The main structure of the house is a steel frame made out of 30x30mm box 1.5mm mild steel. I made the steel frame and had it galvanised. I had to make the frame in six main sections to fit in the galvanising tanks. I also made six storage boxes that fit between the chassis rails, one of which is the external wood store and the other 5 are accessed from inside the house. Once these sections were made it was fairly easy to bolt the house today in less than a day.
It took 4 months to design and build the frame. It partly took this long because I had to find the windows and door and work out the bed system at the same time, so I could make the frame specifically fit them.