Fachwerkhaus under renovation
As you can see, this old timbered house is in desperate need of some renovation. And there's actually something going on inside (heard it when I walked by). My guess is that they knocked off the plaster to check the condition of the wood. With old houses there are often problems with decay or wood worms. It seems to be ok here.
Also you can see how the walls were built in former times - creating some sort of a grid with branches between the frames, fill it with straw, and then cover it with clay.
Renovating these old houses is very expensive because most of the times they are listed buildings, meaning they are under monumental protection. There are certain restrictions to what you can and cannot do and everything has to be as true to the original as possible.