Subfloor Failing? Use This Plywood Thickness Chart Before You Install!

A bouncy or squeaky floor isn’t just annoying, it’s often caused by subfloor plywood that’s too thin or poorly installed. If you're building or renovating, choosing the right plywood thickness can save you thousands in future repairs.

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:

👉 Contact TT Plywood now for a free consultation & material quote: info@ttplywood.com

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!

❓ Frequently Asked Questions (FAQ)

Q1: What thickness of plywood is best for tile flooring?
A1:  For tile or stone flooring, the total subfloor thickness should be at least 1-1/8 inches. This is typically achieved by using 3/4" plywood combined with 1/2" cement board or an uncoupling membrane.
Tile is rigid and prone to cracking — so the subfloor must be extremely stiff with no noticeable flex.

Q2: Can I use 1/2" plywood for subfloors?
A2: Generally, no.
1/2" plywood is too thin for most subfloor applications and will flex or sag, especially if joist spacing is 16 inches or more. This can lead to squeaky floors and structural issues.
-> The minimum recommended is 5/8" plywood, but 3/4" is preferred for strength and long-term durability.

Q3: Is OSB okay for subflooring?
A3: Yes, OSB is allowed and widely used in subfloor systems especially in new construction.
However, compared to plywood:

• OSB tends to swell more when wet
• It’s heavier
• It doesn’t hold screws as well over time

If budget is tight and moisture isn't a concern, OSB is acceptable.
But for bathrooms, kitchens, or second floors, plywood is the better long-term investment.

🛠 Still not sure which material fits your flooring project best?
👉 Contact TT Plywood for expert advice and plywood recommendations tailored to your subfloor needs.

📞Hotline/WhatsApp/Line/Kakao: +84 32 694 2288
📧Email: info@ttplywood.com