An awning or overhang is a secondary covering attached to the exterior wall of a building, typically for shade (shadow). It is typically composed of canvas woven of acrylic, cotton or polyester yarn, or vinyl laminated to polyester fabric that is stretched tightly over a light structure of aluminium, iron or steel, possibly wood or transparent material (used to cover solar thermal panels in the summer, but that must allow as much light as possible in the winter). The configuration of this structure is something of a truss, space frame or planar frame. Awnings are also often constructed of aluminium understructure with aluminium sheeting. These aluminium awnings are often used when a fabric awning is not a practical application where snow load as well as wind loads may be a factor.
History
Ancient world Awnings (or marquees) were first used by the ancient Egyptian and Syrian civilizations. They are described as "woven mats" that shaded market stalls and homes. A Roman poet Lucretius, in 50 BC, said in his poem De rerum natura "Linen-awning, stretched, over mighty theatres, gives forth at times, a cracking roar, when much 'tis beaten about, betwixt the poles and cross-beams". Among the most significant awnings in the ancient world was the velarium, the massive complex of retractable shade structures that could be deployed above the seating areas of the Roman Colosseum. Made of linen shadecloths, timber framing, iron sockets and rope, the system could effectively shade about one-third of the arena and seating; another third could be shaded by the high surrounding walls, providing a majority of seats some shade on a blinding afternoon. It is believed that sailors, with their background in sailmaking and rigging were employed to build, maintain and operate the velarium.
Early 19th century
Awnings became common during the first half of the 19th century. At that time they consisted of timber or cast iron posts set along the sidewalk edge and linked by a front cross bar. To lend support to larger installations, angled rafters linked the front cross bar to the building facade. The upper end of the canvas was connected to the facade with nails, with grommets and hooks, or by lacing the canvas to a head rod bolted to the facade. The other (projecting) end of the canvas was draped over or laced to a front bar with the edge often hanging down to form a valance. On ornate examples, metal posts were adorned with filigree and the tops decorated with spear ends, balls or other embellishments. On overcast days or when rain did not threaten, the covering was often rolled up against the building facade; during the winter months proper maintenance called for the removal and storage of awnings. Photographs from the mid-19th century often show the bare framework, suggesting that the covering was extended only when necessary. Canvas duck was the predominant awning fabric, a strong, closely woven cotton cloth used for centuries to make tents and sails. Awnings became a common feature in the years after the American Civil War. Iron plumbing pipe, which was quickly adapted for awning frames, became widely available and affordable as a result of mid-century industrialization. It was a natural material for awning frames, easily bent and threaded together to make a range of different shapes and sizes. At the same time the advent of the steamship forced canvas mills and sail makers to search for new markets. An awning industry developed offering an array of frame and fabric options adaptable to both storefronts and windows.
Late 19th century
In the second half of the 19th century, manufactured operable awnings grew in popularity. Previously, most awnings had fixed frames—the primary way to retract the covering was to roll it up the rafters by hand. Operable systems for both storefront and window awnings had extension arms that were hinged where they joined the facade. The arms were lowered to project the awning or raised to retract the awning using simple rope and pulley arrangements. Because the canvas remained attached to the framework, retractable awnings allowed a more flexible approach to shading (shopkeepers and owners could incrementally adjust the amount of awning coverage depending upon the weather conditions). When the sun came out from behind clouds, the awning could be deployed with ease. In case of sudden storms, owners could quickly retract the awning against the building wall where it was protected from wind gusts. Despite their advantages, early operable awnings had drawbacks; when retracted, their cloth coverings often bunched up against the building facade. This left part of the fabric exposed to inclement weather, and deterioration was often accelerated by moisture pooling in the folds of fabric. If poorly designed or badly placed, the retracted fabric could obscure part of the window or door opening, and even if out of the way an imperfectly folded awning presented an unkempt appearance. Modern materials and designs have eliminated all of these issues.
Types
Actuation
Today's awnings come in two basic types: manually operated models, and motorized models (operated by electric motor). Each offers its own advantages. Benefits include low-cost affordability, easy adaptability to almost any deck or patio, and support arms that can be angled back against the house or set vertically on the deck or patio floor. These arms provide extra support and stability which some owners prefer in windy areas, and increase the awning's versatility by making the attachment of certain accessories available. Motorized awnings have no vertical supports. Instead, they have retracting lateral arms, creating an unobstructed shaded area. These awnings are operated by an electric motor, generally hidden inside the roller bar of the awning. The arms open and close the awning at the touch of a wireless remote control or a wall-mounted switch. Modern awnings may be constructed with covers of various types of fabrics, aluminium, corrugated fibreglass, corrugated polycarbonate or other materials. High winds can cause damage to an extended awning, and newer designs incorporate a wind sensor for automatic retraction in certain conditions.
Wind tolerance and construction
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