Question: Our stucco house was built in late 2004 and within the last month or so we’ve notice some white fuzzy fungus developing on the (east-facing) concrete slab of a small exterior alcove that connects the kitchen to the garage.
I tried scrubbing it with a warm water and bleach solution and it went away briefly, but now it’s reappearing at a faster rate and spreading. What is an eco-safe but effective fungicide to use? — Debbie
Answer: From licensed general contractor Alon Toker of Mega Builders in Chatsworth:
The "white fuzzy fungus" described might not be a fungus at all. Rather, it might be efflorescence (salt left behind when water evaporates). I would suggest that you contact a competent concrete finisher to take a look and address the issue. If it turns out that indeed you are dealing with a fungus, I would recommend contacting an hygienist to test and identify the fungus and prescribe a treatment.
(Photo: Image of efflorescence from Wikipedia)