Is laying 2cm fine porcelain tiles possible or is it construction negligence?

Hello,

my new terrace is supposed to be covered with new 2 cm porcelain stoneware tiles for outdoor use. The terrace is not covered. Now I actually wanted to lay it loosely on gravel, but the landscaper said NO, instead he suggests the following:

[*] The terrace should be raised, therefore: [*] Remove old slabs and create and compact a new frost protection layer [*] Lay a new concrete slab with a slope then lay the tiles using the buttering-floating method with flexible mortar. [*] Then seal the joints.

Does that even make sense? What about the water? Is there not missing a drainage or a drainage mat?

Thank you very much in advance!

What is the concrete slab supposed to be good for besides filling the craftsman's cash register?

the structure is:
Unbound base layer (frost protection layer)
Bound bedding (drainage concrete)
Adhesive bridge (tile adhesive)
Ceramic tile (2cm in your case)
Bound joint (drainable)

as an alternative to the bound bedding including adhesive bridge, gravel, but this has not been the "state of the art" since the amendment of a norm unknown to me.

Ok. Thanks. Question about that:


what I could see, they produced the concrete on site with sand, decorative gravel, cement, and water. Could this perhaps be that drainage concrete?

And regarding the joint: why actually drainage-capable? There are also water-impermeable/waterproof joints. Wouldn't that be better? That way no water would get in at all, right?
The tiles are frost-resistant!


Thank you very much in advance!

As a rule, hardly anyone constructs their terrace with a true 2% slope away from the house. Therefore, it is better to let the water seep through the joints and the substructure rather than risk frost damage in winter from freezing water. If the ceramic is frost-resistant, that only means it does not absorb water that could cause it to crack when freezing. However, if water collects on your waterproof joint and freezes, it expands and causes chipping at the edges of the ceramic tiles. The joints wear out due to stress and eventually are no longer flush with the ceramic but subside by 1-2 mm. That is enough, and after a few winters, problems start.

Ok thanks. And regarding the concrete slab:

So, apparently cement, sand, and decorative gravel were used and mixed with water. And is it drainage concrete or not?

Here's how it looks:

Drainage concrete is available as bagged goods or in the composition you described as single-aggregate homemade mix. The term "floor slab" seemed a bit odd to me. "Drainage bedding" or "in drainage concrete" are common terms for this type of substructure. To me, it looks a bit too wet on the picture. But that can be misleading. I know it to be somewhat coarser in appearance. However, that doesn't necessarily mean anything. Was it a specialized company that has been doing this regularly and for a long time? If yes, then I wouldn't worry about it.