Roofs
Four shapes from one tool. Hip roofs work over any polygon, not just rectangles — the geometry comes from a straight skeleton, so an L-shaped or U-shaped plan gets correct hips, valleys and ridges.
Draw one
Section titled “Draw one”| Roof on the toolbar | rectangle, two clicks |
| Polygon — ← / → in the Roof tool | click the corners, double-click to finish |
| Roof from Walls — select walls, right-click | outline from the outer face of a closed ring of walls |
Roof from Walls takes the outer face at the top of the walls; the overhangs are added by the roof itself, exactly as for a drawn one. A hip or gable roof then asks for its gable edges the same way a drawn polygon does.
Roofs are drawn on the top of the walls of the active storey, not on whatever the cursor happens to hover over.
Shapes
Section titled “Shapes”| Flat | any polygon |
| Shed | single slope, any polygon |
| Gable | two slopes to a ridge |
| Hip | slopes on every side — any polygon |
For gable and hip on a polygon, after you close the outline the tool asks which edges are gables: hover an eave edge and click to toggle it between hip and gable. Chosen gables show in green with a live wireframe preview. Enter builds it, Esc goes back.
Some edges refuse — a gable needs a triangular plate to collapse, and where the ridge runs parallel to the edge there isn’t one. The tool beeps and says so.
Pitch, eaves and overhangs
Section titled “Pitch, eaves and overhangs”| Field | What it does |
|---|---|
| Pitch | slope, in degrees or as a ratio |
| Eave cut | how the rafter end is cut |
| Eave overhang | how far the roof runs past the wall |
| Gable overhang | how far it runs past the gable end |
Eave cut has three options: plumb (vertical face), square (perpendicular to the slope) and level (horizontal face). Each has a small preview in the dialog.
Composite shapes
Section titled “Composite shapes”Draw the pieces as rectangles and combine them:
| Merge | fuse two roofs into one object |
| Trim | cut one roof at another — click the side that should disappear |
| Extend | run a roof out to meet another, then cut it to the surface |
Click order is the same as for walls: first the roof that changes, then the one that acts as the reference.
Openings
Section titled “Openings”| Opening | draw a shape on the roof and cut a vertical penetration — a chimney or a duct |
| Skylight | a rooflight lying in the plane of the slope, with a frame and glazing |
| Del Open / Move Open / Copy Open | edit either kind |
Penetrations are cut vertically through every plate they cross. Skylights sit in the plane and can have their reveal either vertical (the manufacturer’s usual detail) or perpendicular to the slope.
A skylight can be positioned from the storey below — set placement to floor and the sill height is measured as a real vertical height above that floor, which is how the dimension normally arrives.
In IFC and in drawings
Section titled “In IFC and in drawings”Exports as IfcRoof with Qto_RoofBaseQuantities and Pset_RoofCommon.
Skylights export as IfcWindow with PredefinedType skylight.
In plans, a roof above the cut plane is drawn as a dash-double-dot outline of its top edges — eaves, ridges, hips and valleys — placed in the storey it belongs to.
Compositions on a roof are drawn per plate, with the layers perpendicular to each slope rather than to the ground.
See also
Section titled “See also”- Compositions
- Walls — To Roof for gable walls