When I built my first tiny house I used a standard equipment trailer with just a few special requests. These requests included leaving off the ramps, not having a dovetail (which is a slanted back which helps when loading heavy equipment like tractors), and using heavy duty axles. I actually forgot to have them leave off the front guard (which is a piece of metal on the front of the trailer that stops your equipment from rolling too far forward). That ended up not being that bad of a mistake since it made me build the front compartment which I ended up really liking and has stuck with several of my other designs.
While building on a standard trailer is definitely not a problem, there are a few things that I have had changed over the years for our houses to improve the way they are attached as well as to make the trailers a little lighter. I’ve been offering these trailers to others as well if they contacted me directly (which several have), but I recently decided that I needed to set up something a little more formal so that anyone who was interested could get one (without knowing the special handshake ;).
So we’ve introduced our new line of trailers specifically made for tiny houses over at http://www.tinyhomebuilders.com/tiny-houses/Trailers
These trailers have many of the special requests of my first trailer as well as a few more. Most notably are the steel flange and the metal deck replacement.
A typical trailer has wood decking that runs the length of the trailer. That decking is supported by steel beams (cross members) that run perpendicular to the decking and attach to the sides of the trailer. Since the subfloor of your house needs to be attached to the metal of your trailer you may think that the cross members would be a good choice. The problem with using those is that since they run in the same direction as the floor joist, you would have to perfectly line up the floor joist with those beams. Those beams are also pretty far away from the subfloor since they are under the wood decking, which would require a really long bolt. What you really need is metal that is running perpendicular to the subfloor joist and is right up against the subfloor. While the trailer side beams match both those requirements, it’s a pretty thick metal and is usually a ‘C’ channel which doesn’t give you much room to drill. So the best option is to just add brackets (that is how we used to do it) or a flange to the sides.
Why not pre-drill the flange or weld the bolts to the trailer?
While having the bolts welded to the trailer may seem like a good thing, it’s actually a pain to work with and doesn’t give you a good way to attach the subfloor (when the bolts are on the back and front). If the bolts are welded to the sides of the trailer you’ll need to make sure that you have a joist in that exact location to attach to it (not exactly builder friendly). This can require you to add an extra joist or change your plans around. It can also be a pain to work with a fixed bolt since you will need to predrill your wood before putting it in place. This can be hard to line up correctly and you will need to do so before you attach the board to anything. While it can be worked around, as a builder, I just don’t want that hassle.
The flange on the other hand allows you to put the bolts wherever your joist end up after you’ve constructed the subfloor. That’s why we don’t predrill the flange either. While it may seem intimidating to drill your own holes through the metal it is actually quite easy. It doesn’t take any special tools other than a standard drill and a good drill bit. Others like to talk about plasma cutters and special drills to scare you into thinking that you can’t do it. But you’re about to build a house, what’s a few more holes to drill.
Bolts welded to the back or front of the trailer are even worse. In these locations the subfloor doesn’t typically hang over the edge, so what is the bolt supposed to attach to? Cantilevering the subfloor over the back edge just so you can accommodate that bolt seems a little unnecessary.
Finally, the flange also increases the width of the trailer, thus reducing the amount that the subfloor needs to extend unsupported over the edge of the trailer. More support is always a good thing.
Replace the wood decking with metal beams
By replacing the wood decking with metal beams, we eliminate some of the weight of the wood decking and provide another place to bolt the trailer to. Not to sound too redundant, but these beams are up against the subfloor and are perpendicular to the joists.
Basically what it comes down to is you want to have metal on your trailer that runs the length of the trailer that will give you a good place to attach your house too. If your trailer doesn’t come with those metal surfaces, you’ve going to have to add them.
I personally designed these trailers for what I want and need, and it’s what we use for our houses.