The cost of converting a box trailer into a camper using new or salvaged parts is likely to exceed the price of buying a used travel trailer. However, if you have a box trailer that is surplus to requirements and enough of the necessary appliances and fixtures on hand, your conversion can give a new lease of life to otherwise wasted materials. You will also have a camper that was built exactly to your own requirements, and you can chose any standard of provision from basic shelter and storage to sumptuous accommodation. Most box trailers have double rear doors, so they lend themselves well to conversion into toy haulers. Always have the weight of your improvements in mind as you go about planning your project.
Determine how basic or luxurious you want the finished camper to be. You can go from an air bed on the floor for a bedroom to a futon or a platform bed that takes up half the trailer; you can have a camping stove and a cooler as a galley, or fit a full 120-volt household kitchen. Spend some time at salvage yards that have accident-damaged travel trailers and RVs in stock to give yourself ideas, and then purchase what you feel you can use.
Sketch out a drawing of your project, transferring the actual measurements onto the plan to see how everything will fit together. Graph paper works well for this. If you are buying a box trailer specially for your conversion project, your plans should be finalised before you make the purchase so you know how large it needs to be.
Fit your windows and roof vents first. The windows should not be in your sleeping area; good places for roof vents are above the kitchen and bathroom areas. Next glue sheet insulation material to the inside of the walls, then line the box trailer with lightweight sheets of wall panelling screwed to the structural uprights. Use a heavy floor covering to decorate your camper and double as sound and heat insulation.
Install wiring circuits, balancing what is available against budgetary constraints. A 12-volt deep cycle battery powering a basic lighting rig and one or two power outlets can be enough for a trailer used as a hunting cabin, or you could install a 120-volt system with a shore power cord feeding a circuit breaker box and a full array of household appliances. The plumbing is equally a matter of personal choice, with a simple gravity-fed sink for cooking and washing as one extreme and city water hookups to a full-size shower and toilet as the other.
Build interior dividers from lightweight plywood to give the inside of your box trailer some separated areas, then fix cabinets and shelves to them. Hang curtains from curtain rails for privacy, if the size of the trailer limits the space you can divide. Locate storage near the doors, and if you are using the rear of the trailer as a toy hauler remember to fix heavy-duty hooks where you will need to attach the ratchet straps that hold the machine in place while you are under way.
Too much weight at the front of the box trailer can increase tongue weight and cause the tow vehicle to lose steering traction, and too much weight at the back of the box trailer can make it fishtail at surprisingly low speeds.