How to Clean Concrete Floors

Match the cleaner to your floor

Before you fill a bucket, figure out which floor you have. If water beads on the surface, it is sealed. If it soaks in and darkens the concrete, it is bare.

Two patterns run through that table. Anything decorative wants a neutral pH. Anything bare and porous wants as little standing water as you can get away with.

Why pH-neutral cleaner matters

A pH-neutral cleaner sits in the middle of the scale, around 7, so it lifts dirt without chemically attacking the floor. That middle ground is the whole point on sealed and polished concrete.

Acidic products are the real danger. Vinegar, citrus cleaners, and acid-based bathroom or brick cleaners react with the surface and etch it, leaving dull, cloudy spots you cannot buff out. Concrete Network lists ammonia, citrus, bleach, vinegar and pine cleaners among products that can react with the concrete and etch the surface. On polished floors, that etching kills the gloss.

The other end causes trouble too. Strong alkaline degreasers and TSP strip sealer and wax over time and can lighten stained color. Dish soap seems gentle, but it holds grease in suspension, so on a floor it dries to a thin film that hazes the surface and grabs new dirt. If you use it at all, use a few drops and rinse. Cleaning to prep for a fresh finish? Read our concrete floor sealing guide before you reseal.

Routine cleaning, step by step

Weekly upkeep is fast once the floor is finished, and the order matters more than the products.

1. Dry dust-mop or vacuum first. Grit is the enemy. Loose sand acts like sandpaper underfoot and scratches a polished surface, so pull it up before any water touches the floor.
2. Mix a pH-neutral cleaner with warm water at the dilution on the label. Do not eyeball extra cleaner; more soap means more residue.
3. Damp-mop, do not flood. Wring the mop so it is damp, not dripping, and work in overlapping passes. Wondering how to mop concrete floors without streaks? A flat microfiber mop leaves far less residue than a string mop.
4. Rinse if the label says to. No-rinse neutral cleaners skip this. Anything sudsy needs a clean-water pass so no film dries on top.
5. Dry the surface. Wipe wet spots or let good airflow finish. Standing water leaves streaks and, on bare concrete, dark rings.

Do this weekly in busy rooms and every couple of weeks in quiet ones. Mats at the doors cut how often you mop at all.

Cleaning a concrete garage or basement floor

Garage and basement slabs are a different animal. They are usually bare or lightly sealed, they see tires, road salt, and dropped tools, and they can handle stronger cleaning than a polished floor.

Start dry: sweep or shop-vac the whole floor, corners included. For general grime, a concrete-safe degreaser mixed with warm water and worked in with a stiff-bristle brush does most of the job. CMHA's TEK 08-02A adds a detail worth knowing on a cold slab: "Heated water is useful on greasy surfaces or during cold weather." Rinse toward a floor drain or out the door, then let it dry fully.

Basements add moisture problems. That white, powdery film is efflorescence, and a 50/50 white vinegar and water mix handles it on bare concrete (the one spot vinegar earns its place, since there is no sealer to etch). For a musty smell, an enzymatic cleaner breaks down what feeds the odor. If you find actual mold, an antimicrobial treatment plus fixing the moisture source matters more than any scrub, because a slab that keeps wetting will keep growing it back. Basement concrete floors covers the moisture side properly.

Removing oil, grease and rust stains

Set expectations first, and the reason is physical rather than pessimistic. Concrete is porous, so a spill soaks in on contact. The National Research Council of Canada's building digest Removal of Stains from Concrete Surfaces puts the governing rule simply: "A stain that has penetrated deeply into the concrete will be more difficult to remove." On a stain that has sat in bare concrete for years you are usually lightening rather than erasing, and that is a normal outcome, not a failed attempt.

Oil and grease are not the same problem

This is the distinction almost every cleaning article misses, and it decides which method works. The same NRC digest reports that linseed, soybean and tung oils "penetrate concrete surfaces easily", while "Grease does not penetrate into concrete."

So grease is a surface problem: degreaser, hot water, a stiff brush and some effort will get it, because there is nothing to draw back out. Oil is a depth problem, and scrubbing the surface of an oil stain mostly moves it around. That is why the two need different treatments and why people conclude that "nothing works" after attacking an oil stain with the grease method.

