ᐅ Which type of plaster should be used? What are the differences?

Hello.
Soon the plasterers will arrive at our new build.
Since we want to have only a small amount of wallpaper and tiles on the walls, we have now chosen gypsum plaster from the options offered by our builder (cement plaster and gypsum plaster). Due to its smoother surface, it should be better suited for our project. According to the builder, the entire house can only be treated with one type of plaster. So it is not possible to switch to cement plaster in the bathrooms.

My question is:
Is gypsum plaster always the same as lime gypsum plaster? If not, what are the differences between lime gypsum plaster and gypsum plaster? Is the only difference the mold-inhibiting effect of lime?

Additionally, it is important to us that no moisture can penetrate through the plaster. Is this true for all types of plaster? Cement plaster absorbs moisture to some extent and releases it again. Wouldn’t that mean that moisture also passes through the plaster? This concerns the stone wool insulation behind the plaster. In some areas, moisture protection is only ensured by the combination of plaster and vapor barrier. Or would you recommend a completely different plaster? What do you think about using gypsum plaster in the bathroom? A controlled ventilation system with heat recovery is in place.

A bathroom is not considered a wet room (as long as there is no pool or sauna), so gypsum plaster is allowed there.
To ensure it can absorb moisture, you should not use simple paint (if it is not tiled); prime the surface first and then use a silicate dispersion paint (vapor-permeable).

Rock wool directly behind the plaster? Without drywall? Where is that supposed to be?

All right. Is gypsum plaster always gypsum-lime plaster?
Of course, we have just completed the drywall.
Some cables and empty conduits, for example, run over the knee wall to the membrane. The transition there always had to be chased out.
In my assessment, the membrane is no longer completely sealed in some places. In some areas, three empty conduits 40x40mm (1.6x1.6 inches) run side by side into or against the membrane.

Tx-25 schrieb:

According to the developer, the entire house can only be finished with one type of plaster. So, switching to cement plaster in the bathrooms is not possible.

This statement is based on calculations or organizational reasons. Technically, it is not a problem.

Tx-25 schrieb:

Is gypsum plaster automatically always lime gypsum plaster? If not, what are the differences between lime gypsum plaster and gypsum plaster? Is it only the mold-inhibiting effect of the lime?

Tx-25 schrieb:

Is gypsum plaster automatically always lime gypsum plaster?

No, gypsum plaster without lime additives is less expensive.

Tx-25 schrieb:

If not, what are the differences between lime gypsum plaster and gypsum plaster? Is it only the mold-inhibiting effect of the lime?

The main difference is the mold-inhibiting property.

Lime plaster is also available with a cement base, which would be better suited for a bathroom because cement does not tend to swell. In a private home bathroom, I would have no concerns using simple gypsum plaster, since it is not a permanently damp room. Additionally, there are sealants that prevent water absorption and can be applied locally.

We chose clay plaster, which is also said to reduce harmful substances and neutralize odors very effectively. The material is somewhat more expensive, but the cost can be easily offset by not needing the often costly smooth finish required for skim coat walls.

Thank you for the feedback. How does it work with moisture passage? We put a lot of effort into making the vapor barrier airtight. Unfortunately, the electrician made a bit of a mess afterward. As I understand it now, is the sealing mainly achieved by the final paint? Or is the plaster itself already airtight?

Tx-25 schrieb:

Or is the plaster itself already waterproof?

Sealing the plaster surface is rather unfortunate, as it means losing the unique properties of this building material.