Staying in control with fabric cladding

by brittney_cutler | March 4, 2022 8:00 pm

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By Ben Fox and Ellie Fox

Tension fabric structures have served a key role as a cost-effective facility solution for years. In some cases, users have turned to fabric buildings when brick-and-mortar construction is not economically feasible or would take too long to complete. In other cases, fabric is more suitable to the application in the first place, because its translucency provides natural daylighting or due to the inherent corrosion-resistance of fabric cladding.

The fabric building market remained stable, but also stagnant, for a long time. Most companies in the industry were content to stay in their lane, with advancement efforts mostly focused on providing a slightly modernized version of the same basic niche product that has existed for decades.

In the last decade, technology, new materials, and improved methods have allowed fabric buildings to become a practical option for many construction projects.

These innovations have given the industry a needed push forward, but they have also created new challenges as companies work to learn new processes and properly implement them. At the end of the day, a building is only as good as the people behind it at every step of the design, manufacturing, and installation processes. While enhanced approaches to construction should theoretically expand the life cycles of buildings far beyond that of traditional fabric structures, quality control is paramount to ensure what is being promised is being delivered.

The importance of metal building software

The biggest step forward for fabric structures occurred with the incorporation of rigid-frame engineering, a hallmark of conventional architecture. Traditionally, fabric buildings relied upon hollow-tube, open-web truss frames riddled with subjective designs, leaving ample room for interpretation when evaluating their structural integrity.

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The move toward using rigid-frame I-beams and metal building software (MBS) instead of web truss instantly brought more credibility and engineering certainty to fabric buildings. Engineering professionals were now able to look at the plans for fabric structures, universally understand them, and trust the I-beam frame would stand the test of time.

The change allowed for more engineering flexibility and customization. Web truss designs were typically only available in standard, off-the-shelf size configurations, always in a basic hoop shape. Rigid-frame designs, by contrast, begin with a clean sheet and can be fully optimized from the beginning to meet the end user’s exact needs and specifications.

Using finite element analysis (FEA) software, designers can modify the structural framing of a fabric building in numerous ways like conventional brick-and-mortar buildings. Features such as lean-tos, offset peaks, and variable column heights can be incorporated. Thicker steel beams can be applied where needed to account for hanging or collateral loads at specific points on the frames, rather than over-engineering every beam. Rigid-frame buildings can also be designed much larger than web truss structures, making it possible to accommodate higher ceilings or longer clear spans.

Taking control with framing structure

It is one thing to have greater building design capabilities, but it is another for the product to be correctly fabricated as intended. In addition to offering a superior I-beam framing structure, some manufacturers have sought to enhance their quality control measures by bringing their steel beam manufacturing in-house, rather than outsourcing.

Quality control has become a challenge for the fabric structure building type because the materials and components are sometimes shipped from different suppliers directly to the jobsite. It is important to perform a quality evaluation of the materials prior to the start of construction.

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With the goal of ensuring better quality control, leading manufacturers have invested in their own on-site facilities and employ their own full-time Certified Welding Inspectors (CWI) to thoroughly inspect the varying I-beams for every project. Having inspectors on site has provided manufacturers with the flexibility to accommodate requested modifications that impact the final design required for the steel frame.

Critical corrosion prevention

Such an investment becomes even more important when one considers the common applications for fabric structures. While some markets, like event centers and sports and recreational facilities, often require the steel framing to be enclosed within the building’s fabric-cladded walls, it is commonplace in other industries for the I-beams to be left visible and exposed.

For applications such as commodity, fertilizer, or salt storage—or locations in humid, high-moisture environments, like wastewater treatment plants—corrosion concerns are a significant challenge for the steel frame.

The older style hollow-tube truss frames were notorious for hidden corrosion originating inside the tube. I-beams are made of solid steel to eliminate this, but their surfaces still must be treated to protect against corrosive elements. Hot-dip galvanizing was the go-to method for this protection for decades. In recent years, the industry has shifted toward coating I-beams with epoxy paint.

Galvanizing adds a thin layer of zinc around the steel. That layer is sacrificed over the course of several years, with corrosion gradually eating it away. In effect, galvanizing is a long-term stopgap, slowing down the corrosion process as much as it can. Epoxy paint is consistently preferred as a corrosion-fighting solution because it creates a true barrier between corrosive elements and the steel framing members, thereby providing a much higher level of protection.

