Best Plywood For Shed Floor – A Complete Guide

The best plywood for a shed floor is one that carries heavy loads and stands up to damp: exterior-grade or pressure-treated plywood suits most sheds, and marine plywood is worth considering where the floor will stay wet. For most small to medium sheds, 3/4-inch sheets fixed to level joists and sealed against moisture give a floor that lasts.

A shed floor has to support stored equipment, handle moisture and take regular foot traffic, so the material matters. Below are the plywood types that work best, what to check before you buy, the right thickness, and how to install and waterproof the floor.

Why Plywood Is Ideal For Shed Floors

Plywood is one of the most popular choices for shed floors, and for good reason:

• Strength and durability: Plywood is made by gluing multiple layers of wood veneer together. This layered construction makes it strong enough to carry heavy equipment, tools and foot traffic without sagging.
• Stability: Unlike solid wood, plywood is less likely to warp or crack under extreme conditions.
• Moisture resistance: Many plywood types are treated to resist moisture, which matters because sheds are often exposed to the elements. The treatment helps prevent warping, swelling and rot.
• Affordability: Plywood costs less than solid wood or most other flooring materials while still performing well.
• Easy to install and versatile: The sheets are large, relatively lightweight and easy to handle. They can be cut to any size to suit different shed designs and fastened securely to the base frame, which makes the job DIY-friendly.

Factors To Consider When Choosing Plywood For A Shed Floor

Before looking at the types of plywood, keep these points in mind:

1. Load capacity: The floor must support heavy items such as lawnmowers, tools and other equipment stored in the shed.
2. Moisture resistance: Sheds face changing weather, so a board that resists moisture is critical.
3. Thickness: Thicker plywood offers more support and stability, but it also costs more. See the thickness guide below.
4. Cost: Good-quality plywood costs more up front, but it is a sensible investment because it saves you from frequent repairs or replacement.
5. Plywood grade: Grades reflect the quality of the board and its intended use, so choose one made for outdoor or damp conditions, such as the types below.

Types Of Plywood For Shed Floor

There are several types of plywood, each with its own strengths. These are the best suited to shed flooring:

Exterior Grade Plywood

Exterior-grade plywood is designed to withstand outdoor conditions. It is bonded with waterproof glue that stops water getting in, so it resists rain and humidity and does not warp or crack easily over time. That makes it a strong choice for sheds where the floor may come into contact with water or damp.

• Advantages: High durability, water-resistant, ideal for sheds exposed to rain.
• Disadvantages: Slightly more expensive than untreated plywood.

Pressure-Treated Plywood

Pressure-treated plywood undergoes a chemical treatment that makes it resistant to moisture, rot, insects and fungi. It suits sheds placed directly on the ground or in humid surroundings, where the floor faces ground moisture or insect activity.

• Advantages: Resistant to rot, mould and pests.
• Disadvantages: The chemicals used in the treatment may raise some environmental concerns.

Marine Plywood

Marine plywood is one of the most water-resistant plywood options available. It is made with high-quality waterproof glue and durable wood veneers, which give it strong protection against moisture and rot. It is best suited to sheds in humid or wet climates, where the floor is constantly exposed to moisture.

CDX Plywood

CDX plywood is a popular budget choice for shed construction. The "C" and "D" grades refer to the quality of the outer layers, and the "X" indicates that it is meant for exterior use. It is not as polished as other types, but it is strong enough for most shed floors.

• Advantages: Affordable, strong and available in many thicknesses.
• Disadvantages: Rougher finish; may need extra sealing to protect it against moisture.

Choosing The Right Plywood Thickness

The right thickness depends on what the shed will be used for:

• 1/2-inch plywood: Only for small, lightweight sheds.
• 3/4-inch plywood: Ideal for most small to medium sheds, giving better strength.
• 1-inch or thicker plywood: For larger sheds and heavy-duty storage of equipment.

We recommend at least 3/4-inch plywood for a durable, well-supported shed floor. In that thickness, pressure-treated or CDX plywood offers a good balance of strength, moisture resistance and affordability.

Installation Tips For Plywood Shed Floors

Installing a plywood shed floor is straightforward if you follow these steps:

• Prepare the ground: Make sure the ground or foundation is level and stable before you start.
• Use joists: Lay joists across the foundation, spaced 16 inches apart, to support the plywood.
• Secure the plywood: Fix the sheets to the joists with galvanised screws, which hold better than nails and keep the floor in place even under heavy loads.
• Leave expansion gaps: Allow slight gaps between sheets so the boards do not warp.

Waterproofing Your Shed Floor

A waterproof floor prevents moisture damage and extends the life of the whole shed:

• Start with waterproof plywood: Exterior-grade, pressure-treated or marine plywood.
• Seal the edges, joints and surface: Apply a waterproof sealant so moisture cannot seep in.
• Install a vapour barrier: Lay it underneath the plywood.
• Keep water away: Elevate the shed floor so water cannot pool under it, and make sure there is proper drainage around the shed.

For more methods, see our guide to waterproofing plywood.

Budget Shed Flooring Ideas

If you are working to a tight budget, these options can help:

• OSB (oriented strand board): Made by compressing wood strands with adhesive, OSB is a budget-friendly alternative to plywood that gives good strength and support. It is not as water-resistant as plywood, though, and can swell and degrade if it stays damp for long. Properly sealed and maintained, it works for sheds used for light storage or placed in dry spots. Compare the two in plywood vs OSB for flooring.
• Recycled wood pallets: Cheap to source, but they need proper treatment first.
• Painted plywood: A coat of waterproof paint improves durability.
• Vinyl flooring: Affordable, waterproof and easy to clean.

Conclusion

The right plywood makes a shed floor functional, durable and long-lasting. Whether you choose exterior-grade, pressure-treated, marine or CDX plywood, picking a suitable thickness, installing it on level joists and sealing it against moisture will make a big difference to the life of your shed. MRS Woodcraft supplies durable, moisture-resistant plywood; browse our plywood range or request a quote for your shed.