Here is a WIP picture. You can see the main body is a plastic construction with the glued on wooden parts. The roof planks were made from balsa wood at first but I wasn't satisfied with the result and made them from coffee sticks instead.
This one isn't finished obviously. The tiled roof is made from textured plastic card from the architectural supplies store.
The two storey houses are not made from plastic like the two smaller ones. I stumbled across this wooden boxes in a 1€ store. I knew immediately that they were perfect for this project and bought all of them. The roofs are still made of plastic.
BTW: Big shout out to Jimbibbly's blog. His work is a true inspiration.