Concrete - How to seal columns on the balcony?

Hello dear forum,

we have 2 balcony columns where the plaster does not hold in the lower area. The assumption is that moisture is rising from below. Each of them stands on a foundation and at the moment they are not sealed at all and stand about 50cm deep in gravel. How would you seal something like this? Or do you see another reason for the plaster flaking off?

What kind of concrete was used?

I would excavate as deep as possible and coat with bitumen, plaster the rest with a base plaster.

Type of concrete I unfortunately do not know, it is also not stated in the documents. The supports were poured on the construction site.

As you write, we also thought the same, dig out and bituminous coating. Since the gardener is coming the week after next, he can do it at the same time.

Thank you

The columns are supposed to be plastered, right?

If you coat the concrete columns with bitumen sealing compound, you only protect the columns with it, and the plaster on top will effloresce and flake off in the same way. You urgently need to do a base sealing there.