How to handle natural stone slabs for a terrace?

Our garden and landscape gardener said that the fine gravel wedges itself into the joints, reduces rocking, and only then gives stability to the surface. And brush off nicely, about 3-5 times, at intervals of 4 weeks

The same sand or always new? I have to admit, since the slabs lie against each other, nothing actually gets through there.

If there are no joints at all, then from my layman's perspective, that's already sloppy. The gravel gives the slabs stability. Due to rain and small movements, the gravel shifts in the joints, so it has to be refilled regularly in the first few weeks.

My neighbor told me that in his company, they only lay terrace slabs on gravel with a written exclusion of corrective work for settlements. Because according to him, these occur almost always, sometimes earlier, sometimes later.

The same sand or always new?

The landscaper had left 2 buckets full of fine gravel, and I swept sporadically afterward; there were always some joints that had settled again.

With us, there are definitely 10 slabs, if not more, that have sunk. A friend who also does a lot of this kind of work said that with the number of sunken slabs and because they are always laid directly next to each other without joints or anything similar, the terrace builder would have to remove, level, and relay almost 75% completely. He also said that quartz sand is crap, you leave a minimal joint and sweep in resin, which then hardens over the years.

What do I do if the terrace builder says that this is the case with natural stone, nothing can be done? Or what if he does not want to remove all the slabs, but only those that have sunk, which due to the tight laying cannot be removed and therefore he has to break them to insert new slabs?

What do I do if the terrace builder says that this is the case with natural stone, nothing can be done?

Then he wouldn't be entirely wrong, but this is not due to the natural stone itself, rather to the method of installation. Even after rework, you will experience settling again. Alternatives would be, for example, pedestal supports, but of course that costs more. Or even better, single-grain/drainage concrete. However, for that it is too late for you without complete dismantling. The main problem, however, is the lack of joints, as the slabs cannot support each other that way.

We knew that and he had also said it, always with the addendum, we can fix it later. But I wouldn't have thought there would be so many tiles. In addition, I have been told that Kalkspitt was also the wrong choice for him, as it decomposes at some point. All in all, very disappointing for just under 14k€.