Can Hardie Board Be Used Outside? (Yes, But Avoid This!)


Hardie board has many benefits. It’s long-lasting, low-maintenance, and resistant to fire, moisture, pests, and insects.

But is it limited to indoor applications, or can Hardie board be used outside?

Hardie board can be used outside for most applications, but it can’t be used more than 30 feet above grade. It’s not suitable for use as a backer board in balcony parapet walls or balcony railings. While Hardie board is extremely water-resistant once installed, be careful to keep it from becoming saturated before installation as the moisture can damage it.

Read on to learn about the situations in which Hardie board is good for exterior use. We’ll also talk about whether it can get rained on, whether it needs to be waterproofed, if it’s as good as brick, and if it breaks easily. 

We’ll discuss the difference between Hardie board and cement board as well.

Is Hardie Board Good For Exterior Use?

You can use Hardie board for most exterior applications. According to the official installation guide, it can be used up to 30 feet above grade, or through the second story above grade if it does not exceed 30 feet.

Hardie board can’t be used as a backer board in balcony parapet walls or balcony railings. 

You have to install the Hardie board over sub-sheathing and with a water-resistive barrier if required by local building codes. It’s also necessary to install clearances and flashings according to your local code. 

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When installing Hardie board outdoors, you’ll need 8-gauge or 11-gauge nails that are 1¾ inches long. Another option is to use ribbed wafer head corrosion-resistant screws.

Your fasteners should be spaced a maximum of eight inches apart. The overlayment on top of the Hardie board, which includes stones, tiles, and veneers, has a weight limit of 15 pounds per square foot.

Can Hardie Board Get Rained On?

Hardie board is highly water-resistant, thanks to the concrete fibers it contains. This means it holds up well to weather conditions like rain, hail, and humidity. 

However, Hardie board should not get wet before installation. It’s recommended to store it in its original packaging in a covered area like a shed or garage so it’s protected from the weather. It’s also important to keep Hardie board off of the ground.

If Hardie board gets wet before it’s installed, there are a few issues that can result. 

The first is staining. If the Hardie board becomes saturated, you might notice that white salt deposits appear on its surface. 

Another potential issue if Hardie board gets wet before installation is shrinkage leading to open joints. Installing a wet Hardie board can lead to the joints between planks opening up and needing to be repaired or replaced altogether.

Finally, a wet Hardie board is much heavier and more flexible than a dry Hardie board, so it will be much more difficult to handle.

According to the general product information for Hardie board, it’s important to protect it using an additional waterproof covering if you’re storing it outside. 

If the Hardie board does become saturated before installation, you’ll need to lay it out on a flat surface and allow it time to fully dry before you install it.

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Does Hardie Board Need To Be Waterproofed?

It’s optional to waterproof a Hardie board unless your local building code requires it.

Building codes often vary from place to place, so be sure to look into the rules and regulations for your specific area to get a definitive answer regarding waterproofing.

Is Hardie Board As Good As Brick?

Hardie board and brick are comparable in many ways, but they do have their differences.

For example, brick tends to last longer and can stand up to the elements for over 100 years. It is also better than Hardie board when it comes to sound and thermal insulation. 

However, brick is harder and more labor-intensive to install than Hardie board, and Hardie board is less expensive than brick. It’s less expensive to repair Hardie board than brick as well.

Aesthetically, you’re more limited with brick than with Hardie board. Hardie board comes in a wide variety of colors and can also be painted pretty easily.

Meanwhile, brick usually only comes in reddish shades and darker earth tones and is more difficult to paint.

Does Hardie Board Break Easily?

Before installation, Hardie board tends to be a bit fragile and brittle. You have to be careful to store, carry, and install the planks properly.

You also have to use the right types of nails and guns so that you don’t nail too shallow or too deep.

It’s important to note that even though Hardie board comes with an excellent warranty, that warranty will be voided if you haven’t handled and installed the Hardie board correctly.

To avoid your Hardie board breaking, make sure to have two people carrying it at all times. It’s best to carry Hardie board vertically instead of horizontally; it can break under its own weight.

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The Difference Between Hardie Board And Cement Board

Hardie boards and cement boards are very similar and have many of the same benefits, but their main difference lies in some of the ingredients they’re made from.

Overall, though, Hardie board is a name-brand version of generic cement board.

Hardie board is a specific type of fiber cement siding composed of water, Portland cement, sand, cellulose fibers, and proprietary additives. It’s long-lasting, non-combustible, and made to withstand moisture, rot, and weather.

Cement board is a building material made of cement, water, limestone flour, silica, and fibers like fiberglass or Kevlar. It’s porous, making it easy for mortar, grout, and thin-set to adhere to it.

It’s also inexpensive, durable, and highly resistant to issues like mold, shrinkage, and rot.


Hardie board is suitable for most outdoor applications. However, there are some exceptions: You can’t use it as a backer board for balcony parapet walls or balcony railings, and you can’t use it more than 30 feet above grade.

When preparing for outdoor installation, be careful not to let the Hardie board get wet or saturated. It’s very water-resistant once installed, but if it gets wet before installation, this can cause problems like staining, increased weight and flexibility, and open joints.