Well, with prefabricated houses, it is not uncommon to have the foundation slab or the basement constructed separately.
Secondly, exploiting the inexperience of a construction layman by a construction professional does not become better by the fact that unfortunately it is not uncommon, and first of all, this practice comes from a time when prefabricated houses were still mostly built on basements. In the case of a full basement under a one-and-a-half-story house, one could still argue that it should be regarded as a separate component. A simple beer coaster, on the other hand, in my opinion, is merely an ancillary service to the delivery of an entire house. No one would accept being referred to parts trading to get the indispensable exterior mirrors and bumpers when buying a new car – even if just a Dacia. Therefore, in the case of a house with a foundation slab, this is simply shameless exploitation of laymen, shirking responsibility for this highly fit-critical interface with the false argument that back when prefabricated houses were built on basements, they were only offered starting from the finished floor level (OKKD). In the past, we had a Kaiser – back then, the Ergo Group was still called Hamburg-Mannheimer *LOL* Today, houses with a foundation slab are rather the standard, and those damned exterior mirrors must be included, period. Anything else is unprofessional. Even lawyers know this phenomenon of changing customs – as so-called life realities. Offering a house without a "K" still as "from OKKD" is "out of touch with reality," far from the market reality – even if competitors consider their customers just as naive. Here, it is a matter of plain "unwillingness to admit non-existence" when the fist later does not match the eye. The "consumer" builder should not let these scoundrels get away with it!