Er... well, I wouldn't say "one hundred foot building" in case people thought it was some kind of centipede...
Although it's commonplace to say "foot" instead of "feet" in those circumstances, strictly it's incorrect. So if you're writing it in dialogue, first person or very close third narrative, you can get away with it; in ordinary narrative I'd go with "feet".
EDIT: pipped to the post!
Although it's commonplace to say "foot" instead of "feet" in those circumstances, strictly it's incorrect. So if you're writing it in dialogue, first person or very close third narrative, you can get away with it; in ordinary narrative I'd go with "feet".
EDIT: pipped to the post!