New concrete needs time to cure before it can take pressure washing. High pressure too soon can etch the surface, expose aggregate, and damage the cure, so the age of the slab is the first question to ask.
How long to wait
Concrete gains strength over weeks, not days. Pressure washing a slab that is only days old can mark it. A low-pressure rinse is safer for fresh concrete; reserve higher pressure and surface cleaners for concrete that has cured.
Has it been sealed?
If the concrete was sealed, the sealer changes the approach — some sealers react poorly to pressure or certain cleaners. Know whether a sealer is down before you wash.
What is the stain?
Mud rinses off gently. Form release, curing compound, and efflorescence need specific treatment, not pressure. Identify the stain before you choose the method.
Five-minute self-check
- How old is the slab? Note the pour date.
- Has it been sealed, and with what?
- Is the stain mud, or a construction chemical?
- Check the joints for sand that could wash out.
- Confirm what the clean needs to achieve (inspection, prep for seal).
Related reading
See our driveway cleaning and concrete sealing pages, and our post on a muddy sidewalk before inspection.