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Epoxy coating is not new but is frequently considered cost-prohibitive for many fabric building customers when the only way to get it involves outsourcing. When manufacturers apply the epoxy coating in-house, the overall cost may be lower.

Equally important to a project’s ultimate longevity is the ability to control the quality of the paint job. Companies with this capability no longer must rely on a third party to do the work, but rather can bank on their professional expertise to hone in on the correct blast profiles and epoxy coating methods when preparing the I-beams for eventual shipping and installation.

Fabric self-fabrication

The story of how epoxy coating became more cost-effective is not unique in recent fabric building history. Certain polyvinyl chloride (PVC) fabric materials have followed a similar path to affordability, after previously having been reserved mostly for higher-end building projects due to higher costs.

Polyethylene (PE) fabric has traditionally been the most used material for cladding the roofs and sidewalls of tension fabric structures. Compared to the heavier yarn of PVC, standard PE material is relatively thin, with three layers comprising a fabric weave and top and bottom coatings. Its life expectancy is about 15 years.

A newer PVC on the market has seven material layers to provide increased tensile strength and longer service life. Further, as more in-house fabrication has emerged in the industry, fabric structure manufacturers can handle all the necessary panel cutting and prep of this fabric themselves, helping them to now offer PVC cladding to clients at lower prices than in the past.

Going hand in hand with lower costs is a better level of quality control. Manufacturers can cut PVC fabric panels to their specifications, rather than relying on a third party to handle the task. In-house personnel can review drawings and paperwork prior to fabrication, and in cases where they work under the same roof as the design engineers, can immediately discuss any issues without causing major project delays.

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Having their own controlled environment for fabrication is another advantage toward ensuring quality. Common procedure is for fabric to be tested at the beginning of each day, at each new roll, and during any significant temperature changes observed throughout the day. Humidity and temperature are kept as consistent as possible in the plant as fabric panels are produced, and the final fabric panels can then be examined by the original building manufacturer before shipment.

Putting it together

Much like the design and manufacturing phases, the final piece of fabric building quality control comes down to a combination of “how” and “who” questions:

How is the fabric attached to the building frame?

Who is erecting the building?

Many fabric buildings use a panel attachment system, commonly featuring 6-m (20-ft) wide fabric panels, which are connected to each frame by sliding through an aluminum keder channel.

A traditional method for attaching the extrusion channel to the frame was using self-driving screws, which were problematic for a variety of reasons, including the fact water could settle in the hole created in the aluminum around a screw, eventually causing corrosion. An even bigger flaw emerged when some buildings had to have trusses twisted out of plane to install the panels and apply horizontal tension to the fabric.

Beyond the attachment method, the actual people handling the installation—and their experience or lack thereof—can come into play. Many suppliers hire local subcontractors to have their buildings erected on-site. Some manufacturers leave it to the customer to hire their own assembly team.

Some manufacturers have in-house fabrication crews, which is an ideal method of construction for this building type. Their internal knowledge and expertise make it easier to get every detail right, helping to ensure a complete chain of quality control from start to finish.

Going beyond

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Fabric building companies that have invested in manufacturing facilities and experienced personnel have an inherent advantage in maintaining quality control. They also are more likely to communicate and interact as a cohesive team, using feedback not only to improve existing processes, but to continually innovate into new areas.

Rigid-frame fabric buildings are on the rise in new applications. PVC fabric is now a cladding option for complex structural designs that would have been difficult to conceive of just five years ago. Improvements in technology and methodology have opened more doors for tension fabric structures. The ability to handle more tasks internally—thereby elevating the quality control of every project—is making it possible to approach these new horizons successfully.

Authors

Ben Fox is the founder and president of Legacy Building Solutions. Along with two-plus decades of fabric building experience, he notably created the process for applying fabric cladding to rigid steel frames. He can be reached at bfox@legacybuildingsolutions.com.

Ellie Fox is the chief operating officer of Legacy Building Solutions. With 10 years of experience in the fabric building industry, she oversees operations throughout the company. She can be reached at efox@legacybuildingsolutions.com.

Source URL: https://www.constructionspecifier.com/staying-in-control-with-fabric-cladding/

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