The basic method, as far as I can see, is just to try visualizing structures that fit. I can easily obtain the maximum of 16, but I can only get a minimum of 8 if I allow the structure to be disconnected (some blocks don't share a face with any other).
The rules are not clear, as to me a "house" would be connected, but they don't define it. It's also implied, I think, that blocks can't float in midair or be glued to the side of another. (The grammar could be improved, too.)
The hardest part, especially for some people, will be to visualize a 3d structure. One way is to draw a "floor plan" to keep track of how high it is at each location, trying to make sure the maximum height in each row or column is appropriate.
Here is my maximum, color-coded by height:
View attachment 24543
I'm sure there are better ways to solve these.