It's a foamboard shell covered in various textures of card (mainly corrugated) with some fairly solid packing card for the roof. The front door is from the GW Cities of Death kit (cut down yet still massive!) and the dilapidated couch out front is from Black Cat Bases. I-beam has been used in various points around the building as supports.
The rear shows a ladder to the roof (a Hexplatformer piece) and a roadsign (from a kids construction set I picked up for the vehicle).
Odds and ends from various sources have been used - the window on the side is from a Rhino kit, there is a random toy robotic claw and a claw from a "Kryptonite Capture" (or something along those lines) Superman toy covered in chained down tarps. The theme behind the shack was that it was home to a robotics engineer.
There's another roadsign on the other side, plus a component from a Leman Russ kit.
I've also taken some better pictures of the two shanties I completed earlier - I'll post about them in the near future.