Mold in Shower: How to Clean Grout, Caulk and Prevent It

Showers give mold everything it needs. The Department of Energy's Building America Solution Center says baths and showers release a half pint of water for every 5 minutes the shower is running, and that with no exhaust fan, this moisture can lead to mold and mildew on tile, walls, and ceilings.

The EPA says a little condensation, in a bathroom or around a window sill, can be enough for mold to grow. TDLR adds that bathtub or showers corners and joints, including tile crevices, are more susceptible to mold growth. UF Extension notes mildew can grow on soap scum and moisture, which is why regular cleaning matters.

Black mold in a shower is usually just dark-colored mold or mildew on grout and caulk. Color doesn't tell you much, and you don't need to identify it. The CDC says you do not need to know the type of mold; remove it either way. The EPA says that in most cases, if visible mold growth is present, sampling is unnecessary.

Mold can bother some people. The CDC says it can cause a stuffy nose, sore throat, coughing or wheezing, burning eyes, or skin rash in some people, and that people with asthma or mold allergies may react more. If you have health concerns, talk to a doctor; a mold test can't diagnose illness. For more, see our black mold guide.

This is for typical shower mold: grout, tile, glass, the tub surface and the surface of caulk.

What you need: a scrub brush or old toothbrush, detergent or bathroom cleaner, a spray bottle, a towel or squeegee, and protective gear.

1. Ventilate. Turn on the exhaust fan and open the window if there is one. If you use bleach, the EPA says to always ventilate the area and exhaust the air to the outdoors.
2. Protect yourself. For small areas, the EPA's minimum is gloves, an N-95 respirator, and goggles/eye protection. With bleach, choose gloves made from natural rubber, neoprene, nitrile, polyurethane or PVC, and goggles that do not have ventilation holes.
3. Pick one cleaner.
   • Detergent and water: the EPA's default is to scrub mold off hard surfaces with detergent and water, and dry completely.
   • Vinegar: Oregon State Extension suggests a half-water, half-vinegar solution.
   • Bleach: the CDC says no more than 1 cup of household laundry bleach in 1 gallon of water. UF Extension recommends cleaning the shower with chlorine bleach, with the window open and not mixing it with any other cleaning product.
4. Scrub the grout lines and corners. The goal is to remove the mold, not just bleach the color out. The EPA says it is not enough to simply kill the mold. It must also be removed.
5. Rinse and dry. Squeegee or towel the walls.
6. Check the caulk. If dark spots remain inside or behind the caulk after scrubbing, it's time to replace it (next section).

Never mix cleaners. The CDC says never mix bleach with ammonia or other cleaners, because it makes a poisonous gas. Bleach plus an acid such as vinegar gives off chlorine gas, according to the Washington State Department of Health. The department lists toilet bowl cleaners and some glass and window cleaners among acid products, so rinse well and air out the room before switching products. See our vinegar vs bleach for mold guide.

Grout and caulk behave differently.

Table: cleaning mold on grout and caulk.

Why you can't caulk over mold

The EPA says do not paint or caulk moldy surfaces. Bob Vila explains the practical reason: moldy caulk doesn't just go away because you cover the mold with new caulk, and the mold continues to grow and spread inside the walls.

How to replace moldy caulk

1. Remove all the old caulk. Bob Vila's guidance is to soften it with a caulk remover, cut along its top and bottom edges with a utility knife, then peel and scrape the rest away (Bob Vila).
2. Clean the gap. Scrub any mold in the joint using the steps above, wearing your gloves and goggles.
3. Let it dry fully. Bob Vila notes that caulk won't adhere to a wet surface. Running the fan or a small dehumidifier helps.
4. Use a bath-rated, mold-resistant caulk. Bob Vila recommends checking that the label says it is for kitchens and baths; clear caulks with special inhibitors that protect against mold and mildew are a good option.
5. Let it cure. Bob Vila says to wait at least 24 hours before regular shower use, or follow the product label.

Bob Vila also says a thorough caulking job should last at least a year, so plan to check your caulk every year.

The EPA's advice is direct: run the bathroom fan or open the window when showering. For bathrooms where mold keeps coming back, the EPA says increasing ventilation and cleaning more frequently usually keep it in check.

Tips for the fan:

• Make sure it vents outside. Oregon State Extension advises venting bathroom exhaust fans outside, not into the attic (OSU Extension). A fan dumping steam into the attic just moves the mold problem.
• Leave it running after you shower until the mirror and walls clear.
• Consider a quieter, efficient fan. The DOE Solution Center notes that ENERGY STAR-rated exhaust fans meet performance criteria for energy efficiency and sound levels.
• No fan? Open the window and keep the bathroom door open after showering.

• Squeegee or towel the walls. UF Extension says to dry/squeegee off the shower walls after using the shower. TDLR says to use a towel or squeegee to dry off wet surfaces after bathing, especially corners and joints.
• Clean regularly. UF Extension says to clean showers/tub regularly so mildew can't grow on soap scum.
• Spread out the curtain. UF suggests stretching the shower curtain along the rod so it will dry instead of sticking together.
• Hang towels to dry where air circulates.
• Shorter, cooler showers. UF Extension notes that steam wets the ceiling and the walls.
• No bathroom carpet. The CDC says don't use carpet in places like bathrooms or basements that may have a lot of moisture.
• Keep the house dry. The EPA recommends indoor humidity below 60 percent (ideally between 30 and 50 percent). In humid parts of Texas, a dehumidifier for mold can help in a bathroom without a fan.

Surface mold is normal. These signs point to something behind the tile:

• Mold returns within days of a thorough cleaning
• Loose tiles, cracked grout or soft spots in the wall
• Mold or stains on the other side of the shower wall, or on the ceiling below an upstairs bathroom
• Peeling paint or a musty smell outside the shower

That can mean a leak in the shower valve, pan or supply line. The EPA warns that mold may be hidden in places such as the back side of dry wall and inside walls around pipes, and suggests hiring an experienced professional if you suspect hidden mold. Our mold on walls guide covers what happens when drywall is involved.

Size matters. The EPA says you can usually clean a patch less than about 10 square feet (less than roughly a 3 ft. by 3 ft. patch) yourself. Larger areas call for professional guidance. In Texas, TDLR says areas of visible mold less than 25 contiguous square feet can, in most instances, be cleaned by people who aren't licensed.

Cost. Fixr puts bathroom mold removal at $500 to $1,500 (updated Aug 2025), and notes mold behind a tub or vanity can raise the cost substantially. See our mold remediation cost guide.

Who to call. For removal, use a licensed mold removal company. If you want an assessment first, use a separate mold testing company; Texas law says a license holder may not perform both mold assessment and mold remediation on the same project. Renters should tell the landlord in writing; TDLR suggests following up conversations with a letter to the landlord. See mold in your apartment in Texas. Check any company with our license check or browse companies in Austin and across Texas.