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Sidewalk Light Construction Increases Floor Space
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Builder 1921
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The high cost of land in business districts puts an extra premium on space. Consequently, when the builder draws up his plans for a structure he must give this factor careful attention. Another feature, just as important, is lighting facilities. While artificial light will serve, effort is made to provide as much natural light as possible. Builders have been able to accomplish satisfactory results in both these cases with the aid of special sidewalk, vault, and roof lights.
    Briefly, this material consists of heavy pieces of transparent glass set into steel forms and imbedded firmly in concrete. Sections can be used in sidewalks, roofs or over vaults. Because of its strong construction this material will carry a heavy load without breaking, and at the same time admit light thru the small glass lenses. Placed in sidewalks, it opens up the space underneath for use as extra sales rooms, etc. Thousands of square feet of floor space have been added to stores and other buildings by this construction.
    In a similar way the lights are used in factory, store and vault roofs.
    In laying sidewalk lights, the steel forms are laid across the girders which extend from the building out to the curbing as shown on the detail sheet on page 109. The longer the span, the more light is admitted to the space below.
This arrangement is waterproof and provides a maximum amount of glass area. The glass lenses are made of heavy glass and can be replaced very easily. They are designed differently for various uses. The galvanized forms are laid directly on the bearings and the glass then inserted into spaces provided in the steel forms. Reinforcing rods are then laid and the concrete poured into place. The forms, reinforcing rods and glass are thereby permanently joined together.
    Ample provision for expansion and contraction should be made. This is done by allowing not more than 30 square feet in one panel. Less area is even more desirable. Regardless of bearings if the edges of the slab are not clear or come in contact with some other construction, a joint of not more than ½ inch or less than ¼ inch should be provided and filled with expansion compound. These joints provide opportunity for action of the construction caused by contraction and expansion and are necessary to prevent cracking of the glass.
    Tables of safe loads for this construction and other specifications are furnished by the various manufacturers.
    Many accessories are fitted with this glass to provide light; for instance, sidewalk doors, coal-hole tops, etc. The glass lenses are made in many shapes, the most popular being the square and round shapes.
American Builder, January, 1921, pages 107-109