Eave height and the door opening. Eave height is measured at the sidewall where the roof meets the wall, and it sets the maximum practical door height. Catalog eave heights for metal building kits commonly run from about 8 to 30 feet. Equipment does not care about eave height as such — it cares about the clear opening under the door header and the headroom needed to raise a dump bed, extend an auger or clear a grain cart. The right way to arrive at a number is to take the tallest machine in the position it will actually occupy inside the building rather than its transport height, then add the clearance an operator needs to work around it. Where a supplier quotes a familiar eave height for agricultural storage, that reflects what is held in stock, which is a supply fact rather than a design input. The door is then engineered as an opening in a structural wall, and that framing has to be resolved before fabrication rather than cut in afterwards.