Thank you @kurt.battisti for mentioning the cases.
Personally, I see some discrepancies that I would like to comment:
- I don’t believe the position of the SSL of a load bearing slab is defined (in the design phase) before knowing where the FFL is. In many cases the designers work with a structural slab and finishing one as a whole, since it is not very clear in the beginning what are the exact thicknesses of the finishing layers (fire safety, acoustics, loads, etc.) and also the structural engineer comes first with a suggestion before doing a more precise calculation. In addition, there are also parameters that define the total thickness of the structural slab, meaning how is going to be built: reinforced concrete, steel construction, Cobiax, precast.
- True, most of the vertical elements sit on the structural slab.
- When a slab is being built in reinforced concrete, in many cases we are dealing with the lowering of the slab while drying. That is why the designer must plan the so called “the sliding connection” for walls, in order to avoid compression forces on those walls that would create unwanted cracks. Meaning the lower part of the raw ceiling is horizontal only in the virtual model, but not in reality. That is why all these discrepancies are leveled with the finishing layers that come above the structural slab an to achieve an almost ideal horizontal level of the finishing material. Tolerances in structural construction (Concrete) are in CM, whereas for the finishing layers are in MM.
- True, the raw construction is one of the first to be seen on the construction site. But as I mentioned previously, the tolerances are 2-5cm. Talk about precision
