Advantages of Tension Fabric Buildings

In the 1970s, rural North America began seeing a proliferation of sway-back barns – the old hip roof barns that had reached their 30-50-year lifespan and the trusses had given way, sagging in the middle like a saddle. In the 1990s, we saw the invasion of sagging Quonsets, with the same swayback saddle appearance, as the steel and aluminum corroded and the rivets began to pop. In the 1990s, a new design emerged to replace these antiquated utility buildings: the tension-fabric or polymer-fabric structure.

Fabric buildings offer a number of advantages over steel or wood construction, not the least of which are cost and versatility.

In Canada, weather presents a huge challenge. In summer, extreme heat and abundant sunlight curl asphalt shingles, dry and crack timber, warp steel. The metals transmit both the heat and the cold, making for significant problems in controlling internal temperature and humidity. Wood rots in high moisture environment and is often scarce in remote areas, including the north and arid areas of southwest USA. Wind wreaks havoc with the blunt-wall, solid steel or vertical wood wall and pitched-roof designs. Winter means extreme cold, and, again, steel and asphalt suffer, while concrete cracks and heaves. Poly-fabric and pvc fabric, on the other hand, withstand great extremes of temperature, moisture and other environmental conditions.

Each of the other cited materials used in construction suffer from either corrosion or deterioration in the presence of chemicals, while polymers withstand corrosive materials much better, making the building perfect for applications where salts and other harsh chemicals (including fuels) are present.

The open, curved design of many of the fabric buildings make them easier to heat, easier to insulate and less costly to light. Their design, lacking the beams and posts commonly required in large-span metal or wood buildings, is so open that equipment and storage space is maximized.

Lightweight materials allow for less costly transportation to remote sites, reducing far-north or even rural remote construction expenses. These lightweight materials also reduce need for support infrastructure, which further reduces cost.

One of the inherent advantages of a simple design is simple construction and minimal labour. Fabric buildings rise in a fraction of the time it takes to build metal or wood buildings. This further reduces construction costs.

Maintenance costs of fabric buildings fall when factoring in the need for fewer windows, less ventilation requirements, no painting, no replacement of roofing materials, less vulnerability to leaking, and lifespans that exceed wood and asphalt construction, approaches, equals and often exceeds that of even the best quality and thickest gauge of steel.

One of the occasional “knocks” against poly-fabric buildings is that they are made from petroleum products and therefore are less environmentally friendly than wood or metal. That claim is false, however. Polymers used are made from natural gas and waste gas emanating from oil wells, and use, by weight, many times less raw material than any other conventional construction form. While wood may be more “natural” (an odd claim), it deteriorates much more quickly than polymers and therefore multiplies the amount of material consumed versus fabric buildings. Almost always, wood buildings use metal or asphalt roofing. Asphalt, of course, is made directly from crude oil and is far less eco-friendly than the pvc products. Steel and aluminum, both mined metals, are far more malignant in environmental issues than pvc, and are far less eco-friendly. After factoring in the huge savings in actual materials of any sort used in poly-fabric buildings, these structures easily become the environmental choice over metal, and generally are more benign than wood buildings, per square foot.

Cost, versatility, durability and even environmental friendliness all weigh in favour of the very lightweight fabric structure, and make it the ideal choice for a multitude of commercial, industrial, agricultural and other applications.

The Basics of Tension-Fabric Buildings

Each building design and structural concept offers unique advantages and obstacles that consumers should consider prior to purchase. Poly-fabric and tension-fabric buildings are no exception. These buildings provide versatility and considerable advantages over conventional construction, yet it is important that you look at the basics of these buildings and design concepts so that you can more clearly see those advantages.

Fabric structures are as varied as wood frame or post and frame conventional buildings. Yet, tension-fabric buildings involve common “building blocks,” and the terminology used in describing these components requires clarification so that consumers may more easily decide upon their specific application preferences.

There are three primary sections to a standard fabric structure: the base or foundation, the skeleton and the coverings.  The base or foundation anchors the building to the ground and provides a solid base for the unit. The skeleton can consist of timber, steel, plastic or aluminum, or, in some instances, fiberglass or graphite (in smaller, more portable units and mobius-ball type units). The fabric may be actual fabric, mesh or films, usually with a poly, vinyl, teflon or pvc coating. The uniqueness of these structures comes primarily from the lightweight yet durable fabric, stretched and providing tension to the entire building. Wood structures, on the other hand, are compression-type construction units.

The footing need not anchor the building to the ground, some of these buildings are truly portable, consisting of a steel or aluminum platform frame on wheels, allowing them to be moved about. Commonly, the skeleton is anchored into concrete footings or pads, enabling installation of a complete flooring system. Less common is the use of pressure-treated timber foundations and even metal screw piles, particularly in soils that shift due to moisture or that are prone to frost heaving.

Today’s fabric buildings usually rely on an aluminum structure that acts like ribbing to hold the fabric tightly. In corrosive environments, the aluminum is often treated with a plastic or vinyl coating to further resist rusting and deterioration. These ribs, trusses and base plates form the skeleton of tension-fabric (also known as poly-fabric) buildings, and require rigid adherence to high engineering standards.

Often, the skin or fabric is made so that the ribs and trusses are pocketing into the design, making them stronger, longer-lived and aesthetically satisfying.

This canopy generally sees the greatest variation in quality. To be able to choose the best material for your application, it is imperative to understand the basics of the most common materials used.

Many of the pvc or polymer skins consist of a woven fabric treated with various topcoats. Canvas structures commonly are used for event venues, equipment shelters and so on. They generally can be deconstructed and reassembled more easily than the poly-fabrics, yet are waterproof and fire-retardant. PVC-laminated polyesters involve a weave of fabric coated and strengthened with vinyl films. Their strength comes from the denier, or size of filament used in the weave, as well as the number of these filaments. Much like a twisted cable versus single cable system used in suspended bridges, the weave provides strength and support for the fabric, while the layer or topcoating provides additional strength, UV protection and protection against moisture, mildew and chemicals. The quality of the poly-fabric can vary as readily as the gauge of steel or aluminum used in construction of other buildings or asphalt in roofing applications.  Nonetheless this tension-fabric design, with the proper skeleton and fabric combination, can span several hundred feet, where conventional construction would require substantially more materials and structural design.

Intuitively, fabric structures might seem more prone to destruction by storms, high wind and harsh weather than conventional buildings, but, due to their design, this is untrue. The tension imparts immense  internal strength, while the flowing design like that of an eggshell, provides consistent integrity that sheds wind, snow and rain. Consider the original tension-fabric building – the Mongolian yurt – which withstands the most violent winds of the Himalayas, because of its curved design. Most fabric structures provide that same advantage.

The three components of the tension-fabric building – foundation, skeleton and fabric – all combine to provide a uniquely cost efficient and utilitarian building, readily adaptable to a multitude of uses.