Can You Pressure Wash Hardie Board? How to Clean Hardie Board Siding


When you first install James Hardie siding, it looks bright, clean and stunning. You can easily clean your siding once or twice a year to look its best again after it has endured the outdoor elements.

Many people feel tempted to use a pressure washer to eliminate any dirt, grease and mildew. But can you power wash Hardie siding? Read on to learn how to clean James Hardie siding effectively while keeping its high quality intact.

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Can You Pressure Wash James Hardie Siding?

The manufacturer recommends that you do not pressure wash your Hardie siding. The hard spray of water from the power washer can damage the surface of the siding. In fact, pressure washing fiber cement siding is one of the only ways you can damage this durable type of siding.

Instead, use a soft cloth and soft bristle brush to clean your siding as needed. Wear safety goggles and gloves, gather your equipment and get started.

Cleaning Dirt Off James Hardie Siding

You can get the same sparkle as when you first installed your James Hardie siding by simply cleaning it once or twice per year. Use a soft brush, cloth and a garden hose to gently remove any dirt. Avoid employing anything abrasive, as this can leave marks on the fiber cement siding. Begin working at the top of a small section, so you can clean anything that drips or streams down.

Use your garden hose to wet your cloth or brush. When using a brush, use it to brush any dust or dirt off the siding, then rinse the area with your hose. When using a soft cloth, dampen the cloth, then wipe a small area from one side to the other in the direction of the plank, shingle or panel siding. Finally, rinse the area with your hose.

Cleaning Mildew and Mold From James Hardie Siding

Mildew and mold can sometimes accumulate after years of humid Virginia summers. Although it may look like dirt, it requires a different cleaning method. Use these steps:

  • Buy a mildew-removing cleaner. Make sure it specifically says to use it on mildew and mold. Read the instructions on the bottle before you begin.
  • Mix the cleaner with water. Try the solution on a small patch of the siding, following the mildew cleaner’s instructions, before you begin to make sure it doesn’t cause any damage. While most cleaners are safe to use on James Hardie siding, it’s always better to be cautious. After 24 hours, if the patch you tested looks good, you can go ahead and begin cleaning.
  • Spray the cleaner on the siding and use a soft cloth to lightly scrub the area, working from top to bottom on each section. Once you have finished a section, spray it with the garden hose to remove any remaining mildew or mold.

Removing Oil and Grease From James Hardie Siding

You can easily clean any grease and oil off your siding with a little elbow grease of your own. Use these steps:

  • Mix a mild dish detergent and water in a bucket until you have sudsy water.
  • Dip a soft cloth into the mixture and saturate it well. Rub the oil or grease off the siding. You may need to repeat this step more than once.
  • Rinse out your cloth in the bucket frequently to prevent grease and oil buildup.
  • Use a garden hose to rinse off the clean area. Do this continually, so the soap doesn’t dry on the siding.

Other Tips for Cleaning Your Fiber Cement Siding

Instead of using pressure washing that could damage your siding, keep these tips in mind for fast, effective cleaning:

  • If your siding is dusty from construction debris or chalk, no need to use soap — water is enough.
  • Rinse your rag frequently to clean off debris such as grease and prevent it from reattaching to your siding.
  • Make sure to rinse after using any cleaning solution such as mild dish detergent, so it doesn’t sit on your siding.

Rely on our best practices for cleaning your James Hardie siding as needed. Are you looking for new or replacement siding for your home? Get a free in-home consultation from Sunshine Contracting.

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