Based on this inspector's experience with inner wall sampling during mold investigations from 2003 to 2011, there is virtually always an active or recent source of moisture in a wall when unusual mold conditions are found in a wall. Very often finding that moisture source will involve looking for defective caulking on the exterior side of a wall, or will have to be found by interviewing the client about past moisture issues in that wall, but there always seems to be a moisture source associated with mold problems in a wall.

In other words, such problems do not appear to result from something that happened during construction, but inner wall mold appears to be related to something that happened closer to the time of the inspection. This cause can be found by conducting a detailed inspection of the surrounding area.

Low spore levels are found when leaks are not present in a wall. If construction time rain caused mold, then in Florida where it rains a lot, I would find mold in walls where no moisture defects are found, and would conclude that that mold resulted from rain during construction, but this does not happen.

As stated above, a detailed inspection of a wall with elevated spore levels will reveal some defect in or near that wall that caused moisture intrusion into the wall.  I can remember very few exceptions: a large bank in the Florida Panhandle became moldy during construction; however, construction lasted for a few years, and three hurricanes occurred during construction. In addition, delays had resulted when the builder could not locate weatherproofing capstone structures for the roof.

Another time in St Lucie County we conducted an inspection for a builder, mold was found, and this problem also occurred not because of normal construction period rain, but because of hurricanes that occurred during construction.

And one other property had mold in the attic on trusses because of hurricane period rain.

In all other properties when mold has been found in a home's or building's walls, it has been associated with water intrusion or severe condensation that did not appear in any way to be related to construction time rain.

Based on this inspector's years of mold inspection experience, inner wall sampling is very reliable, and much more effective than air sampling alone, which often results in false negatives. If inner wall sampling did not work, then I would not do it. It takes much more time and effort to sample air from within a wall than it does to set up a pump in the center of a room and take a room air sample.  Inspectors do it with no ulterior motive; inspectors conduct inner wall sampling because it provides valuable information that cannot be obtained from room air sampling.

If water damage to a wall is obvious, and in the inspector's experience mold is very likely in that wall then the inspector may skip sampling in that wall and make a reasonable assumption that mold exists in that wall.

If you suspect a mold problem do not rely on a mold inspector to conduct room air testing for mold alone. Often to get to the root of a problem, inner wall sampling can be very effective and reliable.

In my personal air testing experience I much more believe the results of inner wall sampling than the results of room air sampling. Room air samples often give false negatives (show no spore problems even when mold is a problem). This is because in a room mold spores are very often trapped behind a wall, but in a wall mold is not as likely to be trapped and separated from the sample cassette. Sometimes room air samples give false positives (show elevated spore levels even when mold is not a problem). Inner wall samples are usually true and reliable because air in a wall is not exposed to wet bathroom carpets, dusty window sills with condensation problems, moldy fruit in the garbage, and dusty carpets, such conditions can give false positives in a room but such conditions do not exist in a wall to give false positives.


Mold inspector mold testing indoor air West Palm Beach Lauderdale to Miami.