If your door is on the end of the building you can achieve more height by using a vaulted truss, If your roof is 7-12 pitch the inside ceiling could be a 3-12 or 4-12 giving you another foot of height over the door. There are other ways to frame your roof to get the same results if you don't want to use an engineered truss system.
I would check with the building dept. at city hall, I think the measurement is made from average grade to midway on the roof, they should allow a height of 5 meters (16 ft) at mid roof on a secondary building.
I haven't seen one of those flip up doors for years, they don't work well with a larger insulated door so the rollup took over the market. You will get a better seal around the door with a rollup than the flip up.
