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What Type of Plywood is Good for a Subfloor?

A collage of plywood for subflooring.

Standard plywood is great for subflooring because it is cheap and reliable. A ¾-inch tongue-and-groove plywood subflooring is perhaps the best overall material to use because the edges interlock, which allow the panels to resist movement.

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There are many reasons a strong subflooring is important for your home. If you use the wrong materials for your subflooring, your tiles may crack, gaps can open up, or you can have a squeaky floor. 

Subflooring is the part of the house you don’t see but happens to be one of the most important aspects. While choosing the right tile or wooden floor is important, it can always be replaced at a later date. Your subfloor is considered permanent and is attached to your home’s framing.

To help you pick the best plywood for your subflooring, we will go over the best types to use for your home.

Related: The History of Plywood | What Type of Plywood is Good for Cabinets?

What Type of Plywood Is Good for the Subfloor?

Different type of tiles and plywood piled up.

Two main types of plywood are ideal for sub-flooring: CDX and Tongue and Groove. However, if you’re doing a DIY project, it’s important to know about and understand what subflooring is.

Wooden, structural subfloors are used to support the installation of durable flooring. Today, plywood is the most used subfloor material. Plywood comes in a wide variety of shapes, sizes, and layouts. 

Depending on the intended function, different types of plywood are made with a variety of materials and processes. Plywood subfloors come in a variety of varieties.

The Thickness of Plywood Subfloors

As a general rule, a plywood subfloor is made out of sheets of plywood that are between ¾-inch and ½-inch thick, each with a rough and a smooth side. Four-by-eight or four-by-twelve foot sheets are the most common.

Gluing and pressing several thin slices of solid wood together at 90-degree angles results in a remarkably strong structural sheet, which is what is known as plywood. Solid wood planking was swiftly supplanted as a subfloor material in homes by this product in the 1950s.

Subfloors can be made of standard plywood, but tongue-and-and-groove sheets that interlock at the edges are more frequent. The optimum plywood subfloor thickness is determined by the joist spacing.

For joist spacing of 16 inches or less, some experts recommend using 15/32-inch plywood; for joist spacing of more than 16 inches, ¾-inch plywood must be used. Consult your local code authority, however, for the most up-to-date information.

What Determines Subfloor Thickness?

The thickness of plywood required for subflooring is approximately ⅝-inch thick. ‘ OSB must be a minimum of 23/32 inches thick because it does not retain nails as well as plywood.

The thickness of the subfloor is determined by several elements, including the amount of insulation it provides. All of these aspects must be taken into consideration because each one can restrict the thickness of the subfloor.

Dimensions of the Joists

Floor joists made from plywood and OSB.

The distance between the floor joists, on which the subfloor rests, is a critical determinant of subfloor thickness. The larger the distance between the joists, the greater the thickness of the subfloor necessary for structural purposes.

When joists are less than 16 inches apart, a half-inch of subflooring may suffice. You’ll need a thicker subfloor for stability in older homes with more dispersed joists. For this project, 7/8-inch plywood and 1-inch OSB are a must.

The feel of your floor can be greatly influenced by the stiffness of the subflooring. Additionally, it performs a significant role in making sure that your floor remains flat and even. As a result, you must choose the correct subflooring thickness for your home’s construction.

Why is this relevant? So, while denser subflooring might have better insulation, it could reduce the counter space for underlayment options. 

Vertical Spacing

The “R-value” of a product’s insulating capacity should be taken into account when determining the proper thickness of flooring material. 

Higher R-value building materials are better at keeping the heat in during winter and keeping it out through the summer, respectively. R-values range from one of the greatest — for wool carpeting — to one of the lowest — for thin, engineered wood.

Subflooring is the same. OSB has a higher R-value per inch (2.0) than plywood (1.1). (1.4 per inch). As a result, while structurally thinner plywood may be acceptable, its insulating qualities will be inferior to that of OSB of the same depth.

This is a critical factor to keep in mind, especially if there is a little gap between your floor and the slab or crawlspace. As a general rule, if you’re dealing with a narrower vertical space, you’ll want to use a product with a greater R-value.

Subflooring Plywood Options


CDX plywood is the most often used subflooring plywood. The roughness of the outer layer is graded from C to X. Due to its location in an area of the house that is rarely seen, a higher grade of flooring isn’t necessary.

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Imperfections and roughness are common characteristics of CDX plywood. As a result, buying by the sheet is substantially more affordable. It’s a popular choice for homeowners because it’s inexpensive and robust.

Plywood letter grades are based on appearance only, not on overall quality. The strength of CDX plywood is on par with that of higher grades. It can be used for exterior sheathing in the same way as OSB. However, it is less water-resistant.

Tongue and Groove

A man attaching two wooden plank using a wood glue.

T and G is a form of woodworking joint known as “tongue and groove” or “T and G.” It’s like a mortise and tenon in appearance. 

The plywood has a protruding ridge that slides into a groove in the adjacent edge. OSB (a plywood substitute) and CDX subfloors are available in tongue and groove form.

It’s perfect for subflooring since it stops the plywood’s edges from shifting and squeaking after the insulation has been installed. Tongue-and-groove joints can be sealed more effectively with construction glue. 

Main Alternative to Plywood

Subflooring Oriented Strand Board (OSB), or OSB, is among the most commonly used alternatives to plywood.

Wooden and structural subfloors are used to support the installation of durable flooring. Today, plywood is the most used subfloor material. Plywood comes in a wide variety of shapes, sizes, and layouts.

Based on the target function, different types of plywood are made with a variety of materials and processes. Plywood subfloors come in a variety of varieties.

Methods for Installing a Plywood Subfloor

A man installing a wooden plank on the floor.

Installing engineered or solid wood on a plywood subfloor with concealed nailing is the most common and preferred method. Nailing down either type of floor typically requires a thickness of at least 18mm, and staples or cleats are normally recommended for anything less than 18mm. 

A minimum of 50mm in length is required for nails or staples used to fasten wood flooring to the subfloor. Flooring planks can be nailed down directly on top of the plywood with this length. Check for service pipes before stapling or nailing anything down.

Next, you’ll need to apply glue to your floor. A floor adhesive can be used to attach both regular and engineered wood to a plywood subfloor. Wood glue and floor adhesive are two distinct things that should not be mixed.

Finally, there’s floatation. Floating engineered wood flooring is the most straightforward method of installation. It is necessary to glue the tongue and groove connections of the floorboards together after they have been lightly laid over the underlay.

When Is Multilayer Subflooring Needed? 

A man installing a subfloor using a hammer.

Subfloors are typically 5/8-inch thick or more in new construction. Another frequent thickness is 7/8 inch, and several subfloors are much more substantial. In new construction, multilayer subfloors are not used, although they are used in retrofits.

Using construction adhesive to attach CDX plywood to the previous floor and then nailing it down will remove much of the spring and creaks from a home with thinner joists with bouncy flooring, often known as floor deflection. When installing another layer of plywood on top of the original plywood or solid wood floor, it’s best to go with a thinner layer.