ᐅ Should you use lime-cement plaster or gypsum plaster for interior walls?

I always cook potatoes with the lid on the pot. The amount of steam escaping through the vent hole is minimal. The similarity between this and taking a shower is about as much as between a broomstick and a bus.

Except for reducing sauces or something similar, nothing in a kitchen should generate steam levels comparable in any way to what happens in bathrooms. The idea of a “wet room” and swelling gypsum plaster is nonsense.

The same goes for indoor climate. No wall can do what a few nice plants can—just decorate with a few large pothos (also called devil’s ivy), and that’s all you need for a good indoor climate. The type of plaster doesn’t matter.

I’ll just say

Due to its versatility and advantages in use and application, gypsum plaster is commonly used in both residential and non-residential buildings. Specifically, it is suitable for all types of interior spaces, including domestic kitchens and bathrooms. These are not considered wet rooms but are classified, according to DIN V 18550 Plasters and Plastering Systems – Execution, as rooms with “normal indoor humidity,” because moisture exposure to walls and ceilings there is only temporary and mainly due to splashing water. When the room is used as intended, gypsum plaster surfaces may get wet occasionally but can dry out again without damage to the plaster.

The situation is very different in true wet rooms, such as commercial kitchens, swimming pools, or public showers. Long-lasting moisture exposure to surfaces can occur here, so gypsum plaster should not be used. In environments with constant water exposure, the crystal structure of gypsum loses strength. This distinction between (commercial or public) wet rooms and domestic kitchens and bathrooms is made in both the aforementioned DIN V 18550 and a number of technical leaflets, such as the leaflet on bonded waterproofing systems.

If you prefer cement-lime plaster, that’s fine.

But I know from our interior shower bathroom that even after almost 20 years, the gypsum plaster is still in the same condition as when it was applied.

Exactly. Bathrooms are only called wet rooms colloquially.
With 2 liters of steaming cooking water in the kitchen, I wouldn’t worry either. Compared to a shower and considering the size difference of the rooms, I find that irrelevant.

A rain shower uses over 20 liters (5 gallons) at full force. Honestly, a terrible trend.

I currently have two quotes for interior plaster. The surcharge for switching from gypsum to lime-cement plaster per square meter is €4 (about $4.30) in one offer and €1.70 (about $1.80) net in the other.
However, the specification includes twelve times more area with gypsum plaster.

What a fuss over nothing. Could have, would have, should have. Some people only use their kitchen as decoration anyway, while in other households, a family of five cooks twice a day, 365 days a year. But that doesn’t really matter. An open kitchen can cause temporarily increased humidity, which may cause issues at thermal bridges elsewhere in the house. Gypsum plaster is more sensitive to moisture than lime-cement plaster, so what’s the point of this discussion? That doesn’t mean everyone’s gypsum plaster will start to swell overnight; no one claimed that.

Gypsum plaster is cheaper, easier to work with, and (a matter of taste) looks better. If the mover bumps into a bulky floor lamp, gypsum plaster is more likely to be damaged, and a scratch is more noticeable on its smooth surface compared to the typically rougher lime-cement plaster. That should not be forgotten either.

This is similar to the argument of someone who has had concrete tiles on the roof for 50 years and is still very satisfied, while their neighbor had to replace clay tiles after just 40 years.

In our area, for example, cold cement plaster is used as the base coat for masonry houses in about 95% of cases. The finishing coat with the desired grain size, for example 0.8mm/1mm/1.5mm/2mm (0.03"/0.04"/0.06"/0.08") is then applied on top (dash coat). The plaster is rarely applied smooth... which is probably more common for timber houses... where they simply fill, paint, and done.
I have lime-cement plaster in the bathrooms, and pure lime plaster with a pure mineral-based finishing coat in all other rooms.