ᐅ Roof Terrace on a Flat Roof – Construction – Surface Covering

Hello everyone,

We have a sloped plot of land, so our garage has a flat roof that will later become a terrace. The terrace is accessible from the living room and is approximately 40 sqm (430 sq ft).

The garage is masonry with concrete ceilings. Bitumen sheets were installed and welded on top, then a slope was created using Styrodur (I think), and the "roof" was finished with welded flat roof membrane.

Now we are wondering what to put on top of this membrane. Unfortunately, we have quite a low build-up height—10 cm (4 inches) below the terrace doors and at one corner even only about 5 cm (2 inches) because of the slope.

Wood/WPC
At first, we considered wood with the appropriate substructure, but I suspect that would be too tall.. :-/ Also, we should not forget the effort required for annual oiling.
We do not like WPC at all; to me, it looks way too "plastic-like" over such a large area. On a smaller terrace, I could imagine it, but not on our large one.

Stone/Ceramic
We were advised to use paving slabs on a gravel bed for the terrace. Specifically, these new "ceramic slabs," which are only 2 cm (¾ inch) thick but suitable for outdoor use. They are simply laid loose on the gravel and held in place by their own weight. However, they are quite expensive—over 50 EUR/sqm (about 5 USD/sq ft). What other affordable stones/slabs/tiles are available?

Questions
What other options are there?
Which of the mentioned options offers the best value for money?
Who already has experience with these ceramic slabs and can share their feedback?

WildThing schrieb:

It is a masonry garage with concrete ceilings. Bitumen membranes were installed and welded on top, then a slope was created using Styrodur (I believe), and finally the "roof" was made with welded flat roof membrane.

Was the garage or its roof applied for as a terrace?

Best regards, Bauexperte

Yes, this was applied for from the beginning, included in the plans, and structurally engineered.
(The garage is also not located on the property boundary)

Thank you!

I asked because the construction of the flat roof seems a bit unusual to me, especially since it was known and still is that an additional covering will be applied.

Best regards, Bauexperte

Really? Why? How is it usually done? Only the overall height turned out unfortunately. We had specified 10cm (5 inches), but the flat roof contractor apparently calculated it from the patio door instead of the highest point of the insulation.

All good – I simply missed the concrete ceiling. Sorry for the confusion.

Best regards, Bauexperte
Bauexperte