Plaster the underside of the carport

So both systems mentioned here are good and should solve the problem.

I would need a construction sketch so that I can understand it better

We built a wooden carport and had it plastered so that it looks like masonry from the outside, matches the house, and is protected from the weather. However, underneath we left the wood exposed because it is simply super practical for quickly hanging or attaching something. And we also like the look. But well, a matter of taste.

As a plaster carrier board, we used simple 1000x500x30mm Styrofoam boards from the hardware store and glued them to the OSB boards with mounting adhesive. On top of that, the plasterer then applied his mesh / base coat and then the top coat. I can’t say whether this works fully upside down, as for us it was only the walls. But it has been holding without any problems for 1.5 years now.

Could you tell me how you ultimately did it? Thanks to you

Nothing has happened yet. But it will be a wooden underside. The risk of cracking was ultimately too high for me. Since neither my BU nor the carpenter have ever done this before, I did not want to be a test subject.

It is a masonry carport that is integrated into the house.
That is why the same appearance should be created everywhere.

Was the front view/the canopy of your garage built of masonry/concrete? Or how is it clad?