The moldy wall

The insured entered an insurance claim based upon discovery of a dark brown moldy growth on an interior wall of the insured’s living room.  The insured was a physician and a toxicologist with specialized forensic training in microorganisms.   GEI was assigned to conduct a limited Indoor Air Quality (IAQ) assessment and to discuss mold related issues with the insured.

The two-story home was constructed on a raised foundation with an elevated landscaping planter adjoining the northwest exterior wall of the living room, in the front courtyard area.   The insured related that several locations in his home appear to have been impacted by mold, and one particular area in the living room had visible dark brown staining on the lower interior wall.   The home was about 80 years old.   It had “lath and plaster” wall construction with raised wood floors on joists.

Fungi were apparent in one small area on the living room wall. The insured moved furniture to allow for inspection of the area, and granted approval to drill one ¼-inch diameter hole for installation of a sampling device.

The insured stated that he had two additional downstairs locations that he identified as having possible damage due to excessive moisture: bathroom and office.

We found the ceiling of the downstairs bathroom to have several small sections of chipped peeling paint with no visible mycelium or discoloration that would be typical of most mold.   However, certain species of mold do have a color that may appear as off-white, and resemble the color of paint, so we took samples from the peeling paint.   We also inspected the office location.   It appeared to have been repaired on one or more occasions.   No moldy material was observed, however, we took samples.

The indoor air quality environmental site assessor is normally interested in two-primary criterion or principles in mold investigations: comparing the indoor with the outdoor air-mold levels (quantity); and comparing the indoor and outdoor air-mold genera (quality). Levels of mold contamination indoors should be equal to (and hopefully less than) outdoor air. The types of mold, or genera, found indoors should not differ greatly from that found outdoors. After remediation of a contaminated site if the indoor air (in quality and quantity) does not differ significantly from that of the outdoor air, the site is considered “clean” and is therefore usually considered to be remediated. The type of mold genera was classified at this site by the laboratory analyses, after the microbiologists cultured the swab and agar dish samples that were collected at the residence. This procedure was followed for closure air sampling after remediation of building components was completed.

Quantity—As you can see from the following table, the number and genera of indoor fungal organisms compared favorably with that found outdoors; indoor living room air produced about 16% less viable fungi than outdoor air on the front yard patio. The interior of the north wall of the living room had about 50% more viable fungi than outdoor air, which indicated a moderately high level of infestation of the wall interior, and needed to be remediated.

Quality—Mold found at this residence was similar in genus and number.   One exception: viable Alternaria genera were found in the indoor living room air, but at less than 10% of the sample.   The interior of the north wall had over four times the number of viable Aspergillus genera as found in the indoor MXA culture sample (133 colony forming units/cubic meter compared with 33 cfu/m3).   Every known fungal organism can be identified to the genera (first), then most to the species level (second).   The Aspergillus organism found in our limited investigation was not identified by the laboratory to the species level (only to the genera level); however, future IAQ assessments at a lower level of detail would report species because of possible medical implications.


Sample # Location      Total Spore Count/M3  Notes
1-Swab North living room wall surface   <10 None Detected   Slight dark brown staining visible
2-Tape North living room wall surface  No visible growth   Paint solids
3-Culture  Interior of north living room wall 233  Moderately high level for wall interior
Aspergillus (57%),
Penicillium (29%),
Cladosporium (14%)  Sample Vol=30L
4-Culture Center of living room    133   Aspergillus (25%),
Penicillium (42%),
Cladosporium (25%),
Alternaria (8%)   Sample Vol=90L
5-Culture  Outdoors in front yard on slate patio area
155  Aspergillus (36%),
Penicillium (57%),
Not Identifiable (7%)  Sample Vol=90L
6-Swab Ceiling of downstairs bathroom <10 None Detected  Off white color of paint; no visible mold
7-Tape Ceiling of downstairs bathroom No visible growth   Paint solids
8-Swab Office @ lower-west wall    <10 None Detected  Off white color of paint; no visible mold
9-Tape Office @ lower-west wall    No visible growth   Paint & plaster repair compound solids
The office and bathroom were essentially clean, but the living room wall was clearly infected.   Biological organisms detected within the wall exceeded the background or ambient indoor and outdoor air quality conditions and needed to be remediated.   So what was the cause?   The living room interior wall was located on a common wall with a raised-exterior landscaping planter.   This common wall was impacted internally with moderately high levels of fungal organisms. Aspergillus, penicillium and cladosporium genus were found within the living room wall at an overall level about 50% higher than outdoor levels.

The insured watered the exterior raised landscaping planter by  use of a sprinkler system.   There was a crawlspace vent located in the planter that the sprinkler had been spraying water into.  The mold growth within the wall was the result of the watering that led to saturation of the wall substrate through the wall-vent for the crawlspace.  That long-term sprinkler water source led to the mold condition.