I've been mulling over different ways to make a sectional city using 6 inch square sections of cardboard as the base with the roads exiting in the middle of each side so I can switch the layout around.
I'm not sure the cardboard is going to be a good base but I chose it because it's thin. I may look for a cheap way to use plastic card (maybe from milk jugs).
Anyway, the first section I'm working on is going to be bombed out... requiring ruins.
After looking around for various ideas I chose to go with cardboard again from a pasta box. My first building are going to be just ruined shells so all I need are a few walls with some windows and doors. At this scale the cardboard should be thick enough to represent the wall.
I began by drawing out the windows and cracks on the cardboard. At this scale 1 mm approximately equals 1 foot. So my windows are about 5 feet off the ground and 3x5 feet in size.
Once they were planned out. I used scissors and a razor to cut them out. Then I scored the places where the walls would bend with the same razor before actually making the bends. The top picture has three bends (The three vertical lines) and the second building has only one bend in the middle.
When I was cutting them out I made sure to make tabs at the bottom of each section to use later for gluing to the base. These had the added advantage of helping the building stand when I placed it on the table for photographing as you can see in the third picture. The forth picture shows the same building with a GHQ miniature for scale.
Once I cut out both buildings I cut a 6 inch square from another thicker cardboard and glued the two ruins down and let them dry for the night.
Then I began detailing the base. I used filler to create craters in the buildings (which caused warping and so I had to change the base to corrugated cardboard [and something heavier might even be better]). I used scraps of card and other bits to put in and around the craters for rubble then covered sections with sand to represent the dirt flung around by the explosion.
You can also see the roads in the picture. I printed these out from Microsoft Paint, cut them out and glued them down.