What Thickness Ply for Flooring? Complete Guide

Choosing the wrong ply thickness for your flooring project can lead to squeaks, bounce, and costly repairs down the line. Understanding what thickness ply for flooring works best in different situations will save you time, money, and frustration. Whether you’re laying laminate, engineered wood, or tiles, getting the subfloor thickness right is crucial for a professional finish that lasts.

Why Does Ply Thickness Matter for Your Flooring Project?

The thickness of your plywood subfloor directly affects the structural integrity and performance of your entire flooring system. When you install flooring over inadequate plywood thickness, you create a recipe for problems that will haunt you for years. Insufficient ply thickness leads to floor deflection, which causes that annoying bounce underfoot and creates gaps in laminate joints. Your beautiful hardwood floor might develop squeaks that drive you mad during quiet evenings. Even worse, tiles can crack when the subfloor flexes too much beneath them. The right plywood thickness distributes weight evenly across the joist system, preventing these issues whilst providing a solid foundation that keeps your flooring looking and performing at its best for decades.

Which Ply Thickness Works Best for Standard Joist Spacing?

For standard residential construction with 16-inch joist spacing, minimum 5/8-inch (16mm) plywood provides adequate support for most flooring applications. This thickness meets building regulations whilst offering good value for money. However, many professional installers recommend upgrading to 3/4-inch plywood even with 16-inch spacing, particularly if you want extra peace of mind. The additional thickness costs relatively little compared to your total project budget but delivers noticeable improvements in floor stability. You’ll feel the difference when walking across the floor – that solid, non-bouncy feel that screams quality craftsmanship. Remember that existing homes built decades ago might have different joist spacing, so always measure your actual spacing before selecting plywood thickness.

Should You Choose 3/4-Inch Ply for Wider Joist Spacing?

When dealing with 19.2-inch or 24-inch joist spacing, 3/4-inch (19mm) plywood becomes non-negotiable for maintaining structural performance. The wider spans between joists create much greater stress on the plywood, and thinner materials simply cannot handle the load without excessive deflection. Many builders use wider joist spacing to save on timber costs, but this places greater demands on the subfloor material. Using inadequate thickness over wide spans creates a trampoline effect that will telegraph through any flooring material you install on top. The extra cost of 3/4-inch plywood pales in comparison to the expense of ripping up a failed floor installation later. Professional tilers and flooring contractors won’t guarantee their work over inadequate subflooring, so getting this right protects your investment.

What Ply Thickness Do Hardwood and Laminate Floors Require?

• 3/4-inch (19mm) minimum thickness provides the stability these flooring types demand
• Hardwood flooring expands and contracts with humidity changes, requiring a rock-solid base
• Laminate floors with click-lock systems need stable support to prevent joint separation
• Thinner plywood allows too much movement, voiding manufacturer warranties
• Professional installers refuse to work over substandard subflooring

Both hardwood and laminate manufacturers specify minimum subfloor requirements in their installation guidelines, and using thinner plywood typically voids your warranty coverage. The precision-engineered joints in modern laminate systems work brilliantly over proper subflooring but fail quickly when the subfloor moves excessively.

How Thick Should Ply Be Under Tile Flooring?

Tile installations require the most robust subflooring system because ceramic and stone materials have zero tolerance for movement. You need 1-1/4 inch total thickness, typically achieved by combining 3/4-inch plywood with cement board on top. This layered approach provides the ultimate in stability whilst creating the perfect surface for tile adhesive bonding. The plywood layer handles structural support, whilst the cement board provides the alkaline-resistant surface that tile systems require. Some installers try to cut corners by using thinner plywood under cement board, but this creates a weak point in the system. When tiles start cracking or popping loose, the repair costs far exceed the money saved on thinner materials. Professional tilers know that proper subflooring is the foundation of every successful tile installation.

Can Thinner Ply Work for Carpet Installation?

Carpet represents the most forgiving flooring option when it comes to subfloor thickness requirements. 5/8-inch to 3/4-inch plywood provides sufficient support for carpet installations because the carpet padding absorbs minor imperfections and movement. The thick padding layer acts as a buffer between your feet and the subfloor, masking small amounts of deflection that would be unacceptable under hard flooring materials. However, don’t assume that carpet excuses poor subflooring practices. Excessive movement still causes premature carpet wear and can lead to squeaking from loose subfloor panels. Even with carpet’s forgiving nature, using proper plywood thickness creates a better foundation that will serve you well if you decide to change flooring types in the future.

What Do Building Codes Say About Ply Thickness?

• Building regulations vary by local authority across the UK
• Most councils reference British Standards for minimum thickness requirements
• Some areas have specific rules for flood-prone regions or high-traffic applications
• Always check with your local building control office before starting work
• Planning permission applications must show compliance with current codes
• Building control inspectors will check subfloor thickness during construction

Your local building control officer provides the final word on what’s acceptable in your area, and their requirements take precedence over general guidelines. Some councils have updated their standards following changes in construction practices or materials technology.

Which Ply Thickness Should You Choose for Your Project?

The right plywood thickness depends on your specific combination of joist spacing, flooring type, and local building requirements. For most homeowners, 3/4-inch plywood provides the best balance of performance and cost across different applications. This thickness works with standard 16-inch joist spacing, handles wider spans adequately, and provides excellent support for any flooring material you might install now or in the future. When budgeting your project, remember that subfloor materials represent a small percentage of total costs but have enormous impact on the final result. Spending an extra few pounds per sheet on proper thickness prevents expensive problems and ensures your beautiful new flooring performs exactly as intended. Your future self will thank you for making the right choice today.

 

FAQ

What is the most common plywood used for flooring?

CDX. CDX plywood is the most common plywood used for subflooring. It is usually more affordable because it is rougher and has more imperfections than other types of plywood. However, since subflooring is almost always covered and rarely visible, the way it looks should not matter.

Should you leave a gap between plywood flooring?

APA recommends a 1/8-inch space between panel edge and end joints. Plywood and oriented strand board (OSB), like all wood products, will expand or shrink slightly with changes in moisture content. If the wood structural panels are tightly butted, there is no room for expansion and buckling can occur.

Is 1 2 inch plywood strong enough for flooring?

Yes, 1/2 inch plywood is often used for subflooring in residential construction. It provides a good balance between strength and weight, making it suitable for this application. However, it should be used with proper underlayment and support to ensure stability and durability.

 

Sources

[1] https://www.fromtheforest.com/blogs/fromtheforest/how-thick-does-a-plywood-floor-have-to-be [2] https://community.screwfix.com/threads/plywood-thickness-recommendation-for-flooring.242799/ [3] https://eastcoastfl.com/blog/types-of-subfloor/