A roof shape is the geometric form of the roof of a building, determined by the number and direction of the roof slopes, the pitch angle and any breaks or transitions. The roof shape strongly influences the appearance of the building, the usable loft area, water drainage and the structural build-up.
Main roof shapes
In British and European construction the following roof shapes are most common:
- Flat roof — nearly horizontal surface with minimum fall for drainage
- Mono-pitch (lean-to) — one sloping surface
- Gable / saddle roof — two sloping surfaces meeting at the ridge
- Hipped roof — four slopes with two short ends sloped down to the eaves
- Pyramid (tent) roof — four triangular slopes meeting at a single point
- Mansard roof — two pitches per slope, steep below and shallow above
- Cross-gable roof — two gable roofs intersecting at right angles
- Inverted (butterfly) roof — two opposing mono-pitches meeting in a valley
Selection considerations
The choice of roof shape depends on many factors:
- Local planning policy — local authorities often prescribe a roof shape appropriate to the area
- Usability of the loft — a gable or mansard roof yields more usable space than a pyramid roof
- Construction cost — a flat or gable roof is generally cheaper than a hipped or cross-gable roof
- Water drainage — the steeper the roof, the faster water is shed
- Energy performance — a south-facing pitched roof is well suited to PV panels or solar collectors
Elements of a roof shape
Every roof shape is built from a combination of:
- Roof slope or pitch surface — the sloping plane itself
- Ridge — the upper horizontal intersection of two slopes
- Hip — outward-projecting edge between two slopes (hipped roof)
- Valley — inward-running edge between two slopes (cross-gable)
- Eaves — lower edge of the slope
Application
The roof shape is chosen in the first sketch phase of a design, because it has major consequences for the façade layout, the volume and the appearance of the building.
Related terms
- Roof slope
- Gable roof
- Hipped roof
- Flat roof
- Mansard roof
- Roof pitch
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