Mold under your artificial grass: how to tell, and when the turf has to come up

Surface mold grows on the organic layer sitting in the infill, exactly like the black patches or musty smell already covered elsewhere on this site, and it is reachable with a brush and a rinse. Mold under the turf grows on the underside of the polyurethane or latex backing, or in the aggregate base beneath it, where moisture has been trapped for long enough with no airflow to dry it out. That happens when the base was built without proper drainage, when a low spot holds water against the backing, or, less often, when the base was never given time to dry before the turf was laid over it.

A musty or mildewy smell that is strong but shows little or no matching discoloration on the infill surface is the main clue; surface mold you can usually see once you part the fibers, while mold underneath you mostly smell. Press on the turf in the suspect area after a dry week; if it still feels damp with no obvious surface cause, moisture is likely trapped below. Lifting an accessible edge or corner, where possible, and looking at the underside of the backing confirms it directly.

Confirmed surface mold is handled the standard way: power brush, flush, turf-safe treatment, antimicrobial. Mold confirmed under the backing or in the base is a different job: the affected section of turf has to be lifted so the backing can be cleaned and dried and the base inspected, and if trapped water is the cause, the drainage in that section needs correcting before the turf goes back down. That work is a base repair, done with our sister company, not a surface clean, and we will tell you plainly which one your yard needs.

Once drainage is corrected, mold underneath a properly built, well-draining base is rare. Keep the surface infill clean so it is not adding its own moisture and organic load on top of a marginal base, and have any spot that stays oddly damp after a dry week checked before it becomes a bigger job.