Fresh oil: absorb before you scrub

Speed matters more than product choice. The NRC digest's advice for oils is immediate attention: the spill "should be mopped off with a cloth or a paper towel", then covered with a dry absorbent such as hydrated lime, fuller's earth or whiting. Cat litter, sawdust and baking soda work on the same principle and are what most garages actually have. Leave the absorbent on the spot for a day or two, sweep it up, then follow with a concrete-safe degreaser and a stiff brush.

What you are doing is competing with the slab for the oil. Every hour the spill sits, more of it is below the surface and less of it is available to an absorbent.

Set-in oil: the poultice method

Once the oil is in the pores, you need to pull it back out rather than wash it off. That is a poultice, and it is the one technique on this page worth learning properly. CMHA's TEK 08-02A, Removal of Stains From Concrete Masonry, defines it as "a paste made with a solvent or reagent and a finely powdered, absorbent, inert material", and the mechanism is that "The solvent dissolves the staining substance and absorbs it into the poultice".

In practice: mix a degreaser or solvent with an absorbent powder into a paste about the consistency of peanut butter, spread it over the stain a quarter inch thick and past the edges, cover it with plastic taped at the edges, and leave it a day or two. The plastic is not optional. It stops the solvent flashing off, which is what gives the paste time to work. Scrape it off dry, rinse, and repeat if the stain lightened but did not clear. Two or three cycles on an old stain is normal.

One warning from the same TEK that catches people improvising: portland cement, whiting, ground limestone and hydrated lime must not be used as the powder if your solvent is acidic, because the acid attacks the powder instead of the stain.

Rust, and why acid is a last resort

A paste of lemon juice and salt left for a few minutes lifts light rust from bare concrete. For anything deeper the usual answer is an acid, and that is where care is needed, because the acid does not distinguish between the stain and the floor.

CMHA is blunt about it: "Even weak acids should be used only as a last resort", because acid works "as it dissolves the cement matrix of the masonry beginning at the surface". The NRC digest says the same of rust specifically, noting that muriatic and phosphoric acids "impart a slight roughness to the concrete surface". You are trading a stain for a patch of etched, more porous, slightly different-colored floor, which on a visible slab can be the worse outcome.

On sealed, stained or polished floors, skip acid entirely and ask the sealer manufacturer for a compatible product. Etching a decorative floor is not reversible with cleaning. If the floor is bare and you decide an acid is warranted, dilute by pouring acid into water and never the other way, and wear gloves and eye protection.

For color work, painting or refinishing after a good clean, see our guides on polished concrete, stained concrete and painted concrete floors. If the surface is beyond cleaning, concrete floor resurfacing covers what an overlay can and cannot hide. Planning a new pour instead? Estimate materials with our concrete floor calculator. Living with one day to day is covered in concrete floors in the house.

Pressure washing concrete

Outdoors, a pressure washer does in twenty minutes what a brush and degreaser take an afternoon to do. Indoors it is almost always the wrong tool: the overspray makes a bigger mess than the floor started with, and there is nowhere for the water to go.

Concrete Network recommends a machine rated at least 3000 psi and 4 gpm, which handles nearly all routine cleaning, and holding the nozzle about 12 inches off the surface. Flow matters as much as pressure: gallons per minute is what carries the loosened dirt away, and a high-psi, low-flow machine mostly pushes grime around.

Three cautions worth taking seriously:

• Pressure erodes the paste. The mechanism is the same one that makes acid a last resort: you are removing the fine cement at the surface and exposing the sand and stone under it. Too close, or too long in one spot, and you leave a permanently rougher, lighter patch.
• Test first on anything decorative. Concrete Network notes that older, stamped or stained concrete "may respond differently to the powerful stream of water", so find an out-of-the-way square foot before you start on the visible middle.
• Mind the runoff. Where the water goes matters once you have added a degreaser to it, and local rules on discharge to storm drains vary. Check before you wash a floor covered in motor oil toward the street.

A wheel-mounted surface cleaner, the walk-behind attachment that looks like a lawn mower, is worth renting for anything larger than a parking space. It keeps a constant standoff distance, which is exactly what stops the streaking and the eroded patches a hand wand leaves. For patios, porches and pool decks specifically, outdoor concrete floors covers the finishes that change what you can safely use.