Because I wanted to build it so it could be moved down the highway or at least have that option. This limits you to 13’6″ in height and 8’6″ wide. Most of these are built on trailer frames. I thought I would too but the $3500 price tag needed to be spent building the place first. I did build it on skids so a rollback has a chance to load it. The width restriction is what makes designing tough. A 10×15 footprint is easier to layout and having 18″ eaves looks so much better than none.