When building a shed, the floor is one of the most important elements to get right. It carries the weight of everything stored inside and is the first line of defense against ground moisture. Choosing the right materials and design can make the difference between a sturdy shed that lasts decades and one that begins to rot after just a few years.
Best Materials for Shed Floors
The most common choice is pressure-treated lumber for the floor joists and framing, paired with exterior-grade or pressure-treated plywood on top. These materials are designed to resist decay and hold up to the inevitable exposure to moisture. If you prefer extra durability, you can also consider composite decking boards or concrete slabs, but these options can be more costly and labor-intensive.
The Role of a Vapor Barrier
Many DIY builders consider laying a vapor barrier, such as heavy plastic sheeting, between the joists and plywood to stop moisture from creeping upward. While this can help, it’s not a complete solution. If water collects under the shed, a simple vapor barrier may trap moisture against the wood instead of keeping it out, speeding up rot.
Better Protection Strategies
To really protect your shed floor from moisture:
-
Elevate the shed – Set it on concrete blocks, gravel pads, or a slab to allow air circulation underneath and prevent standing water.
-
Use treated materials – Pressure-treated lumber and exterior-grade plywood last much longer in damp environments.
-
Seal the plywood – Applying a waterproof sealer or paint adds another layer of protection.
-
Improve drainage – Ensure the ground slopes away from your shed site so water doesn’t pool beneath.
