As a 'rule of thumb' I divide the stories up with the 1.500 mm floorplan plane projection in mind. If the split level gap is close to or more than 1.500 mm, I would create a seperate story for it. If it is more like a 1.000 mm or smaller difference, I would set up a 2nd set of view with adjusted floorplan cutplan (for example 2.500 mm).
There tends to be a certain amount of masking of unwanted elements etc with the small story differences, but it is possible to make it work.
Also keep in mind the behaviour of things like stairs with story up and story down symbol. Doors and windows are also notoriously fiddly with 2d symbols.
Things like wall projection play a huge part in getting the floorplan to look like you would want.
Sometimes you have to divide walls up vertically per story to get the sort of behaviour you would like in floor plans.
Erwin Edel, Project Lead, Leloup Architecten
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