My 30' separation between the house and my shop/hangar, can be brutal at times. My walk path makes it more like 45'-50', with a set of steel stairs. In the winter, there is no walking over with a cup of coffee and wearing slippers, ha ha. I'm on a mountain side with lots of wind etc. I do like to think that if one structure caught fire, maybe the other wouldn't, but who knows...and that's what insurance is for anyway. I built both the shop/hangar and then the house out of pocket, about a year in between, so two separate structures helped me there, two smaller costs instead of one large one. I REALLY wish I had engineered in a underground passway, a tunnel, between the two structures. On this mountain, anything outside creates drifts, and problems. A tunnel with the roof flush with the ground level would work...then I could do the slippers while carrying a cup of coffee thing! But doing it now, I'd be digging up all my utilities, my entire electrical panel, and my well line, so it's easier to just have an old coat and pipe mover boots by the door and tough it out. Sure beats driving 20 miles to a rented hangar at the towered local airport though! Probably even easier to just buy a big all in one home/hangar combo someone else has built!
Neal Salmi's place in Townsend Mt. is the most deluxe I've ever seen, someone needs to jump on it.