By Ben Fox
Two or three decades ago, it would have been rare to see a fabric-covered building anywhere, much less as an important protective structure for salt and sand storage or other facility needs for snow and ice management. But as the tension fabric industry has grown during the last 15 years, more and more entities are seeing the advantages of fabric structures — such as their non-corrosive properties and ability to allow natural light to permeate the building.
Whether utilized for material storage, equipment maintenance or some other application, fabric buildings have become a dependable and cost-effective option when a structure is needed. Additionally, the quality of these buildings has come a long way in a relatively short time. Many new trends have worked their way into the design of tension fabric structures, whether they are gradual improvements to industry staples or dramatic new strides in engineering.
Going Rigid, Getting Flexible
By far the biggest recent change with fabric buildings is the rigid frame engineering concept that Legacy introduced to the market almost two years ago. This new design trend utilizes structural steel I-beams in place of the hollow-tube, open web-truss framing that has traditionally been used for tension fabric buildings.
Why the change? Simply put, the I-beam design is almost universally accepted within the engineering community, whereas opinions on the quality of web truss design tend to be subjective. Certainly the industry couldn’t have come as far as it has without the web truss being a serviceable option as the industry standard for so long, but the fact remains that there is usually very little consensus about what constitutes a well built or poorly built web truss building.
The more durable web truss buildings on the market typically feature thicker cords and webs, but the additional steel involved usually makes them more expensive than a similar building with a rigid frame. Cost aside, the rigid frame technique effectively eliminates any questions about the structural integrity of the building. And, for good measure, the I-beam buildings have a more conventional look and feel.
Another key advantage with a structural steel design is having the flexibility to customize buildings beyond the confines of standard sizes that are generally the norm with web truss. Custom sizes are possible with web truss designs also, but almost always at a much higher price tag and with longer delivery times. The process of rigid frame engineering allows buyers to specify the exact width, length and height they require — without having to pay a premium and without waiting any longer for delivery. Offset peaks, multi-level legs and many other unique features are possible as well.
Landscape and winter maintenance contractors know that maximizing space is a critical issue. I-beam design brings another engineering advantage in the form of straight sidewalls. Where the traditional web truss building shape is an arch that leads to some unusable space along the sidewalls, a rigid frame provides straight sidewalls, clear spans and tall overhead clearances that allow every square foot to be used. The straight sidewalls also make it easy to implement side doors of any shape and size.
Rigid-frame buildings can also more easily accommodate other equipment and additional loads on the structure itself. Items like overhead cranes, conveyors and fire suppression systems can be hung on the frame. Commodity pressures can also be incorporated into the sidewalls. In a nutshell, the overall strength of a structural steel building makes a lot of things possible that couldn’t be done in the past.
A clear benefit of all fabric salt storage buildings, in comparison to metal structures, is the non-corrosive nature of the fabric itself. However, with the hollow-tube web truss, unseen corrosion can actually originate inside a tube and do its damage from the inside out. Because they are solid, structural steel beams don’t face the same vulnerability. Meanwhile, multiple coating options are available to protect the beams, including hot dip galvanizing, grey oxide primer and powder coat paint.
Putting it on
All photos provided by Legacy Building SolutionsGoing hand in hand with the I-beam design trend is the actual tensioning and application of fabric to a structure. Being able to apply fabric in straight lines on a rigid frame simplifies the process and prevents the type of chafing wear and tear that can occur when fabric is stretched over the curves of a web truss frame.
Often when fabric is stretched around a curve, the scrim is distorted and pulled at an angle that causes the fabric’s coating to crack and eventually fail prematurely. In general, fabric should be fine if it’s applied at the proper tension; but even with experienced professionals handling the installation, fabric roofs are more likely to succeed in the long run with a simple, straight-line application. That being said, one critical detail with almost all fabric structures is to ensure that proper vertical and horizontal tension is applied during the installation of fabric panels.
Another factor is the size of the fabric being applied. For example, if a 200-foot-long building’s roof is made up of only a few large pieces of fabric, it’s going to be difficult to secure it at the proper tension. Consequently there’s a very good chance the roof will begin to move around once in use. By contrast, if manageable 20-foot panels are utilized, everyone involved can have greater confidence that they will be correctly placed and secured.
The method of installation is important as well. Having nails or screws penetrating the roof is to be avoided, as this can potentially create locations for rust to start and holes that can later become leaks. A better method is to support the panels with a track that keeps the fabric out of contact with the steel frame.
Architectural fabrics also continue to advance in quality. For many years, polyvinyl chloride (PVC) coated fabric was the primary cladding choice for tension fabric buildings. But it was when polyethylene (PE) fabrics were introduced into the marketplace about 15 years that the frame-supported fabric structure industry began to blossom. With a life expectancy of about ten years and a lower cost, PE fabrics fostered expansion into bulk storage and other building applications.
During the last five years PE fabrics have greatly improved in quality. For properly installed fabric, it’s usually sunlight and pollution that are responsible for material breakdown. By introducing thicker coatings and better UV inhibitors, PE fabrics are now expected to last as long as 20 years.
As fabric structure manufacturers have gained more confidence in the expected longevity of PE fabric cladding, there’s more flexibility in making recommendations to customers trying to choose the best option between PVC and PE fabrics. With a life expectancy of 20 to 30 years, PVC coated fabrics remain the preferred option for high end building applications.
Fabric roofs have many benefits. Inherently reflective, white roofs can reflect 80 percent or more of the sun’s rays and emit at least 70 percent of the solar radiation that the building absorbs. Translucent fabric roofs can offer translucency as high as 12 percent, effectively eliminating the need for artificial lighting during daytime hours and making them an energy efficient solution.
Up and running
Generally speaking, just about everything with a fabric building is simpler than it would be with a comparable metal building. Initial delivery times after an order is placed are shorter, and an experienced crew can install a fabric building in about one-third the time it takes to erect a metal structure.
Even when designed to be permanent, fabric structures are still inherently portable. So for contractors who may need to relocate a building after a certain period of use, fabric buildings are much more easily moved than metal buildings.
From design flexibility to cost effectiveness, there are plenty of reasons why winter maintenance contractors gravitate toward tension fabric buildings. Even better, the recent and rapid evolution of fabric structure engineering practically ensures that building users can reap all the desired benefits they expect, while knowing they’re also getting a great value.
Ben Fox is president of Legacy Building Solutions (www.legacybuildingsolutions.com).