Quick set

All floors

Set thickness for all walls. Changes apply on 3D rebuild.

Go to the floor you want the open shaft to start on, then define the void. Set its From / To floors in the list — the slabs of every floor above From, up to and including To, are cut, so that room rises multiple storeys. Walls stay as drawn — only an interior partition left floating inside the opening is hidden.

Select an enclosed loop of walls (Edit or 3D view) then From selected walls, or draw the outline directly. Click a void in the list to select it — the Edit viewport focuses it and its outline becomes an editable polygon (drag handles, click an edge to add a point, double-click a handle to remove it).

Voids

Roof caps

For a small roofed structure (mumty, lift-machine room, tank enclosure) on an open level: draw its walls, set their height, select the enclosed loop, then Roof over selection. A flat roof slab is placed at the walls' top — the rest of the level stays open.

Calibrate by entering a known door width, or select a wall in Edit tab and enter its real length.

Know your building's real footprint (e.g. a 100,000 sq ft shed)? Set it here — the whole plan is scaled so the outer wall footprint matches it exactly, overriding the calibration above.