Mold and mildew on a rug

Where it starts

Mold and mildew need moisture and time. The usual causes are a potted plant standing on the rug, a leak or spill that soaked through to the floor, a damp basement, or a rug stored rolled up in a humid room.

The U.S. Environmental Protection Agency advises drying wet materials within 24 to 48 hours to prevent mold growth. After that, the risk rises quickly, especially under the rug where air cannot reach.

Signs to look for

A musty smell that returns after the rug is aired out is often the first sign. Look on the back of the rug and on the floor or pad beneath it for gray, green or black spots, or a stain in the shape of a pot or puddle.

Colors that have bled or a ring that stays darker than the rest of the rug also point to water that sat too long.

Test a handmade rug for dry rot

Most hand-knotted rugs have a cotton foundation under a wool pile. Long dampness can rot the cotton while the wool on top still looks fine. This is called dry rot.

To test, fold a small section of the rug back on itself over the suspect area and press gently. Cracking sounds, stiffness or fibers that break mean the foundation is weak. Do not keep folding a rug that cracks, because it can tear.

Rotted areas cannot be made strong again by cleaning. A restorer can sometimes stabilize or reweave small areas, so have it looked at before deciding.

What to do after a leak or flood

Lift the rug off the wet floor right away and get air under it. Blot out as much water as you can with towels, then dry both sides with fans in a ventilated room, out of direct, strong sun that can fade the colors.

A rug soaked by flood water or sewage should be washed by a cleaner who washes area rugs in a plant, not cleaned in place. Tell the cleaner what kind of water it was.

Avoid chlorine bleach. It damages wool and silk and strips color. Strong home mold sprays can do the same.

Keeping a rug dry

Put plants on a stand with an air gap, never directly on the rug, and keep a tray under every pot. Check under the rug after any spill that soaks through.

In a basement, run a dehumidifier and check the floor under the rug now and then. Store rugs clean and fully dry, rolled and wrapped in breathable cloth, and off the floor.

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