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If you recently had new concrete installed, such as a patio, driveway, or sidewalk, you may be wondering when you can pressure wash it to remove any dirt or stains. Pressure washing is an effective way to clean concrete surfaces, but it's important to know when it is safe to pressure wash new concrete and follow best practices to avoid causing damage.
What is Pressure Washing and Concrete Curing?
Pressure washing involves using a high-powered stream of water to clean and remove dirt, mold, mud, grime, and more from surfaces like concrete. Pressure washers use an electric or gas motor to power a water pump and attach to a wand nozzle that directs the spray. The pressure is measured in pounds per square inch (PSI) and commercial grade pressure washers typically operate in the range of 500-5000 PSI.
Concrete curing refers to the process of concrete solidifying and gaining strength after initial installation. Concrete goes through a chemical hydration process where the cement and water harden and bind together. Proper concrete curing takes approximately 28 days in normal conditions, but concrete continues to get stronger for months after installation.
Safety Concerns of Pressure Washing Too Early
It can be tempting to want to pressure wash new concrete soon after installation to clean up any dirt from the construction process. However, pressure washing too early on can actually damage the surface of the concrete and create even more work. Here are some key reasons to avoid pressure washing early in the curing process:
- Concrete needs time to properly cure and gain adequate strength before being subjected to pressurized water blasting. Pressure washing too early on can disrupt the curing process and weaken the concrete surface.
- Using too much pressure can damage new concrete surfaces. Even though concrete is durable, the top surface layer can still be etched by high pressure levels early in the curing phase. Most experts recommend 500-1500 PSI for cleaning concrete once fully cured.
- Allowing the pressure washer wand to wander while spraying can etch patterns into the concrete. The nozzle should be held steady and perpendicular to the surface. Letting water pool and concentrate in one area can leave damage marks.
Knowing When It's Safe to Pressure Wash
It's generally recommended to wait at least 4 weeks after new concrete is installed before performing light pressure washing. This allows ample time for the concrete to cure properly. Additional factors to consider:
- Wait until the full 28 day recommended cure time has passed before pressure washing. Concrete reaches about 70% of its full strength at 28 days.
- If sealers were applied, wait until they have fully cured before pressure washing. Sealers protect the surface but need time to bond and harden.
- Pressure washing can be used to remove stains from oil, grease, food, rust and more after full curing. This may take some trial and error to find the right PSI and nozzle setup.
Best Practices When Pressure Washing New Concrete
Once the concrete has cured for at least 28 days, pressure washing can begin safely. Here are some best practices to follow:
- Use a moderate PSI between 500-1000 for residential grade pressure washing. Commercial concrete cleaning may need more pressure, but too much PSI risks surface damage on new concrete.
- Opt for a pressure washer wand with a 15-25 degree fan nozzle. This helps evenly distribute the pressure across a wider area.
- Keep the nozzle about 6-8 inches from the concrete surface while spraying. Get closer for stubborn stains.
- Work systematically in small sections across the concrete, overlapping passes and rinsing thoroughly. This prevents pooled water from concentrating in one spot.
- Allow the concrete to dry fully before applying any concrete sealers. Sealing wet concrete can lead to bonding issues and an uneven seal.
Proper concrete curing followed by moderate pressure washing is key to keeping new concrete looking pristine. While it's tempting to clean up concrete soon after installation, allowing ample curing time and using care when pressure washing will lead to the best results. Avoid potential surface damage by waiting at least 28 days, using lower pressure levels, keeping the nozzle moving uniformly, and rinsing thoroughly. With some patience, new concrete can be safely pressure washed to create a lasting clean surface.
