Most sheds are built with a construction technique that’s known as stick framing. The floors and walls are assembled out of individual “sticks” of lumber (The term sticks refers to standard 2-by construction lumber). Here, I’ll describe the various methods for framing the floor of your shed.

Assembling the joists

nailing the mudsill for shed
Make each mudsill assembly by nailing a 2×8 to a 2×6. Cut both boards from pressure-treated lumber rated for ground contact

The typical floor frame consists of three main parts: mudsill, perimeter rim joists, and floor joists. The mudsill is the lowest wood member in the frame; it sits flat on top of the foundation. The rim joists, also called band joists, frame the perimeter of the shed floor. The floor joists fit between the rim joists, on top of the mudsills, and are typically spaced 16 inches on center. For the best protection against rot and wood-boring insects, be sure to cut all the floor-frame parts from pressure-treated lumber. Most shed floors are framed with 2x6s and 2x8s. The correct size lumber to use will be clearly marked on your shed plans, but if you’re not sure – ask the local building inspector.

Fastening joists to the mudsill

shed joists fastening
Set the 2×6 joists between the two rim joists and on top of the 2×8 mudsills. Fasten each and with three 3 1/2 in. galvanized nails.

The simplest way to frame the floor is to first fasten each mudsill to a perimeter rim joist to form a long L-shaped assembly. Set the mudsill assemblies on opposite sides of the foundation. Next, cut floor joists to fit between the two perimeter joists. Space the floor joists 16 in. on the center to provide the proper support of the shed floor. Nail or screw through the rim joists and into the ends of the floor joists.  

Tip: Here’s a quick, accurate way to determine if the floor frame is perfectly square: Measure diagonally across opposite corners. If the two dimensions are exactly the same, then the frame is square. If not, adjust the frame until the two diagonal dimensions are equal.

Installing the plywood

shed floor plywood installation
Install the remaining floor joists, spacing them 16 in. on center. Nail through the rim joist and into the ends of the floor joists.

Once the floor is framed, cover it with plywood, which is easy to install, affordable, and surprisingly strong. Plus, the large sheets create a very smooth, flat surface, which makes it easy to roll, drag, and push objects across the floor. Use 3/4-inch-thick ACX plywood, which is exterior-grade plywood that’s well suited for use as a shed floor. Fasten the plywood to the floor joists with 1 5⁄8-inch decking screws or 2-inch (6d) galvanized ring-shank nails. And if you’ll be storing heavy equipment in the shed, consider using tongue-and-groove plywood, which locks together along the edges to create a rock-solid floor.

Tip: Make the plywood floor of your shed last longer and sweep up easier by applying two coats of enamel deck paint. 

Other Popular Types of Shed Flooring

Plywood is definitely one of the most common types of shed floors, and it has many advantages. But there are other types that people seem to love just as much.

Timber tongue and grooved planks are a great option for shed flooring. Timbers tend to be strong, and they are much more attractive than simply pouring concrete or using plywood. A lot of people find them to be much easier on the feet than other types of flooring as well. But timber tongue and grooved planks do have their downsides. For example:

  • Timber tongue and grooved planks will eventually rot.
  • Pests that destroy wood will be attracted to them, potentially causing a lot of damage.
  • When they are exposed to water, they can warp easily. This includes water from rainstorms and from wet, muddy boots.
  • This type of flooring can be scarred if heavy objects are rolled or dragged across it.

Oriented Strand Board, or (OSB), is a standard type of flooring used for sheds and other structures. Many homes are built with OSB as a subfloor. But while it might be useful, OSB has one big downside. It is extremely ugly. As you build your shed, if looks are important to you, you might want to choose a different type of flooring. It may be cheap and strong, but it also prone to breaking down and rotting when it is exposed to the elements.

Don’t Let Building Your Shed Floor Intimidate You

Building a shed doesn’t have to be difficult. While the way you build your shed floor is important, if you follow our instructions, you’ll have no trouble building one that is attractive and functional. It won’t be long and you’ll have a beautiful shed that fits your needs.

Joseph TruiniJoseph Truini is a host on the Today’s Homeowner TV show and co-hosts the weekly Today’s Homeowner Radio Show. He has written three best-selling shed-building books and lives in Roxbury, Connecticut.