Plaster falls down? Treat surface with tile adhesive first
Anyone who ever wanted to plaster a lintel or a concrete ceiling, will certainly have found a big problem: to bring a plastic mass in contrast to gravity to stop ;-)
The problem arises mainly through the use of formwork oil on the building formwork, which should prevent concrete from sticking to the wood. Unfortunately, this sticks to the concrete surfaces and then acts as a release agent.
To nevertheless achieve a positive result, first fill the surfaces to be plastered with tile adhesive and allow to dry.
The next day the plastering goes by itself.
If you use normal plaster, make sure that it has a fine sand grain (0-1mm) also called cleaning sand. The normal sand (0-2mm), known as masonry sand, is too coarse from the cavities and settles from the ceiling / lintel.
