Press L — the toolbar calls it Ceiling (flat / open to roof) — then click the corners of the zone that gets a flat ceiling and press Enter, or click back on the first point, to close it. Rooms you leave outside the zone stay open to the roof slope above them. That is the whole idea: the zone is where the ceiling is, and the vaulted space is what is left.
A ceiling only makes sense under a roof, so draw the roof first.
The two fields
- Height — the ceiling’s underside above this storey’s floor.
- Thickness — the construction above it, which is what the storey above stands on in the 3D view.
The edges decide what closes
Where the edge of a ceiling zone crosses open space under the roof, a wall is generated to close the gap — otherwise you would look over the top of the flat ceiling into the vaulted room next door. Each edge can be held open instead after placing:
- A closed edge builds a wall from the ceiling up to the roof underside, wherever no real wall runs there already.
- An open edge leaves the flat-ceilinged zone connected to the vaulted space above the wall line.
Where you drew a real wall on the boundary, nothing is generated — the wall you drew is the closure.
Near the eaves
Where the roof slope dips below the ceiling height — which it does close to the eaves — the flat ceiling stops at the slope rather than poking through the roof. If you want it to run flat all the way to the wall, raise the roof’s Wall plate height. That is a raised heel in real construction, and the roof’s side closing follows the wall tops automatically.
What this doesn’t do
- A ceiling is flat. There is no sloped or coffered ceiling object; a vaulted room is one you leave outside a zone, not one you draw.
- One height per zone. Two rooms at different ceiling heights are two zones.
- It is not a room. Ceilings never appear in the room schedule or the net floor area — see rooms and areas for what does.
Next
Roofs for the form above it, and the 3D view to check the vaulted space reads the way you meant.