Saw-tooth roof

An example of the sawtooth form is this factory built for Morris Engines Ltd., at Gosford Street, Coventry in 1923.

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.

Advantages

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 north, is designed to provide uniform, natural light over a large area, without the problems of direct sunlight and its heat. 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.^[1]

History

19th century

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...'^[2] 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.^[3]

Decline and readoption

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.^[4]

The sawtooth design, often seen on factory roofs, has won praise for its potential for renewable energy. Judges of the British Construction Industry's award recognised that the distinctive shape offers potential for solar panels to be installed.^[5]

Sawtooth roofs, in which opaque modular elements are combined with transparent surfaces, whether inclined or in various shapes, have become prevalent again. The exact dimensioning of these roofs is extremely important both in terms of energy savings, due to the reduction in electricity needed for artificial lighting, and as regards vision quality.^[6]

Examples

The Central Telephone Exchange, Melbourne provides an early example approximately 1919 of a reinforced concrete sawtooth roof.^[7]

The eponymously named Sawtooth Building is located at 930 Dwight Way, Berkeley, California, and also known as the Kawneer Manufacturing plant.^[8] Early 20th-century industrial building in Japan often feature this design.^[9] A sketch of the Saw-tooth roof form is available from the Ministry of the Environment in New Zealand.^[10]

References

Wikimedia Commons has media related to Shed roofs.