The fabric cover on a steel framed structure is, of course, a critical component of the building. We look into some of the important factors that affect the longevity and strength of a fabric cover, and the difference between different types of fabric materials.
When buying a fabric structure, a lot of focus is put on the steel trusses e.g. the quality, engineering, installation, etc. But what about the fabric roof itself? Being a key and main component of your structure, it’s important to understand how the fabric covers are manufactured, how they are installed, and why some materials and methods are preferred over others. How is a fabric cover made?
Britespan’s Fire Retardant (FR) and Non-Fire Retardant fabric is made from high density polyethylene tapes, coated on two sides with low density polyethylene and FR additives. The coating thickness is 4 mils, with the fabric covers total thickness being 24 mils (0.610mm).
The scrim, which is the woven part of the material, is constructed of individual tapes. The unique composition of the tapes and how they are woven together give the fabric its tremendous rip, tear and puncture strength. The specialized 4 mil coatings provide a more uniform and thicker protection layer for the scrim, increasing ultraviolet protection. “The thicker coatings are more resistant to abrasion damage during both fabrication and installation of the fabric cover,” says Joy Lindsay, Fabric Coordinator at Britespan.Welded vs. stitched
“Always make sure the fabric covers being used are heat welded together at their seams and pockets as opposed to stitched,” says Joy. There are some fabric building suppliers that stitch the fabric covers at the seams and/or pockets. “By welding the fabric, we are able to create a stronger seam and pocket, as opposed to stitching, significantly reducing the risk of the seams coming apart over time due to sun exposure and deterioration of the thread and/or the needle puncture holes to the fabric and coating.”
As the tension of a fabric cover is a critical part of a building, it is especially important to ensure the fabric is heat welded and not stitched. “Under tension, heat welded fabric covers have tested seams that are as strong or stronger than the fabric. A stitched cover under tension, however, will have the fabric pulling at every stitch of the seam,” says Joy. Installation methods
The tension of a fabric cover affects the snow shedding properties and longevity of the cover, so ensuring it is installed with proper tension is important. Make sure you are working with an authorized dealer and installer who have the training and experience to install the fabric cover and the structure correctly.
Fabric covers are typically pulled mechanically by a crew using a system of ropes and pulleys (block and tackle), to ensure the covers are pulled over the building or through extrusions evenly, and do not snag or get stuck on the trusses or components
The covers may be ordered as panels and kept in place with an extrusion joint system on the truss, or as a single cover up to 144 feet of the buildings length. Many factors have a bearing on which cover style is most appropriate. Single covers are most suitable for arched buildings, and have the advantage of speed and cost. "Panel covers are most suitable for buildings over 80 feet wide or with straight roof lines, and may have advantages depending on the use and site of the building," says Joy. This is something to discuss with your Britespan authorized dealer. Polyethylene vs. Poly Vinyl Chloride
The difference between a fabric cover made from Polyethylene (PE) and Poly Vinyl Chloride (PVC) are mostly an important factor when it comes to fire reduction and environmental impact.
Should a fire ever occur in a fabric structure, a Polyethylene cover will allow the fire and flames to escape without spreading across the rest of the cover, creating a hole in the cover that can be repaired with a patch kit. PVC covers on the other hand can be highly flammable unless it has a specialized coating.
Also, a Polyethylene cover has very little environmental impact and is 100% recyclable. There are no toxic chemicals in the production of a Polyethylene cover, as opposed to a PVC cover which some studies have shown to be highly toxic and carcinogenic.Joy Lindsay is the Fabric Coordinator at Britespan Building Systems Inc.
To learn more about how Britespan can help you with your fabric building needs, visit www.britespanbuildings.com, or call us toll free at 1-800-407-5846