do you need plywood behind hardie board
Kristina Davis

Do you need plywood behind Hardie board? Suppose you own a small cabin on a wooded property and want to use Hardie board siding for fire resistance and longevity.

But can you do it without installing any plywood behind the siding?

It can be confusing because some experts say installing the board directly onto the studs over black paper is possible.

But others say it is vital to sheath the walls and use plywood before siding. So, does Hardie board need plywood backing?

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Adding plywood behind the Hardie board certainly offers some benefits, but you can also attach it directly to the studs without plywood backing. 

The Beauty of Going With Hardie Board Siding

hardie board siding

James Hardie siding is an attractive exterior option that can keep looking good for more than 30 years, even in extreme climates.

Your siding contractor must adhere to the manufacturer’s installation guidelines. If they do not, your siding will not last as long as expected. 

What Makes James Hardie Board Siding an Attractive Option?

The benefits of using Hardie siding are many. 

For instance:

  • It handles elements well and offers outstanding durability.
  • It offers an eye-catching curb appeal.
  • It works great to resist pests.
  • It comes with a 30-year non-prorated warranty.
  • It is not combustible and never contributes to a fire.
  • It is low-maintenance and extremely environmentally friendly.
siding board attractive option

Because of all these benefits, many people opt for James Hardie board siding to protect their exterior.

But, when it comes to installation, they have to answer a few questions, including whether or not plywood is needed before installation. 

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Do You Need Plywood Behind Hardie Board or Not?

do need plywood

Among the many fiber cement siding options is Hardie Plank. The material is long-lasting and requires little care, although it can be pricey.

Installation of Hardie Plank often raises the question of whether or not plywood backing is necessary. Usually, you do not have to go with this additional expense.

The truth is that Hardie Plank can be laid on top of existing subflooring or sheathing without additional preparation.

But ultimately, it all depends on what you truly want to achieve by switching to Hardie board siding. 

Going With or Doing Without Plywood Behind Hardie Board?

going without plywood

It is possible to install your Hardie board directly on studs without first sheathing the walls.

But remember that this method requires the application of let-in bracing to ensure the walls remain solid and stable.

A barrier, such as Tyvek or tarpaper, should be used underneath it.

However, it is worth mentioning that using plywood backing may not offer extensive structural help, but it has its advantages. 

If you use plywood behind your Hardie board siding, you may experience the following benefits:

  • It will be a lot quieter with plywood.
  • It will be more energy efficient and keep your property warmer.
  • It helps keep pests from entering your property.
  • It makes your property stronger against break-ins and vandalism.
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What Can Go Behind Hardie Board Siding?

back of hardie board

When you believe something should be behind your siding, it does not always have to be plywood.

👍 You certainly have other options to consider.

You can use plywood (of course), furring strips, or even metal lath as backing for the Hardie board.

Whatever you decide to install underneath the Hardie board must be reliably fastened to stay intact over time.

Tip: No matter your choice, ensure a tighter fit between the substrate and the Hardie board to prevent water damage.

Plywood Behind Hardie Board and Your Construction Project

plywood behind hardie board

Whether you should stick with plywood backing or do without it often depends on the material you use and the installation techniques. 

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Here are some factors affecting which way you should go: 

Check the Work Surface

Sometimes, the work surface is not level. Plywood may be needed to create a flat surface for the Hardie siding in certain circumstances.

Of course, it is possible to put it just over the existing surface, but it is not always the case.

Talking to a professional contractor is a must if you need help figuring out what steps to take with your construction project. 

Consider Where You Live

considered the place

Do you live in high-wind areas? Well, it will definitely affect your installation technique and material choices.

In high-wind areas, installing plywood below the Hardie Plank may be necessary to prevent it from peeling up.

Similarly, you may want to use plywood backing if you want to install your Hardie siding on an existing wood siding.

Using plywood will add more durability and strength to your siding, and it is less likely to split even when exposed to strong winds. 

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Consider Your Goal

consider the goal

What you want to achieve by using Hardie board siding also plays a role in deciding whether or not plywood backing is beneficial.

Using wood sheathing may not be a good idea if you only want to reduce your home’s energy consumption.

👍 A number of 0.63 R is all you can expect.

To put it another way, this is about as useful as adding another layer of drywall, and it is surely not worth the extra money.

putting another layer

On the other hand, going with wood sheathing makes a lot more sense if your goal is to increase the integrity of your property.

Older, historic homes benefit greatly from the added structural support that wood sheathing provides.

For sheathing, in particular, OSB is often the material of choice because it is stronger than plywood and surprisingly cheaper too.

Tip: Be sure to maintain a close fit during installation, with the boards contacting one another to improve the durability of your siding.

Pay Attention to Building Codes

attention to building

Whether you need plywood backing or you should choose a different material often depends on prevailing building codes in your area.

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In so many cases, installing siding over a water-resistant barrier and nailing it into studs is mandatory, according to construction codes.

In this situation, a better option would be to install your fiber cement siding directly over OSB, plywood, or skeet.

directly to osb

But, if you want to use backing mainly to prevent water damage, you must choose your material wisely.

Not all sheathing materials offer air penetration, water, and tear resistance.

You should not use Tyvek on the inside since it will not keep the moisture out, but it is great for the outside.

Furthermore, you may get good results using 4×8 foam items, provided they are rigid.

Can There Be Issues Other Than Plywood Behind Hardie Board?

plywood behind hardie board

Okay, so now you have gathered when you truly need to go with a plywood backing and when you can do without it.

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But, unfortunately, it is not the only confusing issue associated with Hardie board siding.

Many people make other mistakes that directly affect the performance of their siding. 

For instance: 

Touch-Up Mistakes

mistakes by installing

So often, you will find that many Hardie board installers end up botching the finishing touches.

The siding is painted and cured in factories; thus, the company’s touch-ups do not have the same shine.

As a result, you need to be cautious when painting over flaws such as nails or tiny cracks in your siding and its trim.

Tip: Do not use too much paint because the touch-ups will likely fade faster than the original paint on your board, making it look ugly.

Not Using Enough Fasteners

not enough using fastener

Due to its contemporary look and low cost, Hardie Panel with Easy Trim is popular among architects and builders. But it does not always work.

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It is mainly because you have to install the panels while fastening properly to the studs and maintaining a consistent pattern with nails and screws.

You have to realize that Hardie boards are not very thick, so they must be carefully fastened. If you do not, they can bend slightly under the pressure of the wind. 

You also need to get familiar with the various nail and screw patterns authorized for use with Hardie panels.

Tip: It is essential to avoid the issue of high nailing, or you might notice the nails poking through the next board and directly affecting the durability of Hardie boards.


Do you need plywood behind Hardie board siding? Well, you do not, at least in most cases.

But ultimately, it depends on your goals and the materials you use during installation.

The durability of your siding may also be affected based on the plywood backing, so be sure to consider your unique circumstances before you make a choice.