Awning and canopy design basics
Fabric Architecture | Sourcebook 2002
Distinguishing between an “awning” and a “canopy” is easy—though agreeing upon the distinguishing characteristic(s) is not. There is no definitive rule. Clients, fabricators, designers and architects may see the same form but disagree on the name. One common approach defines an awning as the structure providing coverage for a window, whereas a canopy provides coverage for a door. Another approach defines awnings by their support points, all of which rely on a single building, while canopies require external support points, such as stanchions and poles.
Tensile forms and other non-traditional designs further complicate the issue, as do umbrella structures and solar shading systems. In the end, however, they all play the same functional role, even though their forms do not follow traditional classifications.
One recent successful deviation from tradition can be found acting as the entrance canopy for the German Federal Chancellery. The tensile canopy does not have any support points on the primary structure, but clearly it serves to provide elemental protection for arriving dignitaries.
Another example of an awning/canopy that makes classification problematic, yet exemplifies the functional role the structure plays, is a canopy first shown in the January/February 2002 issue of Fabric Architecture. The canopy uses one very prominant external support point, making it to many in the field not a canopy. Many fabricators who define a canopy as a structure with external support points demand at least two support points be located off the main building. Regardless of the editorial debates and changes in design approaches and material selection, establishing the basic shapes that characterize fabric awnings and canopies is enough to foster discussion between clients, designers, fabricators and architects. The familiar triangular, or traditional stationary awning, and the traditional entrance canopy govern nearly all other variations on shape: dome, elongated dome, convex, concave, quarter round/convex.
The illuminated awning, or backlit, features a lighting system behind the fabric structure. Some-times called “flexible-face signage,” it is typically used as commercial signage.
Retractable awnings resemble traditional triangular structures except that they rarely have side fabric panels. They also include a manual or electric cranking system that allows them to be folded up or retracted.
Fabric tensile structures
Fabric tensile structures can be designed to function as shade structures, “high-tech” awnings and canopies, cabanas or small tents. When attached to an existing building, fabric tensile structures often are referred to as “tensile awnings.”
Used primarily as shade and decorative devices for commercial and residential patios, new umbrella designs offer a wide variety of styles with high-tech frames and fabrics. They are still chiefly used for patios, but their aesthetic range has broadened.
Solar shading systems
Solar shading systems comprise a variety of fabric (and, in some cases, nonfabric) structures, all designed to fit on or over windows. They can be interior or exterior systems. Types include “kick-out” retractable awnings, greenhouse covers and folding shade panels. Many of these systems are computer- or sensor-controlled, automatically opening or closing in response to the sun’s brightness. In Europe, especially, these systems are often plugged into central, whole-house heating, air-conditioning and security systems.
The chief goal in frame design is to achieve the lightest structure with the greatest strength. Other considerations: corrosion resistance, weldability, shape and price.
The frame has three key parts:
- the front bar, the termination to all the bows and rafters, which carries the load;
- the return bar, which ties to the building;
- the bows and rafters, the connecting areas that determine the structure’s shape.
Although wood or plastic is used in some cases, practically all framing materials are made from either steel or aluminum.
Four types of frame material are recommended for general use:
- mild steel tubing,
- steel pipe,
- high-strength cold-formed steel tubing,
- aluminum tubing.
Frame elements are joined through welding or special connecting fittings. The overall awning design determines the size of the frame and the amount of metal used.
For example, an awning built for year-round use in a region known for snow will often need more closely placed ribs in order to support the snow load.
Most anchoring is done using tried-and-true methods. Projects having especially heavy weights and/or unusual spans typically will require an engineer’s help.
The choice of an anchoring system will depend on whether the parent structure is clad in brick, wood, concrete, steel or other material.
It is essential that the anchors be attached to a building’s structural element. The best awning anchor for just about any building is a through-bolt, which is drilled through the entire structural support surface and fastened with a nut on the back. This, however, isn’t always practicable.
Perhaps the most widely used anchorages are brackets, especially the Z bracket. For anchoring in structural brick, hard steel self-tapping anchor screws or expansion bolts are recommended.
Another option is an adhesive anchor, which uses epoxy to keep anchoring screws in place. This option, however, can make removing the awning system difficult, should a client desire remodeling in the future.
The three types of loads awnings and canopies need to withstand are wind, snow and ponding. (In certain regions, seismic loads also may deserve consideration.)
