Mold Growth On Drywall / Plasterboard

Some molds, such as Stachybotrys, Chaetomium, and Aspergillus versicolor can grow readily on wet drywall and produce significant quantities of harmful toxins (mycotoxins).

A Finnish study reported that wet drywall supported heavy growth and significant mycotoxin production of 4 common indoor molds- Stachybotrys chartarum, Aspergillus versicolor, Penicillium spinulosum, and Streptomyces californicus (Murtoniemi, Hirvonen et al. 2003) .

Drywall often becomes contaminated with mold spores during manufacturing and installation. A study of 13 drywall panels purchased in 4 Copenhagen, Denmark shops reported that fungal contamination was common, will all 13 (100%) drywall samples contaminated heavily with the fungi Neosartorya hiratsukae. Drywall panels were also contaminated with Chaetomium (11 panels or 85%), Penicillium chrysogenum (9 panels or 68%), Cladosporium cladosporoides (8 or 62% panels), Stachybotrys chartarum (7 panels of 54%). In most cases, heavy fungal growth was noted on drywall 3 to 14 days after the drywall was wetted (Andersen, Dosen et al. 2017) .
 

While mold require water for growth, many mold spores can remain dormant for long conditions when very dry and resume rapid growth and mycotoxin production when wetted.  A Texas study reported that spores of several common molds including Stachybotrys charatarum, Penicilum chrysogenum, and Chaetomium globosum were viable after they were inoculated on dry drywall and stored for 8 months to 3.3 years at 20-60 relative humidity.  After a dry period of as long as 3.3 years, all 3 species were able to resume rapid growth and mycotoxin production when wet.

Drywall often supports heavy mold growth which is not easily visible from the outside.  If water damage to drywall is suspected, the drywall should be tested for water damage by such means as moisture meters/ infrared cameras, and for mold damage by fiberoptic devices (to observe mold growth while making only a small hole in the drywall).  Water damaged drywall should be removed and replaced to prevent heavy growth of mold and bacteria.
 

References / Sources

Andersen, B., et al. (2017). “Pre-contamination of new gypsum wallboard with potentially harmful fungal species.” Indoor Air 27(1): 6-12.

Murtoniemi, T., et al. (2003). “The relation between growth of four microbes on six different plasterboards and biological activity of spores.” Indoor Air 13(1): 65-73.

Wilson, S. C., et al. (2004). “Culturability and toxicity of sick building syndrome-related fungi over time.” J Occup Environ Hyg 1(8): 500-504.

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