The F word in Fabric Structures

When it comes to the letter “F”,  Besides Fun, the FabricArchitect can think of a couple or more things:

  • Failure
  • Fabric
  • Frei Otto

Failure:

No one likes talking about structural failures but when a couple of fabric structures collapse due to unprecedented snow and ice storms, some things should be discussed. I recently read an article in the New York Times regarding ice falling from skyscrapers in New York. The temptation is to fault the designer, architect or engineer.

While fabric roofs have collapsed, traditional roofs are also collapsing too. The damage has been less below a fabric structures and they are much easier to repair and replace.

Fabric Structures are designed to the latest codes and these are 100 year storms we are experiencing. However, as one Architect friend put it, “Is there something in the design and engineering of these structures or is it just an Act of God or maybe the fact codes need to be changed to adjust to global warming snow levels?

The most important concern resulting from building failure is life safety . I believe that a fabric structure provides a great cost effective solution for shade and shelter and since it relies on few structural members its record for structural damage and loss of life is very low.

Frei Otto

I couldn’t wait until we reach “O” to discuss Frei Otto! He is the forefather, founder and pioneer of Tension Fabric Structures. His work is the reason I got into this business. From the German Pavilion at Expo 67 to the 1972 Olympic Stadium in Munich, he is most likely responsible for the hundreds (maybe thousands) of designers and engineers that have carried the torch of lightweight structures around the world. I have always wondered how many people were truly influenced by Lightweight Structure advocates like Frei Otto and Buckminster Fuller (another F). Architect Phillip Johnson once said “in Architecture, You cannot not know history”. In Fabric Structures, you cannot not know Frei Otto.

Fabric

This is such a huge topic. Architectural fabrics in common use today include:

  • PTFE
  • Silicone-coated fiberglass
  • Woven PTFE
  • PVC-coated polyester
  • PVC-laminated polyester
  • Theatrical draperies
  • Stretch fabrics (spandex)
  • High-density polyethylene (HDPE)
  • ETFE

Without trying to reinvent the wheel, the best way to determine which material to use is to see what has already been used for the building type you are considering.

If you are interested in structures such as tents or umbrellas where the main objective is to provide temporary, nomadic shelter, you are probably looking at vinyl laminated or coated polyester.

If you are researching awnings and canopies, the options are endless. You are most likely to hear words like acrylic canvas and backlit fabrics and materials which you can apply graphics to.

If shade is your primary concern, the buzz word is structural mesh, high density polyethylene (HDPE), perforations and % of light transmission.

For warehousing, industrial applications and temporary buildings, a common term may be clear spans or pre-engineered fabric buildings with materials that are mold and mildew resistant.

The interior and lighting industry have their own variety of fabrics where flame resistance, UL ratings and % of reflectance are the most important issues.

Air and Tension Fabric Structures rely heavily on its fabric’s structural characteristics and tensile strength, sound absorption and solar transmission play a major role in their selection.

Material Choices

OK, so now you’ve seen what’s out there already, but you want to make a statement, solve your clients needs and have unlimited funds.

Yeah, right!

What material do you use?

Is your project near the water?

Is it meant to last 5, 10, 20, 30 years?

Do you want to see it from afar or do you want it to be dark inside at noon?

These are all important questions one should answer before you even start.

Make Mine Non Combustible

In most States, permanent, totally enclosed structures require a “non combustible” or Class A/B rating according to Building Codes. The most recognized and accepted material used for Architectural Applications is Teflon Coated Fiberglass or PTFE.

Recognized manufacturers include Saint Gobain, Verseidag, FiberTech, Chuko and Taconic. Teflon comes to the site brown like a pair of khakis but bleaches to a milky white over time (usually 4-8 weeks). The biggest problem with Teflon is that it is stiff and brittle and must be handled very carefully to avoid breaking the fibers. The best part is its life span (30 years) and “self cleaning” attributes.

Other “non combustible” materials include Silicon Coated Fiberglass, Sefar’s Tenara and  ETFE.