Ponding occurs when rain or melted snow collects in the fabric, causing it to sag and adding a weight load to the awning structure.
Since local codes and building officials define the loads and how they are calculated, consult the appropriate sources. (In most projects, the fabricator/installer is responsible for verifying load codes for awnings and canopies.)
When designing a fabric structure to withstand loads, consideration must be given to the surroundings. Snow loads will be lower in open areas, where snowfall can blow off the structure, while wind loads will be lower in built-up environments, where nearby buildings can provide a sheltering effect.
For canopies and non-retractable awnings, there are six chief methods of attaching fabric cover to frame: lacing, track systems, screws, staples, staple-in extrusions, and snaps or hook-and-loop fasteners.
Fabric and fabric selection
Fabric choice depends on the application: interior or exterior, illuminated (backlit) or standard commercial/residential project.
Fabrics used in illuminated awnings and canopies differ greatly in translucency and slightly in weight. Fabrics designed specifically for illuminated awnings, such as vinyl-coated and vinyl-laminated polyester, maximize light translucency.
Although traditional cotton duck, or canvas, still is used—especially when specifiers want a traditional look—synthetics now dominate the market for both residential and commercial awnings and canopies.
Synthetics have been designed to be more resistant to color-fading, mildew, flame and wicking (the fabric’s capillary-like absorption of moisture).
Perhaps the most widely used synthetic is solution-dyed acrylic because of its wide variety of vibrant colors and its canvas-like texture.
Fabrics also can be finished with a clear topcoat for added durability and cleanability. Available topcoatings include acrylic, PVF (polyvinyl fluoride, also known by its brand name, Tedlar) and PVDF (polyvinylidene fluoride).
Graphics—for awnings, canopies, banners, fabric structures
The chief methods for applying graphics to awnings and canopies include handpainting, spraypainting or air-brushing, screenprinting, heat transfer, radio-frequency (RF) sealing, cut-out lettering, ink jet processes, and eradicating.
The application of graphics has become extremely intricate in the past decade, giving architects plenty to think about when designing for retail projects, which often require building in room for flexibility, such as scrim dividers and large banners. Digital mapping is common now and grand format graphics projects are cropping up in building-length advertisements and civic displays. In many projects, more than one graphic method is used. Designing architectural spaces that allow facilities to incorporate environmental graphics for temporary changes gives a structure a longer life, whether it serves retail, institutional or commercial clients.
For added commercial effect, awnings and canopies can be backlit. Lighting is attached to the support frame, beneath the fabric cover. Because of its low expense, low temperature, and high durability, fluorescent lighting is the most widely used; however, any kind of lighting may be used for illuminated awnings. Other options: halogen or special-effects lighting.
Such applications require fabrics that are sufficiently translucent-vinyl-coated or vinyl-laminated materials. Typically, lighter-colored materials are more translucent and capable of greater brightness than darker ones.
Partial backlits are possible as well, using opaque fabric for the awning or canopy cover, and more translucent fabrics in graphics or accent areas.
The chief challenge of backlits is minimizing the shadows frames can cast on the fabric. The most common method for “hiding” frames is designing them so that the frame bows fall upon the fabric’s heat-sealed seams. The frame also must be hidden from below, so that it is not visible to those walking underneath. To hide the frame this way (as well as the lighting, wiring, etc.), use a soffit.
The most common kind of soffit is eggcrating, a plastic grid material that allows air to flow through. Other materials, such as opaque Plexiglass, also can be used.
Where necessary, install a draining system in the awning to prevent pooling atop or in back. Drains also are installed if the back of an awning meets an irregular building surface.
Drains can add weight to an illuminated awning. So can the lighting system. Lighting systems often are attached to the building wall. When they are not, the fabricator must make sure that the frame is heavy enough to support the lights.
Lighting need not be restricted to backlighting. A number of decorating methods can create subtler effects.
For instance, low-voltage linear lighting (also called tape lighting) can follow the lines of the awning, or ribs, to form more unusual patterns.
Awnings and canopies also can be accented with traditional neon or cold cathode neon tubing, the latter being more flexible and available in 50 color variations.
Other options include fiber optics and spotlights.
For more information regarding awning and canopy construction, materials, specification assistance, or to find a fabricator in your region, contact:
Professional Awning Manufacturers Association (PAMA)
1801 County Rd. B W.
Roseville, MN 55113-4061
fax +(1) 651/631-9334