You have to see these pieces in person to see how highly detailed theses pieces are, and how well painted,there incredible.
I talked with him a bit about how they are made and he uses all kinds of materials in his dioramas but for his buildings he seems to like that poster board stuff like the kids use to do there school projects if you know what i,m talking about, I don,t know the correct name for the stuff but its about a 1/4in. or less in thickness.
For his bricks he uses those pre-cut plastic sheets you can get in most hobby shops that come packaged up already cut into strips of various sizes and then just cuts them into brick sized pieces and glues them all on

lots of work but the finnished result is incredible looking realistic brick finnish.
When he has a finnished piece he makes a mould and sells them as kits made out of some kind of plaster or something similar.