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.
What the ceiling belongs to
The Ceiling is row is the first decision:
- Independent — a ceiling of its own at the Height you give it, measured from this storey’s floor.
- <Storey> floor — a lining under the floor of the storey above. It hangs flush under that floor and takes its shape, so the two read as one build-up; its own outline and height go unused while it does.
- Roof N — the roof’s own finished underside, given a thickness and a build-up. It adds no second surface, so it does not appear in a section as a plate of its own.
Attaching is what stops a ceiling drawn under an upper floor standing as a second mass below the slab. A lining whose host is deleted is kept and reported by the plan check as A ceiling lining has lost what it hung on, never silently detached.
The other fields
- Height — the ceiling’s underside above this storey’s floor. Replaced by a note once the ceiling is a lining.
- Thickness — the construction above it, which is what the storey above stands on in the 3D view.
- Build-up — a named construction, which sets the thickness with it.
- Thermal — Automatic, Part of the envelope or Inside the building for the heat-loss sheet. A lining has no role of its own; a ceiling under another storey is internal.
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.
- A lining never caps a wall. Attach a ceiling and it is a finish on its host, not a lid: the walls under it are raised by the same rules as before.
Next
Roofs for the form above it, and the 3D view to check the vaulted space reads the way you meant.