This is an interesting question alfarigel. I think a correct answer must refer to the "limit of resolution" and this is depending on the diameter of the telescope. My telescope is a relatively modest instrument (diameter is 200 mm). For something on the Moon, the limit of resolution is rougly 1.1 km (possibly 1.2 km, not much more). There are formulas and tables for doing such calculations. These are two examples:
http://jumpjack.altervista.org/telescopio.html
I cannot see a small house, for sure. A big building would have to be more than 1.1 km, which is really very big, and it would look like a little dot for me, at the limit of resolution.
Let's say that I can see only very large features on the Moon!