I don’t know if this is where to put this, but didn’t know where else to start, so feel free to remove.
Scenario
The finished basement apartment of a home developed a clean water leak in a water line in the wall. By the time I was called after just a few days, there was obvious mold growing on the painted dry wall and inside the vanity cabinet and a fair amount of it. A mitigation contractor was called out and they determined the grout bed under the tile was 100% saturated and they were worried about mold spores getting into the tile/grout that if not removed, could eventually get a tenant in the apartment sick. My question is if mold spores were washed into the grout/mortar of the tile, could that pose a health risk to someone living in the apartment?
here is what larry said. i reckon his answer is about as good as a mold abatement contractor. that’s the opinion i would listen to, but larry agrees and gave three reasons.
Yes, mold spores that have been washed into grout or mortar can still pose a health risk, depending on the type of mold, the level of moisture present, and the extent of contamination. Here’s why:
1. Mold Growth Potential
Grout and mortar are porous, meaning they can trap moisture and create an ideal environment for mold growth.
If the area remains damp (such as in a bathroom, kitchen, or near plumbing leaks), mold can continue to thrive and release spores into the air.
2. Health Risks
Mold exposure can trigger respiratory issues, allergic reactions, and asthma symptoms, particularly in sensitive individuals.
Some molds, like Stachybotrys chartarum (black mold), produce mycotoxins that may lead to more severe health effects.
Prolonged exposure to mold spores can lead to symptoms such as coughing, sneezing, eye irritation, and skin rashes.
3. Airborne Contamination
Even if mold is embedded in the grout/mortar, disturbances (cleaning, humidity changes, air movement) can release spores into the air, spreading contamination.
4. Remediation & Prevention
Deep cleaning: Use a mold-killing solution (e.g., hydrogen peroxide, vinegar, or a diluted bleach solution) on affected grout.
Sealing: After cleaning, apply a grout sealer to reduce porosity and prevent further moisture absorption.
Moisture control: Use dehumidifiers, proper ventilation, and fix leaks to keep humidity below 50%, preventing mold regrowth.
That’s really helpful, thank you! I should have added one other detail and I’m curious if it would affect the answer at all. The tile is installed over a concrete slab, so would that still contribute to mold growth?
If you have a moisture meter with a non contact function then test the tile several feet away from the water source and take a reading and work your way closer to the water leak. The moisture meter will likely peg out where water is detected under the tile. Be aware that some ceramic tile has some metallic coating which will give you a false positive reading. If you have access look at the subfloor from the basement or crawlspace.