall to wall carpeting is a very common mold and allergen reservoir. Don't ignore possible reservoirs of high levels
of mite fecals and pet dander including pets from prior owners. Look for other signs of pet presence in the building such as
scratches on doors and trim.
Un-finished basement mold: Look carefully at organic surfaces in un-finished basements or behind or above finished surfaces
Look for evidence of prior basement water entry - mold is more likely to have grown on wetter surfaces first in a
basement. Stains on the floor or remnants of cardboard boxes that were there, wet, and then removed, are important clues.
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.
Inspect the back side of stairs, especially the lower treads and risers
Don't assume that because there is no visible mold on surfaces that there is not a problem mold reservoir in exposed insulation.
Basement contents be sure to inspect furniture and stored materials in a basement where mold is suspected, such
as cardboard boxes and their contents and the under-side of furniture and game tables. Often we find serious mold growth on
the un-finished surfaces of wood objects, probably because the absence of a coating means that such surfaces take up more
moisture than other sides of the same item.
Mold hidden in basement insulation or on basement contents
Even when there is no visible mold, don't ignore exposed fiberglass insulation as a possible mold reservoir.
A basement which was previously moldy or wet, or a basement which stored a collection of moldy boxes or cartons of moldy papers and files may have been
may have left behind a large mold reservoir in the basement fiberglass insulation and in settled dust.
In the first photo shown here the basement insulation looked clean to the naked eye, but a history of basement
flooding led us to test the insulation.
We found high levels of Aspergillus contamination in this
yellow fiberglass insulation which, to the naked eye, looked quite clean.
If there is visible mold on other basement surfaces, don't forget to also check the condition of basement insulation that
your insurance company, mold consultant, or mold remediator may want to leave in place because it "looks clean".
In the photograph shown
here, not only was there extensive Stachybotrys chartarum contamination visible as "black mold" on the
basement drywall, a special vacuum test of the fiberglass insulation in this basement ceiling disclosed high levels of Aspergillus versicolor, Aspergillus sp., & Penicillium sp..
These three photos of fiberglass insulation, drywall, and a wall cavity which was cut open
show the value of exploring building cavities where there may have been leaks from above, regardless
of whether we're exploring in above-grade level living space or below-grade level basements.
A roof leak had wet
these wall cavities, leading us to test the insulation for mold and to inspect further for moldy drywall. The photos
also illustrate that luckily not every building leak into every building cavity is going to cause visible mold
growth on the hidden surfaces of drywall.
See BASEMENT MOLD WATER IMPACT for a discussion of movement of moisture (and mold) from a wet basement or crawl space up through the occupied building space and into a wet moldy building attic.
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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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
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