ᐅ Steel beam in concrete ceiling – how to plaster around it?

In our living room, there are two steel beams between the concrete ceiling slabs.
My plasterer doesn’t consider the gap between the individual concrete slabs to be a problem and can fill it.

However, he sees an issue beneath the steel beams. If he were to fill it there, it would only hold for a short time.

Has anyone in this forum dealt with a similar situation?
What would be the simplest solution here?

How about using simple battens and then covering them with drywall?

We also have a steel beam in the living room, which will be plastered in about 2 weeks. Our site manager said that a kind of mesh will be applied first, otherwise the plaster wouldn't adhere. I'm curious to see how it will be done.

Best regards
Sabine

Using battens won’t work here. The recess is about 1.5 - 2cm (0.6 - 0.8 inches).

The problem with this "mesh," probably plaster reinforcement fabric, is how to fix it in place. Attaching it under the concrete ceiling is difficult. It would protrude from the ceiling, ruining the smooth, flat surface...

Curly schrieb:
Our site manager said that some kind of mesh will be applied first, otherwise the plaster wouldn’t adhere. I’m curious to see how it will be done.

I assume the mesh will be fixed with mortar or construction adhesive (not fully covered, so the plaster can also bond behind it). But the plasterer should actually know the details better, and it should be routine for them, so I wonder what kind of training they have. Seeing that they consider this a problem suggests to me that they are only semi-skilled (even though it’s typically a formal trade, but nowadays apparently one without a mandatory master craftsman qualification).

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To explain it more precisely:
Our ceiling will NOT be plastered. It will also not be dropped with drywall, as the recessed spotlights are already planned to be installed in the concrete ceiling.
So unfortunately, applying a mesh on the concrete ceiling is not an option.