Ask a SoCal contractor: What’s up with this ‘white fuzzy fungus?’

Written By: Kathy Price-Robinson - Feb• 19•08

Efflorescencewikipedia_2Question: 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.

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(Photo: Image of efflorescence from Wikipedia)

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One Comment

  1. Spectrum Builders says:

    The “white fuzzy fungus” described might not be a fungus at all. Rather, it might be efflorescence
    This is a fungal growth, and is condition spawned by hydrated lime used in the cement to make it pallatable (workable). After the initial curing process, when water is reintroduced and the surface experiences saturation and absorbtion to a degree, it triggers the lime and growth occurrs. Look for a root cause allowing or promoting the saturation, dry-brush the affected surface then wipe with a damp cloth. Sometimes a muriadic acid solution will help like Tilex. Then consider the application of a clear sealer or waterproofing material, I would recommend use a “Breathable” Product to negate future discoloraiton and yellowing. Once neutralized, a paint coating can also be applied to the suface, but be forewarned, residual moisture behind the suface would result in bubbles, blistering and flaking of the coating.
    Barry, Public Adjuster

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