I have a 14x14 wash stall, 14x14 grain room and a 14x20 tack room. I don’t tend to x tie in it as my guys all stand, however its a bit of wasted space, 10-12’ wide would be plenty. The tack room is a good size, but if I had more boarders it would get small fast. the grain room has a lot of wasted space too.
Things I wish I had instead: storage for 6-8 bales of hay for easy access and wheelbarrows/muck tubs… currently there in an extra stall. I don’t like them in the grain room as its messy and the grain room is hard to clean easily. as such with the wash stall as i don’t want the hay to get wet and the wheelbarrows are a safety hazard there.