How to Clean Algae Off Concrete with Pressure Washing

All of the rain we receive in the Pacific Northwest creates a welcoming climate for the green slime to grow and spread. Not only is it unattractive, but algae can also be dangerous as it makes the concrete slick and creates a potential hazard for slips and falls.

Though there are many ways to address algae, pressure washing is the best solution to clean algae from your driveway or patio.

Power washing stamped concrete is the best way to remove tough stains such as algae, leaf stains, and tire marks. Other stains like oil, grease, and antifreeze are common on concrete driveways, and can be removed with a power washer and either mild detergent or an alkaline degreaser.

In this blog, we will cover the 4 steps to cleaning algae off concrete with pressure washing, and how to prevent it from happening again:

1. Pressure Washing Concrete
2. Treating Concrete Surface
3. Sealing concrete after pressure washing
4. Maintenance and Prevention

Your concrete may seem rock solid and impervious to all sorts of threats.

However, concrete is porous and vulnerable to damage from things like algae, lichen, and moss. These organisms can erode your concrete and dramatically shorten its lifespan.

To most effectively clean away the algae, high water pressure can force out any growth that has gotten down in the pores of your concrete. After power washing the concrete, algae will have a harder time returning than if you simply used a broom and a little soapy water.

Once the power washing is complete and your concrete looks great, you may want to then treat it with a bit of chemical solution.

Use a non-toxic solution to put the finishing touches on your cleaning job. Oxygen bleach is one solution that many reach for. Look for a 100% organic oxygen bleach to make sure that you are good to the surrounding plants and animals.

Alternately, you might sprinkle a liberal amount of baking soda on the affected area. Then, pour or spray white vinegar. It may be a little smelly, but it is safe and effective.

After cleaning the concrete surface with a pressure washer, lay down a concrete sealant.

We strongly recommend using 2 coats only if necessary. Adding too much sealer can create moisture-related problems, such as efflorescence – the salt residue that surfaces from concrete and mortar in wet conditions – and color variations.

The first coat will soak into the pores and do the job for providing protection. The second coat is optional but is desired for an elegance effect. If you’re going for a shiny gleam from your driveway or patio, use a solvent-based sealer. If you want a more natural look, use a water-based sealer.

Stay off the concrete driveway, patio or stairs for 24 hours. Also, make sure that the weather is dry before even starting this step.

Once your concrete is clean and resurfaced, you can work to avoid future algae problems with regular cleaning and increased sun exposure. For regular cleaning, you can use a simple push broom or even a garden hose to wash away debris.

Be aware of particular times of year when debris is likely to accumulate. Many homeowners find that autumn is a bad time for leaves, nuts, and other detritus to accumulate.

You might want to trim back bushes or tree limbs to increase sun exposure. While that may not do much good in the Pacific Northwest winter, it will help. If the problem is on a patio, you might move patio furniture, which may be providing cover for algae.

Consult GWC Decorative Concrete to eliminate algae, moss, and mud from your concrete surface.

Since 1997, our team of friendly, experienced, and professional concrete contractors have provided exceptional service to homeowners in the Portland area. Learn more about our pressure washing and sealing services.