Detached garage as roof terrace construction + covering with WPC

Hello everyone, I have a prefabricated garage (south side) made of 2 single garages with a middle wall opening. The dimensions are approximately 6m x 6m. I am currently considering how to best construct the surface covering. I was thinking of WPC. Problem: each individual garage has a parapet about 12cm high. That means in the middle there is a parapet from 2 garages (about 25cm wide and 12cm high). Question: How is it best to lay WPC through the parapet in the middle? I am afraid that if I lay the WPC above the parapet, how do I handle the edge? The garage was sealed with Aquamat (similar to Aquafin). The manufacturer recommends placing pond liner on top of it. How did you do it? THANKS for your answer.

If by "pond liner" you don’t mean PVC but EPDM (rubber), then you are correct.

Why don’t you simply make a substructure with wooden beams of appropriate height?

Place the beams on protective mats that distribute the forces over a large area and thus protect the rubber.

At the edges, you can let the decking boards protrude a tiny bit and then neatly define them with angle finishing profiles (there are also ones made of WPC).

Thank you for the reply. I plan to put a drainage profile/parapet profile on the attica at the edge. Now, if I raise the floor that high, it will even be higher than the profile at the edge. How should I raise the drainage edge at the edge?

Integrate the center strip into the construction as part of the floor. Then you have 2 WPC areas that are flush with the drip edge. We had a two-part Juwel double garage that from above looks like yours in the photo. With this type, I would have concerns whether terrace use wouldn't eventually overload the statics. Parties, jumping, and dancing are definitely prohibited!

Integrate the center girder into the construction as part of the floor. Then you have 2 WPC areas that are flush with the drip edge.
We had a two-part Juwel double garage that looks like yours from above in the photo. For this type, I would have concerns whether terrace usage would eventually overload the structural stability. Parties, jumping and dancing definitely forbidden!

Thanks for your suggestion as well as the warning.
Structural stability: I specifically have a version with increased load. Now the terrace reaches 7.5kN/m2.
Approval: here also it would be approved (costs extra 2000€ with the general contractor).

I fear that the center girder might be somewhat unpleasant to walk on. It is not even and underneath there is only a plastic profile.

One idea would be to build OSB on the parapet (at the edge) to raise the parapet.