How to clean concrete floors: sealed, polished, painted or bare

Step by step: how to clean concrete floors

Safety first. Wear gloves and eye protection with TSP or any heavy-duty cleaner, and follow the label. Never mix bleach with ammonia or acidic cleaners, and ventilate basements and garages while you work.

1. 1

   Check whether the concrete is sealed

   Drip a few drops of water on the floor in a low-traffic spot. If they bead up, the floor is sealed, polished or coated; if the concrete darkens and soaks the water in, it is unsealed or the seal has worn off. This decides how much water and how strong a cleaner you can use.

2. 2

   Remove all loose dirt

   Sweep with a soft broom, run a microfiber dust mop or vacuum the whole floor. On bare concrete, a shop vacuum also pulls dust out of the pores. Grit left on the surface scratches sealers and turns into mud when you mop.

3. 3

   Mix a mild cleaner

   Fill a bucket with warm water and add a pH-neutral floor cleaner at the label rate, or about a teaspoon of dish soap per gallon. Fill a second bucket with plain water for rinsing. Neutral cleaners are gentle on sealers and polished surfaces.

4. 4

   Mop in sections

   Work in 4 by 4 foot sections, starting at the far wall. On sealed or polished concrete, use a well-wrung microfiber mop so the floor is only damp. On unsealed concrete, scrub stained or dusty areas with a stiff nylon brush as you go.

5. 5

   Rinse with clean water

   Go over each section with a mop dipped in the rinse bucket and wrung out. Cleaner left on the floor dries to a dull film that holds new dirt. Change the rinse water when it turns cloudy.

6. 6

   Dry the floor completely

   Squeegee standing water toward a floor drain or pick it up with a wet vacuum, then run fans or a dehumidifier. Basement concrete that stays damp can grow mildew, so aim for a fully dry floor within a day.

7. 7

   Spot treat stains

   Blot fresh spills right away, especially oil, wine and rust, which soak into bare concrete. For set-in oil stains, use the methods in our oil stain guide; for stubborn grime on unsealed concrete, scrub with a TSP solution mixed per the label and rinse well.

How to clean each type of concrete floor

Clean sealed, polished and coated concrete gently, and save scrubbing and stronger cleaners for bare concrete. Sherwin-Williams describes the water-drop test above and recommends pH-neutral cleaners (pH 6.5 to 7.5) for routine cleaning.

Sherwin-Williams also notes that bleach and ammonia can etch the surface and damage a finish, and that painted concrete should not get too wet because water affects the paint’s grip. Simple Green’s method for sealed floors is the same idea: a light mist of cleaner, a well-wrung mop, and drying before anyone walks on it.

How to clean a damp or musty basement concrete floor

Fix the moisture first, then clean. A concrete floor that keeps getting damp will smell musty again no matter how often you wash it.

• Scrub any mildew off with detergent and water and dry it completely; the EPA gives this as the basic method for mold on hard surfaces.
• Keep indoor humidity below 60 percent, ideally 30 to 50 percent, with a dehumidifier. The EPA notes that materials dried within 24 to 48 hours usually do not grow mold.
• If mold covers more than about 10 square feet, the EPA’s mold cleanup guide suggests reading its full guidance or getting a professional. Moldy carpet or rugs laid on concrete may have to be thrown out.
• For lingering smells after cleaning, see our musty smell guide.

When to reseal or recoat a concrete floor

Reseal when water no longer beads on the surface or the floor looks chalky and stains easily. That is the sign the sealer has worn through in traffic areas.

Sherwin-Williams gives rough lifespans of up to 20 years for polished concrete, 5 to 10 years for epoxy or polyurea coatings, and repainting every 3 to 5 years for painted floors. Topical sealers on stained concrete in busy rooms often need a fresh coat sooner; check the product label. Clean thoroughly and let the slab dry before any recoat, or the new coat will not bond.

Mistakes to avoid

• Using vinegar or other acids on polished or sealed concrete, which can etch and dull it.
• Mopping without vacuuming first, which grinds grit into the sealer.
• Skipping the rinse, which leaves a sticky film that makes the floor look dirty quickly.
• Leaving a basement floor wet overnight, which invites mildew.
• Pressure washing indoor concrete, which floods walls and drains.