How To Remove Oxidation From Hardie Board Siding

Removing oxidation from Hardie board siding can be intimidating if you’ve never done it before, but with some practice and guidance, anyone can become a pro!

Oxidation is a natural process that happens over time as elements in the environment like sun, wind, and pollution cause damage to your home’s exterior.

By understanding what oxidation is and how to tackle you can restore your Hardie board siding or other material to its original finish.

Whether you’re an experienced professional or just starting out in the world of home maintenance projects, this guide will give you vital tips about how best to remove oxidation from Hardie board siding.

So before we get into the detail, let’s start with the takeaway.

Hardie board siding is a durable material but can be affected by oxidation, it can cause fading, chalking, spotting, and wear and tear, ruining the appearance of the siding. Removing it requires care and patience but can restore the siding to its original look. Ox-Knox solution mixed with water can be applied to remove it


Ok so with the brief covered, let’s start by finding out more about the oxidation process so you can more easily understand how to remove it from your hardie siding.


What is oxidation on Hardie board siding?

If you are a proud owner of Hardie board siding, you already know how beautiful and durable it is.

But have you noticed that your siding has started to change color or become dull over time?

This type of board is a popular option due to its strength and durability, making it perfect for withstanding harsh weather conditions.

However, like all building materials, it can be affected by a process known as oxidation.

This process can affect the appearance and function of siding and can lead to discoloration and ruin its good looks!   

Oxidation is a natural chemical process that occurs when certain substances come into contact with oxygen over time.

It is a slow, gradual reaction that can cause rust and decay.

However, it can also affect materials like Hardie board siding, which is made of a blend of cement and cellulose fibers.

When exposed to oxygen, the cellulose fibers in the siding can break down and lose their color, resulting in a faded or dull appearance.

So how does this process ruin your curb appeal?

Let’s find out.

How Oxidation Affects Hardie board siding

This process can have a severe impact on the overall appearance of Hardie board siding.

The major impact can be seen with regard to fading and peeling of paint as the surface of the siding breaks down due to prolonged exposure to moisture and harsh weather conditions.

It can affect your Hardie board siding in several ways, including:

  • Fading: As we mentioned earlier, oxidation can cause your siding to lose its color and look dull or faded.
  • Chalking: Oxidation can also cause a powdery substance called “chalk” to form on the surface of your siding. This can be unsightly and difficult to remove.
  • Wear and Tear: Over time, a damaged siding can become weaker and more prone to damage. This can lead to cracks, chips, and other signs of wear and tear.

So what can you do about this wear and tear on your home?

How to remove oxidation from Hardie board siding

Our experts here at Southeast Softwash tackled a little restoration project on some seriously oxidized Hardie board siding recently.

A  hailstorm had left lots of oxidation in the form of spots on the surface. First things first, we could  easily tell that it was pretty severe.

No need for a detailed check when it was so obvious you could spot it from the road, it was that bad!

However, the paint underneath looked like it was still in decent shape.

So it’s worth understanding that if the paint is still in good condition underneath, we can restore it, make it look great, and give it several more years of life.

If the paint has failed and is oxidized, we’ll need to remove it before repainting.

Now, we know a lot of you painters out there are scrubbing, and working hard to get the job done!  but we’re here to make things easier for you!  Whether it’s restoring or repainting, we’ve got you covered.

We played around a little with the ratios to find the best approach.

Our main goal was to achieve a brushless situation. We know that brushing down a whole house can be not only tedious but heavy on your time! 

So here’s what we did.

We used some Ox-Knox to restore it, with a mixture of about four parts water to one part solution.

We generally use a pump-up sprayer or you could use an X-Jet pt’ll work just as well. But if rolling is your thing, go for it!

Before we started applying the solution, we pre-wet the wall, working on a small section at a time.

So we applied our Ox-Knox solution, let it sit for about five minutes, and rinsed it off with the ball valve. Pretty easy!

So how can homeowners prevent this from happening in the future?

Preventing Oxidation on Hardie board siding

Although Hardie board siding is known for its durability and strength, oxidation can be prevented or at least reduced by following some simple steps.

Regular maintenance can help extend the lifespan of your siding and keep it looking its best for many years!

This includes power washing once to twice a year, repainting when necessary, and cleaning the gutters to ensure there is no standing water that may eat away the paint.

How To Remove Oxidation From Hardie board siding – To end

Now that you have all the tips, you are well on your way to getting those grime spots gone.

Taking the time to remove oxidation not only brings back its original look but also helps preserve the material’s quality over time.

It’s important to note that though this is a DIY job, it requires care and patience in order to get the desired results. If done correctly, your Hardie board siding will be as good as new in no time!

Finally, don’t forget to tune into our regular blog posts whether you are a seasoned pro or a DIY homeowner for all things exterior washing.

For those of you who love to see a little ‘ hands on’ head over to our YouTube channel.


"Ox Knox is the bomb spray on and rinse off wow test spot prolly sign sealed and delivered this deal just trying to figure on pricing for this service since I’m the only one that can do it lol"
Premier Pressure Wash
Ox Knox Contractor