How much room does a gym need?
Start from your kit, not the building. An Olympic bar is 2.2m end to end and needs space to load plates at both ends, so a rack and bench want a width of around 10ft before you add a cardio machine or a mirror wall.
Height matters for overhead work. Inside, a pent stands 1887mm at the high front wall and 1757mm at the low rear wall, so put the rack towards the front; an apex gives 2285mm under the ridge. Sizes below are the ordered nominal sizes, and the real external footprint is a little different, so lay your kit out on the lawn first.
