Im with dom...I tried setting the actual grid to metres but Maya didnt and doesnt like it for some reason...which still has me perplexed. Good luck with it mate! Oh and to keep it in scale I would make a block (up to you) that is 1.8m tall and about 0.5 by 0.5...that will give you rough human dimensions. Better still research on the kind of building it is...they may give out dimensions...and you could make a template block and use that? thats what I do in general now.

cheers bullet