Open buildings, used as garages, market stalls, workshop, storage or open walkways. Nail in each corner, pierce corners of a second card to make a roof. The usual NMN floor. Add any internal detail and paint bottom half. Roof, if you want it removable plastic hair beads would work. Smaller nails or “V” folded card insert added to make an apex, suggest add coffee stirrer support to cover nails. Paint inside and bottom. Over this you add roof of cardboard, thin flock, tile, cardboard or papier mache. the one's below use one tongue depresser for a flat, strips of stretched scourer to make a thatched roof or simple one-piece scourer. Simple thick paint job and it's done. Finish off with more coffee stirrer bits if required.
If you want a stepped building, punch nails through bottom card then add a vinyl tile lower level(s). The depth of the nails will add a small step.
Remember, these go “boom!” or “whoosh!” if even glanced at by a Hero, so make some destroyed ones as well-.
Ran out of "A's, so battery is an "AA"
Sandbag sided tent. As above, but supports a little further in and a wall made by cutting scourers into 5mm strips and built up to 10mm height. You can go mad and cut into individual sandbags. Good coat of NMN. You could even add 6x15mm scourer beds.
Closed buildings, add walls of crinkled paper, stirrers or corn flakes packet card. Don't use silver foil, it discards paint. Makes lots of shanties. Consider a modular stable block.
Vehicle or building lean-to. Many parked military vehicles have the “makings” to put up a simple lean-to. I'm using bamboo skewers for the top. Yes, the uprights are too thick, but they do. Paint black with a smaller stripe to thin down. Building add-ons usually have pretty poor walls or roof.
Market place/larger tents. I've added nails of different heights then built up the roof and stalls with coffee stirrers. A little change and you can use same for bronze age to star colony. Remember that pursuits often bring these down, so make some collapsed path-blockers.
Smaller tents and soldiers lean-to's can be made using cardboard formers and match, pin or nail supports bedded in a punched hole and NMN floor. Using the card bases you can get some uniformity.
The type of thin packaging foam you find in chocolates and fragile stuff makes a fantastic roof, as it droops. paints well.