Make Mine PVC or PVDF

The majority of fabric structures being considered today are for uses which do not require complete enclosure. That means, they are most likely “open air” or do not require a Class A rating. Class C is the most common rating and NFPA 701 is the most accepted certificate for most Fire Marshals. Vinyl coated polyester (PVC) is the most common material used on the market today.

What’s not to like?

The material comes in a variety of colors, strengths, weights, thickness, perforations, translucency and textures. The material is pliable and stretches quite nicely. You can find material with 10, 12 and even 15 year warranties. You can find material that is 50 to 100” wide so you can have few, fewer or the fewest amounts of seams.

Manufacturers include Ferrari, Mehler, Naizil, Seaman and Verseidag, to name a few. These are the names most seen on Specifications, which means that these companies are directly marketing and assisting the Architect in the early stages of the design.

PVC comes in a variety of top finishes: acrylic, PVDF and PVF film. There is much debate about top finishes but all manufacturers agree that they are needed to protect the base fabric from UV degradation, water and wind.

Frankly, it’s all about the coatings.

PVF is a film applied to the main fabric while acrylic and PVDF are coatings. Both PVF and PVDF claim to be “self cleaning” or provide the base material with a much cleaner and maintenance free surface but both require additional work in the shop which may be unknown to the Architect.

Both top of the line PVF and PVDF require that the top coat or film where two panels are to meet be grinded off in order for them to be RF welded. This is time consuming and requires great care in order to keep the seams clear of dirt, model and mildew. There are “weldable” PVDF but their warranties are not as long as the high tech top coats.

PVC Structures love graphics and provide a great backdrop for projected images.

Made in the Shade

Today, more and more fabric structures are being designed for shade only. Structural mesh and perforated fabrics are being specified because of the need for shade, the need to allow the elements to go thru the material and the need for a space to “see thru and be seen”. The material most often used is high density polyethylene (HDPE). Manufacturers include Multiknit, Coolaroo and Shadesure. This material is a higher grade mesh than what one would see at a home improvement warehouse or at an outdoor furniture store.

HDPE is used for playgrounds, areas requiring hail protection, schools, day care centers as well as theme parks and spaces of public assembly. Mesh is hot so you can stay cool. Mesh comes in colors, fire rated and with different perforations. It has a life span of 8-10 years and in most cases lowers the size and loads on the structural system and foundations because it takes less wind.

Keep it simple

If you want to keep it simple, then work with materials which do not rely on their structural characteristics for its stability. These materials are usually clad on a frame. The materials are usually vinyl laminated polyester, acrylic coated canvas, and materials with a light topcoat. Sunbrella and Weblon are common brands. The material has less technical information available for applying them to fully engineered lightweight structures but when used as a cladding on a frame, they offer many opportunities to the Architect. One can apply graphics to the material, bring texture to the surface or make something truly unique.

Keep it inside

If you want to look at materials for interior application, look no further than the industrial fabric industry and Theatrical Drapery. There are lightweight PTFE materials used for ceilings in dome stadiums, PVC fabrics are used for interior tensioned fabric sculptures while theatrical drapery materials from companies like Rosebrand and Dazian are used for a softer look. Spandex/Lycra is another common material used for transforming temporary and permanent spaces but require the material be fire treated prior to fabrication.

The Future of Fabric?

Lastly, it doesn’t hurt for the Fabric Architect to dream about the future of architectural fabrics. My wish list would include “Smart” fabrics, fabrics that change color according to weather, light or mood. Fabrics made with optic and photovoltaic fibers. Materials with longer life spans, higher tensile strength, improved self cleaning, higher translucency and more environmentally friendly.

The future of Architectural Fabric Structures depends on the continuing effort of manufacturers to improve its existing products and introduce new materials.

Less is more, lightweight is more. Fabric is even better.

We go to “G” next.

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2 responses to “The F word in Fabric Structures

  1. every passing day i found your blog more interesting and cannot wait till we reach “Z”….thanks

  2. Pingback: Canvas buildings | CftcStx

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