Renovating vaulted cellar - experiences

The holes in the floor in front of the wall, is that a drain?

Renovation plaster would not be necessary, he said. He doesn't think much of that sealing spray stuff (can't remember the name). We did nothing at all. However, the basement room is not built over and is underground on 2 sides.

The holes there in the floor in front of the wall, is that a drain?

I suspect so. But I don't actually know. It's a good question.

There are different methods for basement waterproofing. And if you do it, you should really waterproof completely, otherwise you only cause new problems. But I wouldn’t do it.

I would clarify the issue with the possible drain. Where water comes in, it can also go out. Keyword: hydrostatic pressure during backflow. We also have a drain in the floor in the laundry room in the basement; after several heavy rains, water was pushed up a few centimeters there, and it drained away quickly again. But: if a pipe goes out there and it is not tight, and maybe there is also a (rain) water pipe running on the outside wall, that could be an indication of the damaged spot. All without guarantee, just a thought. If the neighboring house is there, also consider problems caused by the neighbor’s house.

On the subject of ventilation: continuous ventilation at -10°C will probably cause you more mold rather than less. The motto is shock ventilation, also in the basement. At transitional temperatures, you can ventilate longer; in summer and winter, it’s basically just shock ventilation. At least that’s my information, and that’s how I do it too.

So, here built in 1920, Prussian cap ceiling - even more critical due to the exposed steel beams, brick on the floor. The humidity fluctuates, but by now I have it under control. And that is already the keyword: from my point of view, it is unrealistic to want to fully control it through insulation. That only works if you create an envelope. That is practically impossible because moisture also comes from below. The moisture (depending on season and weather) was back then not only a bug but a feature, which for example favored the storage of fruit and vegetables. Under these conditions, in my opinion, only a reasonable ventilation concept helps, possibly with supporting heating. Two dew point-controlled fans diagonally with heat recovery, for example, combine both. At a fraction of the cost for more elaborate renovation - and with quite certain success. I cannot report firsthand because I ventilate manually. But the user reports show good results. (An exception is of course when water pushes from the slope, then something must be done from this direction as well).

You can also check if you can open opposite basement windows for cross-ventilation during shock ventilation. Regarding the rest, I share the same view as HausiKlausi.