What is a sawtooth roof?
A sawtooth roof (also called a north light roof; in Dutch sheddak) is a roof made up of a series of parallel mono-pitch roofs, each with a steep glazed face and a shallower solid face. In section it looks like the teeth of a saw. In the northern hemisphere the glazing faces north, letting in plenty of even, diffuse daylight without direct sun.
Why a sawtooth roof
In the 19th and early 20th centuries daylight was the main source of light on the factory floor, so weaving sheds, spinning mills and engineering works were given sawtooth roofs. North light gives:
- even light across the whole floor, even in the middle of a deep hall
- no glare or harsh shadows from direct sun
- less overheating than a flat roof with south-facing rooflights
Sawtooth roofs are still used today for studios, schools, museums and industrial units, precisely for that quality of light.
Weak points to watch
If you buy or renovate a building with a sawtooth roof, check these points first:
- Valley gutters. There is a gutter between every pair of ridges, so a large roof has many, often with long drainage runs. Leaves and debris cause blockages, and an overflowing valley gutter leaks straight inside. Inspect them at least once a year and provide emergency overflows
- Rainwater drainage. Downpipes often run through columns or inside the building. Have their capacity reassessed during renovation
- Snow. Snow slides and drifts into the valleys and stays there, adding load and causing leaks as it thaws
- Condensation. Single glazing and uninsulated steel sections are cold. Once the building is heated (homes, offices), condensation forms on the glass and in the gutters
- Heat loss. Large glazed areas plus an uninsulated solid face make an old sawtooth roof very inefficient. Conversion usually calls for insulating the solid face and replacing the glass with double or triple glazing; for listed buildings, agree this with the conservation authority
- Structure. Before adding weight (insulation, solar panels, a green roof), always have the load-bearing capacity checked
Modern application
The shallow solid face points south, which makes it ideal for solar panels. The sawtooth roof thus combines diffuse daylight through the glass with power generation on the solid side.
Related terms
- Mono-pitch roof
- Continuous rooflight
- Valley gutter
- Box gutter
- Daylight factor
- Condensation
- Roof pitch
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