Quantities
Rectangular wall + triangular gable
- where
- net wall area (m²)
- width (m)
- eaves height (m)
- gable rise (m)
- openings (m²)
Explain this equation
This works out the net face area of a gable end: a rectangular wall up to the eaves with a straight-sided triangle on top, less any openings. Use it when ordering units for a gable wall.
b is the width of the wall, h is the height up to the eaves and r is the gable rise, measured vertically from the eaves to the apex. A_o is the total area of openings in the whole face.
The face splits into two shapes. b × h is the rectangle below the eaves. The gable is a triangle with base b and height r, and any triangle is half of the rectangle around it, hence b × r / 2.
A 6 m wide wall, 2.4 m to the eaves with a 1.5 m rise, is 14.4 + 4.5 = 18.9 m²; less 2 m² of openings leaves 16.9 m².
Watch out: r is the vertical rise, not the length of the sloping verge. Other shapes need splitting up.
Calculate a symmetrical or off-centre triangular gable above a rectangular wall.
Enter your values to see the result.
Good to know
Gable rise is measured vertically above the eaves. Only use this for straight-sided triangular gables.
Sources
- Geometry / arithmetic
Estimates are not design approval or British Standards compliance checks. Structural arch, retaining-wall, wind, foundation, lintel and masonry-capacity design are not performed. Use the project engineer’s specification.