4 Best Types of Wood For Building a Shed

When you decide to build a shed for storing tools or for some other purpose, your choice of wood can make the difference between one that you’ll still be using in 20 years and one you have to tear down or renovate in half that time. Of particular importance is the wood you use for the foundation — and yes, your shed needs a solid foundation if you want it to last.

Case in point: I built a shed on a foundation of railroad ties some 15 years ago. While the ground underneath the shed settled, forcing a remedial leveling operation, the foundation itself remained intact because of the wood; railroad ties are heavily treated to resist rot. Railroad ties aren’t common everywhere, and don’t worry if you don’t have access to them because every lumberyard carries treated wood that will last just as long.

The wood you use for the rest of the shed isn’t as critical as the foundation wood, and because it’s a shed, there’s no need to overspend on it. Ahead, with some guidance from Josh Kou of North Castle Hardwoods, you’ll learn about the best types of wood to use for your shed, whether you plan on using it as a place to store your garden tools or as a recreational outbuilding.

Building the Foundation

There’s a lot to be said for building a shed on a concrete foundation, but if you don’t want to go to that trouble, a post-and-pier structure works just as well. Raising the floor above grade protects from flooding while preventing the shed from going off-level when the soil settles or erodes. And it’s easy to build.

Even though it’s off the ground, the foundation still needs to be constructed with pressure-treated (PT) wood. So do the posts, but because they’re in direct contact with the ground, you need to make them with wood rated for ground contact. This type of PT wood, which bears a stamp identifying it, has a higher concentration of preservatives than wood rated for above-ground use. If you build your shed close enough to the ground for the beams and joists to be touching, the wood you use for them should also be rated for ground contact.

Constructing the Frame

Every wooden shed has some kind of underlying wall and roof frame, and you don’t need to make it with expensive wood. Just use conventional framing lumber, also called “construction-grade lumber.” It’s usually fir or spruce, and its actual dimensions are a half inch shorter than the nominal dimensions, which are the dimensions before the wood has been planed smooth. The good old 2×4, for example, is actually 1-1/2 inches thick and 3-1/2 inches wide.

It’s common to build shed walls with 2X4s, and you can save money by purchasing “studs,” which are 92 5/8 inches long and produce walls 8 feet in height when combined with a 2×4 top and bottom plate. Because they are pre-cut, they’re priced by the piece rather than by the foot, resulting in a lower per-foot cost than buying longer boards and cutting them to the lengths you need. Studs are bargain-priced because they are considered utility lumber, and many in the pile at the lumberyard are warped or twisted. Check each one carefully and reject any that aren’t straight.

Given the size of most backyard sheds, 2x4s can usually be used for both the wall and roof frames, but if you need a sturdier roof to support snow in the winter, you might want to upgrade to 2×6 fir or spruce for the roof framing. Either way, you’ll find what you need at any lumberyard or building supply outlet.

Roof, Walls and Floor

OSB and exterior-grade plywood are two choices for covering the framing, and there’s a third choice for siding, which is the one I prefer.

OSB

Oriented strand board (OSB) is made of softwood chips glued together in a semi-random pattern. It typically comes in 4 x 8 ft. sheets. While 7/16-inch thick OSB does a fine job structurally, it doesn’t age well when exposed to weather. You wouldn’t want to leave it exposed anyway because it’s spectacularly unattractive, so you always cover it with additional roofing and siding materials.

Exterior-grade plywood

Exterior-grade plywood is stronger and more weather-resistant than OSB. Kou explains that several grades are available, all identified by the letter “X” (for “ex”-terior). Five grades, AAX, ABX, BBX, BCX and BDX, have a good side that you can paint, but the more common and less expensive grade, CDX, is suitable only as an underlayment. When you use CDX for siding, it has to be covered with something else, such as vinyl, aluminum or wood. The roof always gets covered with shingles or metal panels, so CDX is an ideal material for roof sheathing,

You’ll find that 1/2-inch thick material works well for wall and roof sheathing, but for the floor, you’ll need plywood that’s at least 5/8-inch thick. Ordinary exterior-grade plywood is made with weather-resistant glue, but the wood itself is not particularly rot-resistant. This is why pressure-treated plywood is best for a shed floor. Even a floor raised off the ground a bit will last longer if made with pressure-treated plywood.

T1-11

My number one choice for siding for a shed is T1-11, which comes in three thicknesses: 3/8, 5/8 and 3/4 inches. It’s basically exterior-grade plywood, but one side is milled with a rough, decorative texture suitable for painting. It comes in 4X8-foot (and longer) sheets that are completely weatherproof, and if you use 5/8-inch thick material, it’s all you need for siding. Just staple tar paper or house wrap to the framing, hang the T1-11, and you’re done…almost.

Trim

Trim on the corners of the shed, under the eaves and around the doors and windows adds the final decorative touch. Don’t be tempted to save money using materials intended for interiors, such as pine, fir or medium-density fiberboard (MDF). They won’t last.

The best trim materials are redwood and cedar, either smooth or rough awn. In most cases, you’ll need 1-inch material (actual thickness 3/4 inches). I most often use 1X4-inch boards, but occasionally, I’ll use wider 1X6-inch ones for the soffits and narrower 1X3-inch boards for doors and windows.

• Pro tip: If you’re going to paint your shed, you’ll do a cleaner job by painting the siding before you install the trim and priming and painting the trim before you hang it.

About the Expert

Josh Kou is the shop manager of Chicago-based North Castle Hardwoods. He is a second-generation lumberman who has worked with wood all his life.