A roof slope (also called a roof pitch surface or roof plane) is a single continuous inclined surface of a pitched roof, bounded by ridges, hips, valleys, eaves and/or gable verges. A roof may consist of one or more roof slopes, depending on the chosen roof shape.
Number and position of roof slopes per roof shape
The number of roof slopes is directly related to the chosen roof form:
- Mono-pitch (lean-to) — one roof slope
- Gable / saddle roof — two roof slopes (front and back)
- Hipped roof — four roof slopes (two long and two shorter triangular ones)
- Pyramid roof — four triangular slopes meeting at a single point
- Mansard roof — four roof slopes with two different pitches per side
- Cross-gable roof — multiple slopes through linked roof forms
Elements bounding a roof slope
- Ridge — the horizontal top edge where two slopes meet
- Hip — the outward-projecting edge between two slopes, e.g. on a hipped roof
- Valley — the inward-running edge between two slopes (on a cross-gable roof)
- Eaves — the lower edge of the slope where the gutter or overhang begins
- Verge — the side edge along a gable wall
Build-up of a roof slope
A roof slope consists, from inside to outside, of:
- Trusses or purlins carrying the rafters
- Roof sheathing or vapour-permeable membrane
- Counter battens and tile battens
- Roof covering — tiles, slates, thatch, zinc or bitumen
Application
The shape and pitch of a roof slope influence the building’s appearance, water drainage and thermal performance, and the usable floor area in the loft. Insulation values (U-value) and roof covering quantities are calculated per slope.
Related terms
- Ridge
- Hip
- Valley
- Eaves
- Roof pitch
- Roof shape
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