Saving money is the primary reason to build a shed with pallets. Add some affordable materials and you've got a shed you can be proud of, at a fraction of the cost. Pallets aren't pretty, but they're strong because they're made from hardwood, and provide reliable building materials.
Pallet Types and Sizes
The standard GMO, or Grocery Manufacturer's Association pallet, is the most common pallet in the United States. It measures 40-by-48 inches, and it doesn't require a ton of them to build a significant shed. Other pallets, such as pallets for paint or beverage containers, may be a few inches difference in size, but it's not enough to make a significant difference in how you assemble it.
Where to Find Pallets
Visit local businesses for cast-off pallets. Grocery stores, feed, seed, furniture stores and warehouses are all good candidates for used pallets, and you can usually get them for free.
Pallets have distinctive parts. The horizontal planks that make up the surface are deck boards. The 2-by-4 runners underneath, perpendicular to the deck boards, are called skids or stringers. Plan on building the walls with the deck boards running horizontally, or parallel with the ground. This positions the skids' vertically, side-by-side, so the pallets can be joined more efficiently, and makes the shed more structural.
Sheds need good access. A double door is one way to provide good access. Don't worry about framing it to fit an existing door, plan on building a custom door out of two pieces of CDX exterior plywood. Standing upright, plywood is tall enough to reach from the floor to the top of an 8-foot-tall shed. Use simple gate hinges to hang the plywood doors.
Build The Lower Wall
The shed requires a lower wall, with another wall stacked on top, to reach about 8 feet. Lay the pallets side by side and build the walls flat on the ground. To fasten them together, either drive 3-inch screws randomly through the skids, or drill holes and use bolts with nuts. Both methods work fine.
Footings and Floors
Simple, impromptu pallet shed walls might be placed directly on the ground, but if you want more longevity, getting the walls off the ground is important. Place a row of shallow cinder blocks around the perimeter, or space them as needed to support the shed walls.
Drive a steel T-post at the corners, or a standard piece of rebar into the ground. Stack the first wall on the blocks, and use metal straps with screws or bolts to secure it to the rebar or posts. With the help of an assistant, lift the second section on top of the first, and square it. If it's too big to lift, it's fine to build the upper section one piece at a time, on top the lower section.
Options for Joining Walls
There are two options for joining the walls, depending on your application. A more finished shed would include them both.
Fasten the lower wall to the upper wall by inserting 18-inch two-by-fours into the pallets, vertical alongside the stringers, spanning equally between the upper and lower walls. Drill and bolt the two-by-fours to both stringers, or screw them on to secure the lower section to the upper section.
A more substantial, finished shed would include OSB, or oriented-strand board, screwed around the perimeter on the inside to serve as sheathing, which adds strength and permanence. Sheathing is also advisable on the outside. If you do plan on sheathing the outside, use CDX plywood.
Corners and Posts
Pallets lend themselves nicely to 90-degree corners. Just overlap one pallet wall at 90 degrees and screw or bolt them together. A more substantial corner might include a two-by-four screwed into both pallets in the corner, or even a treated four-by-four post --more expensive -- planted in the ground. A simple corner might include a steel T-post driven into the ground to add stability.
Flat or Slope
It's difficult to build a sloping roof using only pallets. Purchase some long two-by-fours, about 10 feet long. Screw one vertically in two corners, to extend one end of the shed higher than the other to give the roof a slope. Add roof joists normally, sloping to the other wall. Screw one-by-four pine boards perpendicular across the joists, and follow up with recycled tin.
If you're building a garden or utility shed, your shed could be considered done at this point, with only a dirt floor. But pallets can also be used as flooring if desired. Pallets won't stand up to direct contact with the ground, but by treating them with borate -- a safe alternative to wood treatment -- the floor is moisture and insect resistant. Top the floor off with a layer of OSB if desired, and you've got a smooth floor that should last for years. Spray borate on all exposed wood surfaces, including inside the pallets, for the best weather-resistance possible.