Damage to siding arising from improper cleaning or maintenance may not be covered by the James Hardie warranty. Using wide fan tips that are kept a minimum of 6 feet from the wall and at pressures under 1500 psi will minimize the chance of damaging the siding.
If choosing to pressure wash your Hardie Board siding, you never want to go above 1500 psi — going any higher than 1500 psi risks ruining your Hardie Board siding.
Standing too close to Hardie Plank, even using a pressure level below 1,500 PSI, can still damage the material.
Typically, a pressure range of 1300 to 1600 PSI is sufficient for most types of residential siding, including vinyl, wood, and aluminum. Always refer to the manufacturer's recommendations for the specific material you are cleaning.
Don't: Pressure Washers
While using a garden hose to wash your fiber cement siding is acceptable, you should never use a high-pressure power washer to clean your siding.
Vinyl siding can withstand a powerful gas pressure washer (2,500-3,000 psi). Aluminum, stucco or soft-grain wood homes will do better with a less powerful washer (about 1,200-1,500 psi).
We'll be using a simple solution of a mild liquid dishwashing soap like Dawn®, Ivory® or Joy®. Just like you should never use an abrasive brush, never use any harsh chemicals to clean your siding. To clean your siding, wet your soft cloth with soapy water.
For most common outdoor surfaces like wood decks, vinyl siding, and concrete driveways, a pressure washer with a PSI range of 500-2000 should provide effective cleaning power without risk of damage when used properly.
What is the Ideal Water Pressure for My Home? It's important to maintain your home's water pressure within an acceptable range. The ideal water pressure ranges between 40 and 80 pounds per square inch, with the recommended home water pressure at 60 psi.
The yellow 15-degree nozzle is the best choice for siding and similar surfaces. When cleaning siding, you need to start at the top and work your way down. Keep the nozzle a consistent distance between 3 to 4 feet from the surface you are cleaning and keep the nozzle moving to avoid causing damage to the surface.
Instead, a low-pressure hose is all you need to keep your James Hardie siding clean. Simply rinse down your siding with the hose mix together a cleaning solution using water and mild liquid dishwashing soap. Then, gently wash away dirt and grime with a soft cloth or a long-handled, soft medium bristle brush.
Set the pressure washer to a low-pressure setting, generally between 1500 and 2000 PSI.
Top Cleaners for Hardie Board Siding
HardieClean – Specifically for Hardie board. Gently removes dirt and grime. Simple Green House and Siding Cleaner – Safe for nature; strong on grime. 30 Seconds Outdoor Cleaner – Great on stains and mold.
James Hardie Fiber Cement Siding Design
The “Exposure” or Reveal means how much of the lap siding is visible. The standard new construction siding and most economic option is a 7” reveal exposure (8 1/4” James Hardie Plank board with a 1 ¼” overlap per James Hardie Elite Contractor Preferred Guidelines).
Household bleach can be used to kill mold and mildew. Use a hand sprayer to apply household bleach to your fiber cement siding. Let the bleach sit a few minutes before rinsing it off with a hose. You may have to repeat this step a few times to completely remove the mildew or mold.
Siding guns or roofing nail guns can be used to fasten HardiePlank® lap siding, HardiePanel® vertical siding or HardieShingle® siding, provided they are adjusted to the appropriate settings and use the fasteners specified in the installation instructions.
Normal water pressure is generally between 40 and 60 PSI. Most homeowners prefer something right in the middle around 50 PSI. Once you measure the water pressure in your house, you can adjust it to a setting that is ideal for all family members and household uses.
Maintaining water pressure between 40–60 psi is recommended for well water systems. It's important to periodically test the water pressure to ensure it falls within this range and detect any issues early on.
But you shouldn't go too much over recommended PSI. You can safely over-inflate tires by up to 10%. For example, if your tires have a recommended PSI of 35, you can go up to around 38 PSI without worry. Anything more than that is too much and not recommended.
For example, a 2,000 square foot home can take anywhere from one to three hours to power wash.
Final Verdict. The Ryobi 1900 PSI Corded Electric Pressure Washer is our pick for the best pressure washer. After testing, we found it highly effective at cleaning typical surfaces around a home's exterior, including walkways, decks, fences, patio furniture, and cars.
In general, siding and driveways are the most common surfaces that can be easily cleaned with a pressure washer rated at 2,000 PSI, with a tip capable of delivering 2,000 pounds of force per square inch. For most people, this will be a good choice as it can handle most tasks around the house without breaking the bank.
Most homes should be power washed a minimum of once a year. Power Washing your siding will actually extend the life of it so it won't need repairs and you won't need to replace it as often. It also makes your home look as good as new when it's tidy and clean on the exterior.
Flat paint finishes will give your siding a soft, velvety finish and is the easiest option to apply to your home's exterior, since flat finish provides thorough coverage.
What is the best way to keep Hardie Board looking its best? Depending on the type of mess that needs to be cleaned, there are various techniques and tools, such as: Using a pressure washer to clean algae off of the siding. Using a mixture of vinegar, hydrogen peroxide, and dish soap to clean the algae.