Wait for new concrete to cure
Fresh concrete is weak at the surface for its first weeks. Hitting it with high pressure too soon can etch the finish, loosen the top layer, or leave permanent wand marks. A common rule of thumb is to wait until the concrete has fully cured, which typically takes several weeks, before any serious pressure washing. Your concrete contractor can confirm the right timing for your pour.
Before that, light rinsing with a garden hose to remove dust is generally fine. In hot, dry Valley summers, fresh concrete dries out quickly at the surface, which is one more reason not to rush aggressive cleaning.
Start with dry cleanup
Construction sites leave nails, screws, wood scraps, wire, drywall chunks and bags. All of that should be swept and picked up before any water is used. Washing over debris just pushes it into corners and drains, and screws can damage equipment.
Mud tracked by trucks and boots should be scraped off while it is dry where possible. Wet mud turns into a slurry that is harder to contain and more likely to stain.
It also helps to ask each trade to clean up after itself as it goes. Masons can rinse splatter while it is still wet, painters can mask walkways before spraying, and concrete crews can wash out away from finished surfaces. Small habits during the job save a lot of effort at the end, because fresh residue lifts far more easily than residue that has hardened for weeks. Put it in the contract or the site rules if you can, since it costs very little during construction and a lot afterward.
Cement slurry and mortar splatter
Cement slurry, the gray residue left by mixers, wet saws and masons, is one of the toughest post-construction messes. Once hard, it bonds to concrete, brick and glass. Pressure alone often cannot remove it without damaging the surface below. It usually needs a scraper for thick spots and a masonry-safe cleaner for the film, followed by a rinse.
Acid-based cleaners are sometimes used on cement film, but they can etch concrete, discolor some stone and harm plants, so they should be applied carefully, neutralized, and kept off sensitive surfaces. On glass, cement splatter should be removed by hand by someone experienced with glass, not by pressure.
Paint overspray and drips
Overspray on concrete, windows and fixtures is common after a repaint. Fresh latex paint drips often come up with a degreaser, some scraping and moderate pressure. Older, cured paint may need a paint remover and several passes. Oil-based paint and stains are harder to remove. Our guide on paint removal from concrete covers this in more detail.
On walls, overspray is usually a matter for the painter, not the pressure washer. Pressure washing a freshly painted stucco wall can damage the new finish. If walls need cleaning, a soft wash at low pressure is the right approach, and only after the paint has fully cured according to the manufacturer's guidance.
Dust on walls, windows and fixtures
Sanding, cutting and grading coat everything in fine dust. On stucco and siding, a low-pressure rinse with a mild solution removes it. Window frames, light fixtures and the house numbers collect it in corners. In the dry months, especially after Santa Ana winds, dust can blow back onto a finished site, so final cleaning is best timed near the end of the job.
Keep in mind that cleaning cannot fix construction damage. Gouges in the concrete, chipped stucco and surface staining from curing compounds may need repair or a refinish rather than a wash.
Wash water and pricing
Construction runoff carries cement fines, paint residue and soil. Los Angeles Municipal Code section 64.70.02 prohibits discharging untreated wash water from paved-surface washing and mobile operations into the storm drain system unless a permit allows it. Block inlets, collect the water, and keep cement residue in particular out of the gutter.
As of October 2026, our calculator lists driveway cleaning at $0.50 per square foot, walkways at $0.55 per square foot, house washing at $0.35 per square foot of exterior wall, building exteriors at $0.30 per square foot, and parking lot and concrete at $0.25 per square foot, with a $195 visit minimum. Bundling saves 5% for two services and 10% for three or more. At Say Wash It we look at the residue first, confirm a flat price, and walk through the results with you, and the instant quote on this page gives a starting figure.
Key points
Wait for new concrete to cure
Fresh concrete is weak at the surface for its first weeks. Hitting it with high pressure too soon can etch the finish, loosen the top layer, or leave permanent wand marks. A common rule of thumb is to wait until the concrete has fully cured, which typically takes several weeks, before any serious pressure washing. Your concrete contractor can confirm the right timing for your pour.
Cement slurry and mortar splatter
Cement slurry, the gray residue left by mixers, wet saws and masons, is one of the toughest post-construction messes. Once hard, it bonds to concrete, brick and glass. Pressure alone often cannot remove it without damaging the surface below. It usually needs a scraper for thick spots and a masonry-safe cleaner for the film, followed by a rinse.