Phase Three: The Shell Trailer/Floor:  Order Your Trailer: know what you want and make it clear. Unless you’re getting a trailer from a tiny house company, you’re going have to explain exactly what you want and why it’s important. Do your research beforehand and have a bulleted list of your specs. You’re probably going to want as much width as you can get, evenly spaced cross-members, a low deck, metal flashing underneath, leveling jacks, no railings, no decking, no ramps, and a high weight rating, to name a few things. Place your order 4-8 weeks before you want it to arrive, depending on the company’s wait time. Decide whether you’re going to pick it up or pay to have it delivered.

All-Threaded Rods  Hire a Welder: when you have a pick-up or delivery date confirmed, contact a welder about an on-site job and make an appointment. The welder should have standard 5/8” all-threaded rods that they can cut to length for you. Make sure the rods are long enough to go through your floor and the bottom plate of your wall. The welder might have nuts and washers for sale, but it might be cheaper to buy them from the hardware store. When the trailer arrives, you’ll need to mark the locations where you want the rods welded on. Consult your framing plans to make sure the rods don’t interfere with any studs. Also, if you plan on using hurricane ties that secure the rod to a stud, make sure the rods are the right distance away from studs. It’s best to have a rod every 6’ or less. If you’re using 2x4 framing, your rods should be ¾” in from the edge of the trailer (as long as your walls will be flush with edge of the trailer) so that the rod ends up in the middle of your bottom plate. Be aware that your trailer might not be perfectly square. Any welding should be done before insulation or a subfloor so as to not burn either.

Insulation  Buy Insulation or Make an Appointment: after researching different insulation options, you should have decided what kind you want. Calculate how much you’ll need for any kind other than spray foam and order it or pick it up from a hardware store. Do this before your trailer arrives in case you do need to order the insulation. If you need fill gaps, like with rigid foam board insulation, buy some foaming sealer as well. If you decided to go with spray foam, after you know the pick-up or delivery date of your trailer, make an appointment (after the welder) for them to come and spray the trailer. You won’t be able to be in the area for 24 hours afterward, and you should have 30’ of clearance on all sides.

Estimating  Estimate Materials: do some math and/or use another tiny houser’s numbers to estimate how much you’ll need in the way of adhesive, screws, plywood, and more. Some people use sill sealer between their trailer and subfloor. Depending on your insulation you might need a vapour barrier.

Hardware Stores  Buy Materials: you might want to check a few stores to see which has the best pricing. Don’t be afraid to talk to the employees; they’re there to help! For plywood or OSB, consider weight and how far apart your cross-members are. You might want to do some research. Tongue and groove creates a stronger floor, but is more difficult because of the all-threaded rods. Make sure the adhesive you’re buying adheres to wood and metal. Try to find the longest reposition time. Make sure the screws you buy are meant to drill through wood then metal and ask if you need to pre-drill. Buy more than you think you’ll need. Also, make sure you have a vehicle that can fit 4x8 sheets!

Getting Started on the Floor  Spray Foam: it’s best to get the insulation sprayed after the welding. It can’t be raining when they do it. After the foam cures, it will reject bulk water, but you’ll still want to get your floor down as soon as possible. You can even cut and dry-fit your wood before the insulation is in if you have time before the appointment.

Dry-Fitting  Cut & Drill Plywood: if your cross-members are evenly spaced, it shouldn’t be too difficult to put down large sheets, but if they aren’t you’ll need to do some calculations. Plywood and OSB are meant to be perpendicular to the strength axis – the crossmembers. So even though your trailer is about 8’ wide and so are the sheets, you shouldn’t lay them like that. Tips: You will need another person to help you. Even if you can carry plywood by yourself, you’re going to need someone to help you put the sheets into place and it’s helpful to have someone holding sheets as you cut. You should stagger the seams to avoid creating a flex point. Try to create as little waste as you can by planning your sheets in advance. Measure carefully. Table saws aren’t really practical for cutting plywood. You should only rip on table saws and even with two people, maneuvering would be difficult. A circular saw works well. You can make a fence or follow a line by hand. You should cut with the good side down. Allow for a 1/8” gap between non-T&G edges. For drilling holes for the all-threaded rods, you should drill with the good side up because the bottom is going to splinter more. Use a drill bit that will make a hole big enough for the weld around your rods so that the plywood will lie flat. If you chose tongue and groove sheets, be aware that some of the holes will need to be oval to allow for sliding, and you’ll need to plan the order you’ll put the sheets on and which ones will slide.

Securing Your Subfloor  Glue & Screw Plywood: when you take off your dry-fitted sheets in reverse order, mark around them with chalk so you’ll know later where each sheet should go. Number the sheets, so you know what order they go back on. Also mark all your crossmembers on the side of your trailer so you’ll know where they are once the wood is down. If you’re using an insulation other than spray foam, it’s probably best to put in the insulation as you go. That way, if it rains before you get all of your sheets on, you won’t ruin insulations like wool or fiberglass. It’s a good idea to dust off your crossmembers and your wood before you glue; adhesive sticks best on clean surfaces. Also, read the instructions on the adhesive. Your screws should be six inches apart at the edges and 12 inches apart in the middle, the field. Be aware: drilling into metal is not quick! You’ll need an impact driver, and preferably a friend with another impact driver to help.

Trailer/Floor Steps  Order Your Trailer  Hire a Welder  Buy Insulation or Make an Appointment  Estimate Materials  Buy Materials  Spray Foam  Cut & Drill Plywood  Glue & Screw Plywood