Step from the living room to the terrace?

Does that have to be done too?

If there is no step, then yes. The regular patio door is also nearly flush with the floor. Just google "drainage channel patio door." There is also a DIN standard for that.

To "fill" onto the concrete slab, use so-called Einkorn concrete. On top of that, gravel and then the terrace slabs. In front of the doors, as written, a drainage channel. It does not necessarily have to be connected to the drainage. It has slots and thus directs the water into the gravel layer.

If it does not exit flush with the ground, it might even work without a channel.

P.S.: I find the Kann Fiori very good. We have it too. But it is a matter of taste.

We have been living with [Stufe] for over 20 years and also have it in the new house. It doesn’t bother me or my family at all. The very old ones sometimes sigh…

clearly without a step! I always find these a big tripping hazard, especially when you're holding a tray in your hand...

At the "main exits" to the terrace, we also placed value on a floor-level threshold. After all, you usually go in and out there more often than through the front door. And they are always without a step :)

Ok so you pretty much agree that we should do it without a step. Then we’ve already clarified that... you’ve convinced us. I’m also used to having a step at home. That’s why we considered it. Also because of rain and snow. The thing with the front door is also a good argument.

Is concrete better than graveling under the crushed stone?

I’ve already seen many people who did the terrace without a drain. One said they have a slope on the terrace. But you would strongly recommend a drain, right?

And then the outer slabs in concrete, so that it holds because of the raised gravel bed (or leveling with the special concrete as suggested). I read that there is a drainable concrete, which you should probably use for the outer slabs, right?

Thanks again for all the answers!

I know this doesn’t really fit my headline. But maybe one of you happens to have a Weishaupt Biblock heat pump. Since we’re doing the garden at the moment, that’s related to our topic right now. The heat pump releases so much water that we had extreme problems in winter and we still have to solve that. As prescribed by Weishaupt, we have a big hole with large gravel under the pump for drainage. But it doesn’t help.