Levels and stairs
A level is a datum, not a floor. A stair joins two datums, and the hard checks are about what surrounds it.
A level is a height you are working at — a finished-floor elevation and a
floor-to-floor height. It is not a slab and it is not a storey of geometry.
Rooms, walls and roofs say which level they belong to, and that is how a
building gets its layers.
{"t":"level","id":"g","name":"Ground","elev":0,"height":3}
{"t":"level","id":"u","name":"Upper","elev":3,"height":2.8}Look at the second elev: it is the first level's elev + height. That is not
a convention you are invited to follow. Storeys must stack exactly, and a
gap or an overlap is level/stack, a blocking error.
It is the cheapest guarantee in the format. A building cannot have a floating storey, so nothing downstream ever has to wonder.
A mezzanine is not a second storey; it stays inside its host level and is
checked for it, by level/orphan-mezzanine and level/mezzanine-overruns —
both blocking.
Stairs
{"t":"stair","id":"stair","from":"g","to":"u","x":4,"y":2,"w":1,"run":4.2,"dir":"east"}
{"t":"void","id":"stair-void","level":"u","x":3.8,"y":1.8,"w":1.4,"d":4.6}The stair names two levels. Its rise is the difference between them — you never write it, so it cannot disagree with the storey heights.
The void is what puts the hole in the floor above. Leave it out and the stair
draws perfectly and arrives at a solid ceiling; stair/no-void is the warning
that says so, and it is the one people skip past.
The idea worth carrying away
A dimensionally perfect stair can still be wrong, and every interesting check here is about what surrounds it rather than the stair itself:
stair/through-wall | the flight passes through a partition — blocking |
stair/orphan | it names a level that is not there — blocking |
stair/no-landing | a run long enough to need one does not have one |
stair/no-void | it arrives under a solid slab |
None of those can be found by looking at the stair. They come from reading it against its two levels, the walls it crosses, the rooms it lands in and the void above — which is the kind of question a drawing set answers and a single drawing cannot.
What bites
level/no-entry is a warning that means the building cannot be entered. No
exterior door, stair or lift reaches that level from one with an entrance. It
reads like a small complaint. It is not.
A lift has to stop where it passes. lift/no-landing catches the shaft
that runs past a floor it is supposed to serve.