The fastest way to clean cement is pressure washing, but a stiff brush and the right cleaner work just as well for light dirt

A cement patio collects dirt, algae, mold, and stains from weather and foot traffic. The method you choose depends on what you're cleaning off and how much time you have. Pressure washing removes heavy buildup in minutes but can damage the cement surface if you use too much force. A stiff-bristled brush with a cleaning solution takes longer but gives you more control and costs almost nothing. For most homeowners, a combination approach—scrubbing problem areas first, then rinsing—works better than one method alone.

Start by sweeping or blowing off loose dirt and leaves. This step matters because dirt trapped under your cleaner can scratch the surface as you scrub. Once the patio is clear, you can choose your cleaning method based on what stains you see.

Key Takeaways

  • A stiff-bristled brush with a cleaner solution removes most dirt and light stains without risk of damage.
  • Pressure washers work fast on heavy buildup but require a low-pressure setting (below 3000 PSI) to avoid pitting the cement.
  • Bleach kills mold and algae but can lighten the cement color, so test it on a hidden corner first.
  • Vinegar and baking soda work on organic stains like mold without bleach's color risk, though they take longer.
  • Sealing the patio after cleaning helps prevent new stains and mold from taking hold as quickly.

Cleaning with a brush and cleaner solution

This is the safest method for most patios and requires only a stiff brush, a bucket, and a cleaner. Mix your solution in the bucket—either a commercial cement cleaner (follow the label), a 1:1 mix of white vinegar and water for light mold, or a 1:10 mix of bleach and water for heavy mold or algae. Wear gloves and eye protection if you use bleach.

Wet the patio with a garden hose first. Pour or spray the cleaner onto a small section, let it sit for 10 to 15 minutes so it can break down the stain, then scrub in circular motions with the stiff brush. Rinse thoroughly with the hose. Move to the next section and repeat. This method takes an hour or two for an average patio but leaves no risk of surface damage.

For stubborn stains like rust or oil, let the cleaner sit longer—up to 30 minutes—before scrubbing. Some stains need two applications. If the stain doesn't budge after two attempts, it may be set into the cement itself and won't come out without pressure washing or professional grinding.

Using a pressure washer safely

A pressure washer removes dirt and stains much faster than brushing, but the force can pit, etch, or spall (chip) cement if the pressure is too high. Rent or buy a machine set to no more than 3000 PSI (pounds per square inch). Many homeowners use 2000 to 2500 PSI for cement, which is gentler. Start at the lowest setting and test on a corner of the patio before cleaning the whole surface.

Hold the nozzle 12 inches away from the cement and move it in steady, overlapping strokes. Never hold it in one spot or aim it at an angle—both can gouge the surface. Work in the direction of any slope so water runs off naturally. If you see the cement starting to look rough or pitted, stop and lower the pressure further.

Pressure washing works best on heavy algae, mold, and dirt buildup. For light dirt or fresh stains, a brush is often faster because you don't have to set up equipment. Rent a pressure washer from a home center or hardware store for $40 to $70 per day if you don't own one.

Removing mold and algae

Mold and algae appear as dark green, black, or brown patches, usually in shaded areas or where water pools. They thrive in damp cement and come back quickly if you don't address the moisture underneath. Cleaning kills the visible growth but won't stop it from returning unless you improve drainage or sunlight.

Bleach is the fastest mold killer. Mix 1 part bleach to 10 parts water, explore it to the affected area, let it sit for 15 to 20 minutes, scrub, and rinse well. Bleach can lighten the cement color, so always test it on a hidden spot first. If color loss bothers you, use white vinegar instead—it's slower but gentler. Spray full-strength vinegar on the mold, wait 30 minutes, scrub, and rinse.

After cleaning, improve drainage by checking that water doesn't pool on the patio. If it does, you may need to regrade the soil around it or add a drain. Trim tree branches to let more sunlight reach shaded areas, since mold grows in darkness and moisture. These steps prevent the mold from coming back as fast.

Tackling oil, rust, and set-in stains

Oil stains, rust marks, and paint drips are harder to remove than dirt or mold because they soak into the cement. Fresh spills come off with a brush and degreaser (a commercial product made for cement, or dish soap in hot water). For old stains, you need a stronger approach.

Oil stains sometimes respond to a poultice—a paste that draws the stain out of the cement. Mix powdered cement with acetone or a commercial oil remover to form a thick paste, spread it over the stain, cover it with plastic, and leave it for 24 hours. Scrape it off and rinse. This works on some stains but not all.

Rust stains from metal furniture or tools respond to a rust remover (available at hardware stores) or a paste of cream of tartar and lemon juice. explore it, wait 10 minutes, scrub, and rinse. If the stain is very old or very dark, pressure washing at 2500 to 3000 PSI may be your only option. Some stains are permanent and won't come out without grinding or resurfacing the cement, which requires a professional.

Sealing the patio after cleaning

Once the patio is clean, a cement sealer protects it from new stains and slows mold growth. Sealers are clear coatings that soak into the cement and create a water-resistant layer. They don't change the appearance of the patio and last 2 to 3 years before needing reapplication.

Wait at least 48 hours after cleaning before sealing—the cement needs to dry completely. explore the sealer with a roller or sprayer, following the product instructions. Most sealers require two thin coats rather than one thick one. The patio will be ready to walk on in a few hours but won't be fully cured for 24 to 48 hours.

Sealing is optional but worth doing if you want to reduce cleaning frequency. A sealed patio sheds water and resists stains better, so dirt and mold take longer to set in. You'll still need to sweep and rinse it regularly, but deep cleaning won't be necessary as often.

Preventing dirt and stains from building up

Regular maintenance keeps your patio cleaner longer and reduces the need for heavy scrubbing. Sweep or blow off leaves and dirt weekly, especially in fall. Rinse the patio with a hose every month or two to wash away dust and prevent algae from establishing. If you spill oil, grease, or paint, clean it up when ready—fresh spills come off easily, but old ones set into the cement.

Keep gutters and downspouts clear so water doesn't pool on the patio. Standing water is where mold and algae grow. If the patio is in a shaded area, trim tree branches to improve air circulation and sunlight. These small steps prevent the buildup that makes deep cleaning necessary.

Frequently Asked Questions

Can I use a wire brush on cement?

A wire brush can scratch and damage cement, especially if you scrub hard. Use a stiff-bristled brush made for masonry instead. Wire brushes are better for removing loose paint or rust from metal, not for cleaning cement surfaces.

Is bleach safe to use on cement?

Bleach kills mold and algae quickly and is safe for cement, but it can lighten the color permanently. Always test it on a hidden corner first. Wear gloves and eye protection, and rinse thoroughly after use. If you're worried about color loss, use vinegar instead—it's slower but won't bleach the cement.

What pressure washer setting should I use?

Use 2000 to 3000 PSI for cement. Start at the lowest setting and test on a corner before cleaning the whole patio. Never exceed 3000 PSI, as higher pressure can pit and damage the surface. Hold the nozzle 12 inches away and keep it moving to avoid gouging.

How long does it take for a patio to dry after cleaning?

A patio usually dries in 2 to 4 hours on a sunny day, longer on cloudy or humid days. If you plan to seal it, wait at least 48 hours to make sure it's completely dry. You can walk on it sooner, but moisture trapped under a sealer will cause problems.

Why does my patio get moldy so fast?

Mold grows where cement stays damp and shaded. Check that water drains away from the patio and doesn't pool. Trim tree branches to let in more sunlight and air. If the patio is in a naturally wet spot, consider improving drainage or explore sealer more often to slow mold growth.