Idk the English word for it, but there is a kind of foil that is water resistant and where roots cant go through, as long as its not a tree or something at least. Its put between the foundation and the walls to stop water from below.

Pond liner is just what the translator got out, its probably incorrect.

Also im talking about this

Not planting literal trees on balconys, that would be a structural problem, yes. But small shrubs and Twiners would do the trick as well if not better in regards of cooling and weight. They also don't need much soil or and significantly less water.

Also can you stop spamming emojis?