Mold in green roof
installations

Questions and answers from the GMA Techline

Mold in green roof
installations

Recently there has been a greater demand for sustainable projects in Southern California, so I was glad [to read the article in Geosynthetics magazine] “Geosynthetics: The science that makes green roofs work.”

I am curious if there are any reports or case studies about mold growing inside the green roof’s drainage layer and how the designers could mitigate this situation. Given the right combination of moisture and fertilizers, even in dry arid climates, I imagine mold could be problematic.

(Lukas | California)

Lukas,
Neat question and, yes, various organic materials have grown within geotextile filters and even clogged the drainage pipes that they enclose. A major issue is “ochre,” which grows when the drainage system is in a cyclic wet-then-dry location. High iron oxide content soils also encourage growth. We have six recorded geotextile filter failures in this regard. The remedy is high-pressure flushing and/or chemical (biocide) cleaning.

I suspect that mold is a subset of ochre but
we do not have specific case histories in
this regard.

Hope this helps,

Bob Koerner | GMA Techline