Saw-tooth roof

A saw-tooth roof is a roof comprising a series of ridges with dual pitches either side. The steeper surfaces are glazed and face away from the equator to shield workers and machinery from direct sunlight. This sort of roof admits natural light into a deep plan building or factory.

Before daylight was supplemented or replaced with electric light in the late 19th century, consideration of good daylight strategies was essential. The sawtooth roof, with its glass panels facing away from the equator, blocks the light and heat of direct sun exposure and provides uniform, natural light over a large area. It was particularly useful in design factories and manufacturing buildings.

Sawtooth structures show apertures with vertical or angled glazing installed in a sloped roof plane. Sawtooths are most effective when used in series of three, and were historically used in industrial and manufacturing buildings as the primary light source.

British engineer and architect William Fairbairn is sometimes credited with the first designs for what he termed the shed principle possibly as early as 1827. In his, "Treatise on Mills and Millwork", of 1863, Fairbairn states that, 'Contemporaneous with the architectural improvements in mills [from 1827], the shed principle lighted from the roof, or the "saw-tooth" system, came into operation. It was chiefly adapted for power-weaving...' It was rapidly adopted during the industrial revolution for the many new daylight factories where good natural lighting was essential in the manufacturing process and large areas of enclosed space were required to house the machinery. The first documented example can be found on the Weaving Shed (and perhaps also the Combing Shed) of Titus Salt's Saltaire Mills near Bradford, which were founded in 1851.

There was a decline in its use when artificial lighting became prevalent, but the design re-emerged in the last quarter of the 20th century and early 21st century, as architects and designers placed greater importance and value in introducing natural light into buildings for environmental efficiency.

Reasons for the renewed interest in daylighting include the high cost of fossil fuels and the realization that sources of electricity have a finite life. Less tangible aspects of daylighting relate more to the human spirit and quality of life.

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