Terrace construction over an unheated garage

Hello everyone,

in the meantime, we have had several craftsmen on site and unfortunately still do not have a satisfactory solution. Unfortunately, we only have a build-up height of 15cm ([Rohbaudecke bis zur Hebeschiebetür]). It is made more difficult by the fact that I am in a wheelchair and the transition from the lift-and-slide door to the terrace must be barrier-free. The garage under the terrace is not heated. We want to prevent condensation from forming on the ceiling in the garage and ensure that the terrace is properly drained. As flooring, we were thinking of terrace slabs with a thickness of 2cm.

I have created the following sketch for this.

We would be very grateful for ideas.

Quite simple and easy (static) would be to place wood or WPC on pedestals. Since there is a frame, damaging the roof membrane is unnecessary. The pedestals are height-adjustable, making the slope for water drainage under the horizontal terrace straightforward.

This is how it looks with untreated larch after almost 6 years with us.

This is how our WPC decking boards with seals look like, as barefoot decking after 5 years

Thank you for your feedback.
Thanks to you as well, drainage was not relevant in your case.

- Would wood/WPC have an advantage over terrace slabs 120x60 in 2cm thickness?

- My main problem is how to realize the slope. One craftsman says there must be insulation on the garage, the other says there must be no insulation on it.

I would work without insulation using pedestals, with which you can adjust the slope and compensate for unevenness

I understand you to mean that the tiles then have a slope, but doesn't the water then run down through the joints? Would I even need a sloped screed there at all?