Plywood Thickness for Subfloor: The Ultimate Guide to a Solid Foundation

A sturdy subfloor is the unsung hero of any flooring system. Whether you're installing hardwood, tile, or luxury vinyl plank, the right plywood thickness for your subfloor ensures stability, prevents squeaks, and extends the life of your floors. But with varying standards and conflicting advice, how do you choose the best option?

In this guide, we’ll cover:

• Why plywood thickness matters for subfloors
• Recommended thickness based on joist spacing
• Plywood vs. OSB – which is better?
• Installation best practices for a long-lasting subfloor
• Common mistakes to avoid

Why Plywood Thickness Is Critical for Subfloors

The subfloor is the structural layer between your floor joists and finished flooring. Too thin, and it will flex or sag; too thick, and you waste money without added benefits. Here’s why getting the plywood thickness right matters:

1. Prevents Floor Flexing and Bounce

• Thin plywood (e.g., 1/2") over 16" joists will feel bouncy underfoot.
• Proper thickness (e.g., 5/8" or 3/4") ensures rigidity.

2. Supports Heavy Flooring Materials

• Tile and stone require a thicker, stiffer subfloor (minimum 3/4" plywood).
• Engineered wood or laminate can use thinner sheets (5/8").

3. Reduces Squeaks and Gaps Over Time

• Thicker plywood resists warping and movement.
• Proper fastening (screws > nails) minimizes noise.

Recommended Plywood Thickness for Subfloors

The ideal plywood thickness depends on joist spacing (the distance between floor supports). Here’s a breakdown:

1. Standard 16" Joist Spacing

• Minimum: 19/32" or 5/8" plywood
• Best Choice: 23/32" or 3/4" for extra durability

Why?

• 5/8" meets most building codes but may feel slightly flexible.
• 3/4" provides better stiffness, especially for heavy traffic areas.

2. Wider Joist Spacing (19.2" or 24")

• Required: 3/4" plywood (or thicker with additional underlayment)
• Alternative: Double-layer subfloor (1/2" + 5/8") for added strength

Note: Always check local building codes—some regions require 3/4" plywood regardless of spacing.

3. For Tile or Stone Flooring

• Minimum: 1-1/8" total subfloor (e.g., 3/4" plywood + 1/2" cement board)
• Why? Tile is rigid and needs zero flex to prevent cracking.

Plywood vs. OSB for Subfloors: Which Is Better?

Two main materials dominate subfloors: plywood and OSB (oriented strand board). Here’s how they compare:

• Verdict:

How to Install Plywood Subfloor: Best Practices 

Even the best plywood fails if installed incorrectly. Follow these pro tips:

1. Choose the Right Plywood Grade

• Exterior or CDX plywood (glue holds up to moisture).
• Avoid interior-grade—it’s not strong enough.

2. Leave Expansion Gaps

• 1/8" gap between sheets (prevents buckling).
• 1/2" gap at walls (allows for seasonal movement).

3. Secure Properly

• Deck screws (or ring-shank nails) every 6–8" along joists.
• Avoid underdriving or overdriving (flush is ideal).

4. Stagger Seams for Strength

• Offset joints like brickwork (no four-way overlaps).

Common Subfloor Mistakes to Avoid

 Using Thinner Plywood Than Recommended

• Example: 1/2" plywood over 24" joists = sagging floors.

 Skipping Underlayment for Tile

• Tile needs cement board or uncoupling membrane over plywood.

 Ignoring Moisture Protection

• In basements, use pressure-treated plywood or a vapor barrier.

Final Thoughts: Build a Subfloor That Lasts

Choosing the correct plywood thickness for your subfloor isn’t just about meeting code—it’s about ensuring a solid, silent, and stable foundation for years to come. Remember:

• 16" joists? Use at least 5/8" plywood (3/4" for best results).
• Wider joists? Upgrade to 3/4" or double-layer.
• Tile floors? Reinforce with additional underlayment.

When in doubt, consult a contractor or local building inspector. A little extra effort now saves costly repairs later!