1. Build the Pallet Floor
First choose a flat stable surface to build on like a concrete slab or flatbed trailer. Count on the house weighing between 4000 and 5000 pounds when complete and choose your trailer carefully.
I’m suggesting this arrangement for the shipping pallets because it would most likely fit on many common double axle trailers you’ll find. It also is less than 8′ wide which is the legal limit for trailers in many states. In the drawings you’ll see the steps for bringing the pallets together.
In the first drawing I’m simply showing that it’s best to prepare the pallets by attaching 2x4s to the open ends of the pallets. This makes the pallets stronger and gives you four sides to nail, screw, and bolt to. You can free the necessary 2x4s from other pallets by cutting through the nails with a reciprocating saw. This is the fastest way to dismantle a shipping pallet and will leave you with the most usable wood.
Here are the prepared pallets ready to connect. In my tiny free house project I’m finding it useful to screw the pallets together first and then bolt them once the pallets are connected. It feels quicker although a bit redundant but seems to work well. You may also find it useful to have a couple clamps around to clamp the pallets together as you make the first attachments. Many shipping pallets are made from hardwood and getting screws to bite into the wood, saws to cut, and drills to drill can be tough. Better to use quality tools that plug into the wall or generator. Leave the little battery operated tools to small home repairs.
2. Lay the Floor
Now attach 4×8 sheets of plywood or another sturdy sheet material to the pallet subfloor. You might also want to take the extra step to sheet both sides of the pallet floor structure and insulate it. This will give you a very strong and sealed base for your house. The thicker the plywood in the floor the better, especially the surface you walk on.
You’ll notice that the plywood overhangs the pallets a little. Just cut off the extra plywood. Be sure to save these small pieces though, you’ll most likely find a use for every piece of extra wood. I’ve been using screws to connect all the wood in the tiny free house simply because I think it’s stronger and the house is mounted on a trailer.
3. Raise the Walls
Once the floor is down and solid start lifting prepared pallets into place. By prepared I simply mean pallets with 2x4s screwed or nailed onto the open ends. Doing this quickly gives you four sides of the pallet to screw or nail into. It also makes the pallet stronger.
If you use non-standard (40′ by 48′) pallets you may find your walls are a little long and need the ends of the pallets cut off. This is easy to do with a reciprocating saw. Then just slide the 2×4 back in between the slats and screw or nail the slat boards back to the 2×4. Be sure to clean the slats ends off the 2×4 before doing this of course.
It’s also a good idea to stagger the pallets to avoid one long weak horizontal seam. This is easily done by cutting pallets in half. Be sure to add 2x4s onto the open ends of the pallets. Also note that you’ll have two extra horizontal 2x4s in the wall sections with the cut pallets which will add to the height requiring you to trim a little more off your cut pallets.
The walls require 24 standard 40″ by 48″ shipping pallets. If you have sturdy lighter weight pallets this is better for the walls. Place the heavier of the pallets lower in the wall simply because it will keep the center of gravity lower.
4. Add Windows and a Door
Once the walls are up get out the reciprocating saw and cut out spaces for the windows and door. Use new 2×4’s or some from dismantled pallets to frame rough openings for your windows and doors. It’s best to build the window and door bucks from your best and longest wood since most doors and windows require strait and plumb surfaces.
Once your window and door holes are cut, slide the 2×4 window and door bucks into place. You’ll probably need to build them into place instead of prefabricating them. The other important thing to do is square up the bucks before fastening a lot of screws. I would put one or two screws in first, square it up, and then fasten a small piece of plywood to the surface of the buck to hold it square while you work. Later these temporary braces can be removed. They are added only to help you keep the window and door openings square while working.
5. Building the Walls and Roof
Before adding siding or insulation be sure to bolt the pallets together. The stronger the connection between pallets the stronger your house will be. I would not trust nails or screws alone. I would use some bolts as the final connector. Also be sure your walls are strong before lifting the roof pieces into place.
Another step you might want to take (not illustrated) before raising the roof sections is to add a top plate on top of the walls to tie all the pallets together. This is usually done with long 2x4s.
6. Pitched Roof
My preferred roof design it a pitched roof but it is more difficult to build than the shed roof and is purely an aesthetic choice. It also adds extra vertical space for a sleeping loft.
To build the pitched roof I would attach two pallets together first while standing inside the house and then lift the section into place. This will also help you keep the pitch the same because you’d be doing the tricky work on the flat surface of the floor. One strong person could lift it into place but two or three people would be much safer and easier. It would also be good to notch the pallets to fit the top of the pallet walls before lifting them into place. Be sure to lift the end sections into place first before lifting the last center piece or you’ll have to go outside the house to lift the last end section.
A steeper pitch could be done but it would require longer pallets or splicing normal pallets together. It would also make the whole house taller and if you’re building on a trailer you’d need to do the math and keep the maximum trailer height in mind as you made your final decision on pitch height. Every state has different trailer height limits but 13.5 feet seems to be very common.
7. Shed Roof
Here is another way to build the roof. The high end is about 8 feet high, the pitch illustrated is a 3:12 pitch (drops 3 inches for every 12 inches horizontally). The lower wall is about 80 inches high. This design makes the roof easier to build for a few reasons.
The roof is shorter making it easier to build and repair. It’s a single shed style pitch requiring only flat pieces of corrugated roofing or a simple layer of asphalt shingles. If you build on a trailer it might want to use metal roofing or risk loosing shingles at highway speeds. There is also no peak to cap or complex framing. The only draw back is that the house is not as good looking and if you wanted to build a loft there is not as much vertical space to work with.
If you use pallets be sure to stagger the panels just like the walls or you’ll have a very dangerous seam right down the length of the house only supported by bolts. The pitched roof also has this problem but the pitch itself helps support the roof and the bolts are not being relied on in the same way.
In this flat roof the bolts are under a shearing force which is basically weight that is trying to snap them in half. Bolts, nails, and screws are stronger when the force on them is along their length, pulling at both ends. Which reminds me… always use washers on both ends of your bolts to prevent the bolt head or nut from coming through the wood.
8. Interior and Exterior Sheathing
Now that the pallet walls are up and the roof is on it’s time to sheet the interior and exterior. I’d use plywood since it adds a lot of structural strength to the tiny house. If plywood is not available use whatever you can find. 4’x8′ sheets of the most weather resistant material you can find is best.
If you use surface mount windows this will give you an opportunity to cover the window flanges with the exterior sheathing. If house wrap is available adding this to the exterior of the pallets prior to attaching the exterior sheathing will make a tighter seal.
The most important part of this step is to try and make your tiny pallet house as air tight as possible. The more air tight a house is the warmer and cooler it will stay. If you have insulation available by all means add it before sheathing the interior.
I personally think metal roofs are best. They might be louder in the rain but they sure stand up to the weather better. They also don’t tend to fly off like asphalt shingles when towing your tiny house down the highway. Always lay down roofing felt (a.k.a tar paper) before applying the final roofing material and if flashing is available by all means put that around the edge of the roof on top of the roofing felt.