A saw-tooth roof is a

roof A roof (: roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of tempera ...

comprising a series of ridges with dual pitches either side. The steeper surfaces are glazed to admit

daylight Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation, and (often) both of these reflected by Earth and terrestrial objects, like landforms and buildings. Sunlig ...

and face away from the

equator The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...

to shield workers and machinery from direct

sunlight Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...

. This kind of roof admits natural light into a deep plan building or

factory A factory, manufacturing plant or production plant is an industrial facility, often a complex consisting of several buildings filled with machinery, where workers manufacture items or operate machines which process each item into another. Th ...

. It was therefore most commonly built during the Machine Age from the mid-nineteenth century to the mid-twentieth, when

electrification Electrification is the process of powering by electricity and, in many contexts, the introduction of such power by changing over from an earlier power source. In the context of history of technology and economic development, electrification refe ...

of factories was not yet common. Many factories of the era had little or no

electrical wiring Electrical wiring is an electrical installation of Electrical cable, cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure. Wiring is subject to safety standards for design and in ...

; their main power sources for the machinery were often

steam engine A steam engine is a heat engine that performs Work (physics), mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a Cylinder (locomotive), cyl ...

s driving line shafting, and the

lighting Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight. ...

was chiefly via daylighting through the windows. Work done at night, when necessary, was typically lit by

oil lamp An oil lamp is a lamp used to produce light continuously for a period of time using an oil-based fuel source. The use of oil lamps began thousands of years ago and continues to this day, although their use is less common in modern times. The ...

s and

candle A candle is an ignitable candle wick, wick embedded in wax, or another flammable solid substance such as tallow, that provides light, and in some cases, a Aroma compound, fragrance. A candle can also provide heat or a method of keeping time. ...

s, but many factories closed for the night. Their norm of an early working day (for example, 6 a.m. to 4 p.m.) was not merely a tradition but a functional decision based on this reliance on daylighting. The same was true of the

farmer A farmer is a person engaged in agriculture, raising living organisms for food or raw materials. The term usually applies to people who do some combination of raising field crops, orchards, vineyards, poultry, or other livestock. A farmer ...

's workday, for the same reason.

Advantages

Before electric light substituted for daylight 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. Historically they were used in industrial and manufacturing buildings as the primary light source. Some architects think that sawtooth roofs look best when grouped in rows of three or more. Sawtooth roofs allow efficient use of headroom and floor space. It is easy to install beams, columns and attractive elevations in the design of the roof. Sawtooth roofs provide for maximum headroom compared to flat roofs.

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 stated that, "Contemporaneous with the architectural improvements in mills rom 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.

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. The sawtooth design 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. 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.

Examples

The Central Telephone Exchange, Melbourne, built approximately 1919, provides an early example of a reinforced concrete sawtooth roof. The Sawtooth Building is located at 930 Dwight Way, Berkeley, California, and also known as the Kawneer Manufacturing plant. Early 20th-century industrial buildings in Japan often feature this design. A sketch of the saw-tooth roof form is available from the Ministry of the Environment in New Zealand.

References