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Can You Put Hardie Board Over Plywood? (Quick Answers)

Hardie board is a specialized type of siding that is made with cement fibers to produce a product that is both more long-lasting and more aesthetically pleasing. 

When sand, water, cellulose wood fibers, and cement are mixed together, a material is produced that is excellent for defending the exteriors of residential buildings.

The exterior siding made of fiber cement has a positive reputation in the industry because of its low maintenance requirements, long lifespan, and most notably, its attractive appearance.

On the other hand, you have plywood which is also an essential tool to fulfill your necessities. Plywood is a type of wood that is produced by laminating multiple layers of wood together. 

Now let’s dive into some of the fascinating information about these two products and see if you can use them together. 

Hardie board over plywood:

You can put a Hardie board over plywood. The installation of a Hardie board on top of the plywood is a relatively common practice. You can decide whether or not to set up plywood behind the Hardie board based on the variety of Hardie boards available. But, you can use them for better support.

Plywood is commonly used in the construction of shelves, desks, and even walls. It’s cheaper than most woods, but it can’t be used for structural purposes. Plywood, however, does not need plywood backing.

But there are many benefits to putting the Hardie board over plywood. It is a much more time-effective choice to use the existing siding on your house if that siding is in good enough condition to be used as the substrate. 

If you use the plywood or the existing siding as the substrate for the new Hardie board siding, you will be able to cut the amount of money you have to spend on it by a sizable amount. This will save you a lot of money. 

Because doing so will require the time-consuming and financially burdensome removal of the existing siding and, after that, the installation of a new substrate material in its place.

Additionally, it may have a higher level of resistance to the insects. It is able to take in the heat. It will provide you with a warranty that is good for a long time.

What are Hardie boards? Is it the same as a cement board?

Fiber cement siding from James Hardie is a market leader. James Hardie Building Products, one of earliest and most successful manufacturers of this product, produces Hardie Board.

Cement board siding, also known as fiber cement, and its most popular brand name is Hardie Board. Thus, a Hardie board is the same as a cement board

Fiber cement is manufactured to withstand the harshest environmental conditions, including submersion in water, high winds, hail, and salt air. Hardie Board is highly resistant to fire.

To begin, they combine water, wood pulp, and cement in a mixing container. This results in a material that is similar to sludge and can be shaped into any design or shape at all.

After the ingredients have been combined, they are poured into a pan and then pressed into sheets. After pressing the mixture, any remaining water is extracted. After being formed into sheets, the material is subsequently sawn into boards for use as home siding.

After being made into boards, they’re baked under high pressure, tested for strength, and then painted. Finished fiber cement looks like wood. It’s denser than wood, but more durable.

How to install Hardie board over plywood?

Hardie board is applied to the vertical surface framing over water-resistant drywall and is installed over plywood for floors, counter tops, and any other horizontal surface. Hardie board is also used for ceilings. 

A fundamental process is followed during the correct installation of Hardie board, which guarantees a secure and stable surface upon which to lay tile. 

Inspect the surface:

Before you begin installing the Hardie board, you should first inspect the subfloor or any other foundational material. Be certain that the tops of all of the nails and screws are even with the top of the work surface.

Prepare the mortar mix:

In the event that it is required, make sure to prepare a specific quantity of thin-set mortar mix in accordance with the instructions provided by the manufacturer. 

You are free to move on to Step 3 at this time if the assembly of the walls does not require the use of mortar.

Measure the surface:

Start by laying down the first piece of Hardie board. Take accurate measurements of the area where the Hardie board will be installed so that precise cuts can be made. 

In addition, when installing along a wall’s length, the sheet should be trimmed and, if necessary, fall directly on the stud’s vertical centerline.

Score the cut line:

To split the Hardie board, use a utility knife to score along the lines drawn in. Use a wallboard block or other steel straightedge with a blade that is aligned with the cut line, and then score the line firmly with a knife that has a carbide edge. 

Break the Hardie board along the scored line by applying pressure on one side and lifting up on another.

Spread mortar:

Using a tile trowel that has a notch in it, spread a surface of slim mortar over the level surface, whether this is necessary. Continue on to Step 6 for the installation of the wall.

Place the Hardie board:

Attach the part of Hardie board to the ground using backer-board screws after positioning it so that it is either resting on thin-set mortar or flush against the wall. 

The distance between each screw head should really be roughly 6-8 inches from across the piece and approximately 2 to 3 inches in from the edges.

Complete the set up:

To finish the installation of a Hardie board panel, you will need to repeat Steps 4 through 6 depending on the situation.

Apply tape:

In order to finish preparing the substrate, extend fiberglass tape to all of the seams that occur in which Hardie board frames come together. Apply the tape in an even layer across each seam.  Hardie board has now become prepared for the installation of tile.

Can you install Hardie board without sheathing?

Yes, you can install a Hardie board without sheathing. Most homeowners live in their homes for years before discovering the sheathing. It’s totally fine if you didn’t realize there was no sheathing underneath the siding until after you removed it. 

A sheathing panel or board can be made from a variety of materials. It is never too late to sheath a house, no matter how old it is. Hardie Panels do not offer the structural support provided by sheathing, which is commonly used to prevent walls from racking. 

Insulation and protection for the underlying structure are two of the many functions that sheathing fulfills in a building. The lack of sheathing does not constitute a defect in the structure.

There is no need for alarm if you don’t have sheathing. If you need a new covering, you can get one reconstructed. But sheathing is essential if you plan to use fiberglass in the walls. If the sheathing isn’t there before the foam is injected, the siding will bow. 

The siding will be damaged as a result. Sheathing is required here because the alternative is unacceptable.

Is Hardie board stronger than plywood?

Hardie board, also known as cement board, is, indeed, a more durable product than plywood. Cement board is typically utilized in areas that are external and therefore subjected to environmental exposures. 

In order to make Hardie board, Portland cement, surface sand, fiber, and a variety of other additives are mixed together during the manufacturing process. Following that step, the mixture is blended with fiber cement. 

This product is also known as cement-fiber siding, fiber cement cladding, and concrete siding. All of these names refer to the same thing. Cladding made of fiber cement is another name for this material.

Plywood is manufactured by laminating numerous thin sheets of wood, also called veneers. It can have at least seven plies (layers) and as many as twenty-one (or more).

After that, these layers are bonded to one another with a specialized concoction of cements and resins, and after that, they are molded into their final form by being pressed together. It is important to remember that plywood is typically crafted from softwood. 

Hardie board needs low maintenance, it has UV resistant coating, also it can reduce the amount of carbon that you leave behind. Because of all these, Hardie boards are better and stronger than Plywood. 

Final thoughts

Hardie boards can be installed over plywood. It is often installed over the plywood as a finishing touch. Based on the different types of Hardie boards available, you can choose whether or not to install plywood behind the board. However, they can be utilized to provide enhanced stability.