Just FYI, in case you haven't noticed it, there is a slight bug with the housing tool. If you're trying to fit into a tight place that you think something should fit in, you're probably having problems on the E/W axis, not the N/S one. The housing tool offsets by at least 1 tile to the west, and on larger sized buildings, sometimes 2 or 3.
So, basically try placing, but when it looks correct on your screen (ie: it should fit), try moving your cursor one tile east (on the diagonal) and try again. If that doesn't work, try 2 or 3...
If it still doesn't work, then chances are it's something else.