I think it's 18 ft to the bottom of the roof trusses. The bales are "5x6" but in fact I set my 569 baler for 68" instead of 72" dia to give me a bit of room for error stopping and not stress the baler as much.

Built in 2014, I had the local crew building it to put a (3) 2x6's horizontally between posts all around to keep bales away from the siding.