choosing plywood thickness How to Choose the Right Plywood Thickness for Your Project

choosing plywood thickness

How to Choose the Right Plywood Thickness for Your Project

Choosing plywood thickness is critical for ensuring the stability and durability of your construction project. One of the most common mistakes people make when buying plywood is choosing the wrong thickness. Too thin and your structure flexes, sags, or fails. Too thick and you're wasting money and adding unnecessary weight. Getting it right the first time saves time, money, and frustration on site.

This guide walks you through the most common plywood thicknesses, what each one is best suited for, and how to choose confidently for your next build.

Common Plywood Thicknesses and Their Best Uses

3mm — 4mm (Ultra-Thin)

Ultra-thin plywood is lightweight and flexible, making it ideal for:

• Curved surfaces and bent forms
• Backing panels for cabinetry and picture frames
• Craft and hobby projects
• Decorative overlays and veneering substrates

6mm — 9mm (Thin Sheet)

A versatile lightweight option used for:

• Drawer bottoms and cabinet backs
• Wall panelling and lining boards
• Light-duty shelving with short spans
• Roof sarking in sheltered areas

12mm (Medium Weight)

One of the most popular all-round thicknesses:

• General-purpose shelving and storage
• Furniture carcasses and cabinet sides
• Flooring underlayment in light-traffic areas
• Stair risers and treads (in conjunction with thicker boards)

15mm — 18mm (Standard Structural)

The workhorse of most building projects:

• Structural flooring and subfloors
• Wall and roof sheathing
• Workbenches and heavy-duty shelving
• Formwork panels
• Furniture tops and benchtops

25mm — 30mm+ (Heavy Duty Structural)

For maximum strength and load-bearing performance:

• Industrial flooring in high-traffic or heavy-load areas
• Marine vessel floors, decks, and structural frames
• Structural panels in commercial construction
• Heavy-load platforms and work surfaces

Key Factors to Consider When Choosing Thickness

1. Span Length

The longer the unsupported span, the thicker the plywood needs to be to prevent flex and deflection. As a general rule, increase thickness as span length increases.

2. Load Requirements

Consider the weight the panel will need to bear — both static loads (furniture, equipment) and dynamic loads (foot traffic, vehicles). Heavy loads require thicker, higher-grade plywood.

3. Moisture Exposure

In wet or humid environments, always pair the right thickness with the right grade. For structural wet-area applications, marine plywood in 18mm or thicker is usually the recommended choice.

4. Weight Constraints

In marine or transport applications, weight matters. Choosing the minimum effective thickness — rather than automatically going thicker — can meaningfully reduce overall project weight.

5. Surface Finish Requirements

If the plywood face will be painted, stained, or left visible, factor in the face veneer quality as well as thickness. Higher-grade faces are available across most thickness ranges.

Quick Reference: Thickness by Application

Still Not Sure? Ask the Cheerjet Team

Choosing the right plywood isn't just about thickness — it's about matching the right grade, species, and bond type to your specific application. At Cheerjet Plywood, our team works with builders, tradies, and DIYers every day to help them find exactly the right product.

Browse our Heavy Duty & Structural Marine Plywood and Professional & General Purpose Marine Plywood ranges, or get in touch for personalised advice.