How to Clean Your Hardie Board

With hardie board, you’ve got a durable, great looking siding for your home. And while it can withstand all kinds of damage, washing it can be tricky. If you don’t know what you’re doing, you could end up damaging your siding! This guide will explain the best ways to clean your hardie board for maximum results as well as explain how to avoid damaging your hardie board siding.

What is Hardie Board Plank?

Hardie board siding is a fiber cement siding that is made to look like wood but without the maintenance. Hardie board planks are fireproof, termite proof, and weather resistant. It comes in a variety of colors and textures and can be cut and installed like wood. 

Hardie board siding is becoming increasingly popular because it does not rot, crack, or get warped like wood does. It is also low maintenance because it does not need to be repainted or sealed like wood does. Hardie board siding is a great option for those who want the look of wood but without the hassle of maintaining it.

Tips for Cleaning James Hardie Siding

Here are some tips to help you clean your hardie board siding.

Tip #1: Always pre wet before applying soap

The first thing you need to remember is to pre-wet the siding before you start cleaning. This is a crucial step because it will help prevent the soap from drying on the siding and causing streaks.

To pre-wet, simply use a garden hose with a pressure nozzle to wet down the entire area you’ll be cleaning. Start at the bottom and work your way up.

Tip #2: Never use high pressure always soft wash

The second tip is to never use high pressure when cleaning Hardie Board siding. High pressure can damage the siding. If you do want to use a pressure washer (and we wouldn’t recommend a novice use it), be sure to only use a low pressure setting on your pressure washer.

Tip #3: Test your soap mixture in a hard to see area to make sure it doesn’t harm the paint.

The third tip is to always test your soap mixture in a small, hidden area before applying it to the entire siding. This will ensure that the soap does not harm the paint or finish on your siding.

To test, mix up your soap according to the manufacturer’s instructions. Then, apply it to a small section of siding and pressure wash it off. If there is no damage to the siding, you’re good to go!

Tip # 4 Make sure to rinse thoroughly:

The fourth and final tip is to make sure you rinse the siding thoroughly after cleaning. This will remove any soap residue and prevent streaking.

If you’re ever confused about what cleaning method to use, you can always consult the official maintenance guide.


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Tools Needed to clean hardie board 

  • Bucket: You will need a bucket to mix the soap and water solution.
  • Mild Soap: Any mild soap will do. You can find this at your local grocery store.
  • Soft Bristle Brush: A soft bristle brush is necessary to apply the soap solution to the siding. Do not use a hard bristled brush as this can damage the siding.
  • Garden Hose: You will need a garden hose to wet down the siding before you start cleaning.
  • Soft cloth: A soft cloth is all you need to wipe down your siding on a weekly basis. This will remove any dirt, dust, or grime that has accumulated on the surface.
  • Pressure Washer: A pressure washer is a controversial choice because in the wrong hands it can damage the siding. However, in the right hands, it can speed up the job tremendously, just remember to only use a low pressure option.

Can you pressure wash hardie board? 

Hardie board siding is incredibly popular with just how durable it can be, but the one area where it is vulnerable is pressure washing. The high pressure of the water is able to erode away at the surface of the Hardie board siding in much the same way as the sea erodes away a cliff face.

Because of this, it isn’t recommended that you use a pressure washer yourself when cleaning your Hardie board siding and instead rely on tools like brushes or soft cloths to get the job done.

However, more experienced pressure washers or a professional service with experience of cleaning Hardie board sidings can use a pressure washer to good effect, as long as they use a low pressure setting.

How do you remove oxidation on hardie board? 

If you notice white, chalky substance appearing on your hardie board, it’s likely a sign of oxidation.

To remove oxidation, mix a solution of 5 cups of vinegar to one gallon of water. Apply the mixture to the affected area with a soft bristle brush. Let it sit for 15 minutes then rinse it off with a garden hose. Repeat if necessary. 

Cleaning mildew and mold from hardie siding

Cleaning mildew and mold from your Hardie siding is typically a very similar process to your typical clean. Use a combination of warm water and a James Hardie® approved mildew cleaner and then wash the areas with mildew and mold with a soft cloth and hose.

However, we like to go the extra mile with our cleaning service and so we use a light sodium hypochlorite mix and water with a surfactant soap to kill and mold and mildew. This has a much longer lasting effect and our clients have seen great long term results, but you need to be careful if you try doing it yourself as you don’t want to damage the siding.

Tips for hiring pressure washing services

Hopefully now, you have some clarity on the best practices for cleaning your hardie board siding. As long as you follow the tips we’ve laid out and avoid using high pressure washers, you can keep your hardie board siding clean and safe.

If you’re still confused or are worried about doing all this cleaning yourself, then why not get in touch for a free estimate today.

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