Substructure for terrace

Then you could also remove the gravel, put some crushed stone on it, compact it again and put some more gravel on top. I would also find it pointless to do it completely new, at least based on the information we have.

That's exactly how the landscaper wants to do it.

yes, ok. But why is it allowed to be max 50mm? What happens if it is more? Sorry, I just want to understand

Splitt are basically "large" stones, which give little way downwards, but can be relatively easily displaced sideways. The thicker the layer, the easier the fun can slip sideways. If the slabs are enclosed all around in all 4 directions with concrete, one can certainly do it something like that. As I already said on page 1: either take slabs of the same height, consider whether 2cm lower is a problem, or do it properly and take up the fun, underpin it, and put Splitt back on top.

The other way around. Splitt is the finer material... Schotter, on the other hand, are the larger stones that Payday is talking about.