Door height
Seven years I had a building built 14" tall so I could get a larger RV at some point. I knew nothing about doors, floors and sidewalls, but I told the large building company what I wanted. Bottom line...
Forum Discussion
Since you described the roof as having trusses, then I'm assuming that means wood trusses. If so, they are probably flat on the bottom and therefore limiting the height. You could remove the roof, replace the trusses with cathedral trusses and get more height in the center area. I did that years ago. With a 16 ft wide building, the outer 4 ft on each side was only 11 ft tall at the edge (which is fine for slideouts), the center 8 ft was 12.5 ft high. The front wall and door would also need replacement. With the door height you have now, there are basically no late model fifth wheels that can work, which means you are limited to TTs.
Finally, if you are going to extend the depth of the building and can make that extension at the front, then you might be able to just build the extension taller. But that limits you to fifth wheels that don't have a flat roof (front to back).
Finally, if you are going to extend the depth of the building and can make that extension at the front, then you might be able to just build the extension taller. But that limits you to fifth wheels that don't have a flat roof (front to back).
