Terrace construction over an unheated garage

unfortunately, there is no slope on the garage roof

What solution is there on the roof to drain the water? about the material: Wood or WPC has no fundamental advantage over tiles, except possibly the lower static load it causes. Many do not trust wood to have an adequate service life, which could be seen as a disadvantage.

Question again: Has the garage roof/flat roof not been sealed at all so far? How has the drainage of rainwater been managed so far?

Hello Arauki11, until now it was not sealed. We had made a hole in the wall where the water then flowed into a downpipe.

But a flat-roof garage would have to be sealed in some way anyway. In this respect, you could then add a screed with a slope underneath and place pedestals with any covering on the sealing (foil). Maybe you could post 1-2 pictures.

Is this a border garage?

If you have drilled a hole in the wall (Attika?) then presumably a slope leads there.

Pictures really help.