Renovating existing buildings: always exciting

Since I don't want to overuse the house pictures thread, but have come across quite a few projects in the forum where members are obviously also dealing with old buildings, gradually renovating them, and repeatedly discovering things worth preserving, I want to start this thread. Many of us often struggle with similar problems: damp basements, strange floor plans, thick-bed mortar, legacy issues—problems that don't usually occur in a "normal" house build. I would find it nice if we could exchange ideas here. How did you solve such problems, were there unpleasant surprises, what would you do differently today? Feel free to include before-and-after pictures as well.

So I'll just start, whether for edification or deterrence.

Here is one of our "small projects," the cube. The room is called that because it is almost exactly 3x3x3m in size. The problem: the outer corner of this room seems, for whatever reason, to be the coldest, meaning dampest, corner of the house. Consequently, the clay plaster had come loose there, some previous owner patched the missing plaster with cement mortar and thus created a perfect mold habitat. Despite regular airing, the moisture always remained there and then mold grew.

The first, probably somewhat naive plan was to remove the concrete, patch it with Klimasan renovation plaster, and that would be that. Fortunately, we then consulted a friendly clay builder who said: you’ll have to expose the entire wall, and the one opposite won’t hold much longer either. That was obviously not what we wanted to hear, but then I exposed the wall and the opposite one in a Hennecke layer.

And then the two stuffed-up windows appeared. The man was not at all thrilled and wanted to plaster over the mess right away, but a call to the carpenter sealed the deal: he was already making windows anyway, so he could just build one for us. So we made a lot of dirt again, carried debris bucket by bucket through the window into the container again, and ended up with severe muscle soreness again. But then the clay builder took over, and at least in terms of the cube matter, we could put our feet up for a while.

Just two brief details about the work of the clay builder: I could never have done it that well

After we had recovered mentally, physically, and morally from the clay orgy, we continued with the floor; the construction phase "sandbox" was initiated (the dog loved to dig here). The beams were hardly salvageable, more radical measures were necessary. And that meant shoveling again and carrying it out the window with buckets; we excavated about 30 cm. A test drilling up to one meter deep showed that underneath there was neither a secret cellar nor the Amber Room, but only "historic" construction debris, so we left it at that.

The door fitting is really nice