ᐅ Mineral-based exterior plaster, painted once or twice

Hello everyone,

We are about to have the exterior plaster applied (thermal insulation composite system using rigid foam insulation boards). It is a mineral-based finish coat with a 3mm (1/8 inch) grain size. According to the building specification, it will be painted once with white paint (standard service).

However, the contractor recommends applying two coats for an additional cost due to
- longer durability
- extended effectiveness of the fungicide in the paint

This is especially important because of the insulation system, as the plaster is more susceptible to moisture due to the polystyrene cladding.

What are your thoughts on this? How many coats were applied in your projects?
Thanks in advance for your feedback and opinions.

I am not aware of any white exterior plaster being painted in our new development area. This concerns about 70 houses.

We had the leveling coat applied. The additional cost was minimal.

EveundGerd schrieb:
We had the leveling coat applied. The additional cost was minimal.

This makes sense if the exterior plaster is going to be colored; the leveling coat prevents—simply put—an uneven facade.

I assume that the painter for the original poster recommended a second coat solely to sell a fungicidal and algicidal treatment. It should be noted, however, that these additives—whether chemically or ecologically safe—wash out over the years due to rain.

What I don’t quite understand is why a mineral-based exterior plaster would be applied over an external thermal insulation composite system (ETICS). From a durability perspective, in my opinion, a synthetic resin-based plaster would be a better choice.

Regards, Bauexperte

Even better would be a mineral fine scratch render, so you wouldn’t need to apply chemicals or repaint it.

Thank you for the contributions, except for the first one.