Fabric structures are constructed from engineered fibers that provide aesthetic, free-form building designs. They are custom-designed to meet structural and weather requirements. The selection of materials, design, engineering, fabrication, and installation all work together to ensure a sound structure. Common fabric materials include polyesters, vinyl-coated polyester, fiberglass, PTFE-coated fiberglass, woven PTFE, and ETFE foil. Properties of these materials like strength, weather-resistance, temperature tolerance, and recyclability determine their suitability for different applications.

2.  FABRIC STRUCTURES ARE FORMS OF CONSTRUCTED FIBERS
THAT PROVIDE END USERS A VARIETY OF AESTHETIC FREE-
FORM BUILDING DESIGNS. CUSTOM-MADE FABRIC STRUCTURES
ARE ENGINEERED AND FABRICATED TO MEET WORLDWIDE
STRUCTURAL, FLAME RETARDANT, WEATHER-RESISTANT, AND
NATURAL FORCE REQUIREMENTS. FABRIC STRUCTURES ARE
CONSIDERED A SUB-CATEGORY OF TENSILE STRUCTURE.
 A FABRIC STRUCTURE’S MATERIAL SELECTION, PROPER DESIGN,
ENGINEERING, FABRICATION AND INSTALLATION ALL WORK
TOGETHER TO ENSURE A SOUND STRUCTURE. THE MATERIAL’S
ROLE IN THE STRUCTURE’S PERFORMANCE MAKES THE
SELECTION PROCESS ESPECIALLY IMPORTANT. THIS IS
PARTICULARLY TRUE WITH TENSILE AND AIR-SUPPORTED
STRUCTURES BECAUSE THEIR MEMBRANES, AS WELL AS THEIR
FRAMES, CARRY THE LOADS.

3. Common Shapes and Forms:
• Mast Supported
• Point Supported
• Arch Supported
• Frame Supported
• Simple Saddle

4.  Mast-supported
systems
Tent-like
structures in form
One or several
peaks supported by
central poles and
perimeter cables
Typically use
compression ring or
“bale” ring

5.  Point-supported
Clear span avoids a center mast
Often hypar shaped (two high, two low connection
points)
Utilizes an exterior frame or series of peripheral masts

6.  Arch-supported
Introducing a curved compression member
Cross arches often used

7.  Frame supported
Space frame
Fabric attached to a structural frame
Structural components carry forces
Fabric is purely used as a cladding

8.  Simple
Saddle/Hypar
Double curvature
Two (2) high points,
Two (2) Low points
“Saddle” shape
Horizontal or Vertical
Minimal surfaces

9.  Polyesters
 Vinyl-coated polyester
 Vinyl-laminated polyesters
 Fiberglass
 PTFE-coated fiberglass
 Woven PTFE
 ETFE foil

10.  Polyesters
 Polyester is the most frequently used base material because of its
strength, durability, cost and stretch. Polyesters laminated or
coated with PVC films generally are the least expensive for
longer-term fabrications.
 Laminates usually consist of vinyl films over woven or knitted
polyester meshes (called scrims or substrates). Coated fabrics
typically use a high-count, high-tensile base fabric coated with a
bondable substance for extra strength. One fabric manufacturing
method places polyester fabric under tension before and during
the coating processes. The result is that yarns in both directions
of the weave have identical characteristics, giving the fabric
increased dimensional stability.
 Lighter fabrics (200 to 270g/m2) commonly are used as acoustic
and insulated liners suspended beneath a structure’s envelope.
For long-term exterior use, heavier materials are needed: 20- to
26-oz. (680 – 880gm) fabrics with top coatings of polyvinyl
fluoride (PVF, of which Tedlar is an example) or poly vinylidene
fluoride (PVDF, of which Vidar, Fluorex and Kynar are examples).
These top coatings provide a protective finish to withstand
environmental degradation.

11.  Vinyl-coated polyester is the most common fabric for producing flexible structures, such
as custom-designed awnings, canopies, walkways, tent halls, smaller air-supported
structures and light member-framed structures.
 Vinyl-coated polyester is composed of a polyester scrim, a bonding or adhesive agent, and
exterior PVC coatings. The polyester scrim supports the coating (applied initially in liquid
form) and provides the tensile strength, elongation, tear strength and dimensional stability
of the finished fabric. The scrim is made of high-tenacity, continuous-filament yarns,
which have high dimensional stability, and can be bent thousands of times without losing
any tensile properties. The base fabric’s tensile strength is determined by the size (denier)
and strength (tenacity) of the yarns and the number of yarns per linear inch or meter. The
bigger the yarn and the more yarns per inch, the greater the finished product’s tensile
strength.
 For architectural applications, base fabrics typically weigh between 2.5 and 10 oz/yd2,
with a tensile strength between 300 (2.662 N/5cm) and 650 lbs/in (5.60 N/5cm), although
fabrics intended only for tent use may have lower measurements.
 The adhesive agent provides a chemical bond between the polyester fibers and the
exterior coatings and prevents wicking of moisture into the fibers. Wicking is the capillary
like action of fiber to absorb water, which could result in freeze-thaw damage.
 The PVC coating liquid (vinyl Organisol or Plastisol) contains chemicals to achieve desired
properties regarding color, water resistance, mildew resistance and flame retardancy. The
fabrics also can be made with high levels of light transmission or complete opaqueness.
After the coating is applied to the scrim, the fabric goes through a heating chamber to dry
the liquid coating.

12.  Vinyl-laminated polyesters are used for awnings, tents and
low-tension frame structures. Technically, a laminated fabric
consists of a reinforcing polyester scrim that is calendared
between two layers of unsupported PVC film. In general use,
it refers to two or more layers of fabric or film joined by
heat, pressure and an adhesive to form a single ply.
 With an open-weave or mesh polyester scrim, the exterior
vinyl films bond to themselves through the openings in the
fabric. Heavier base fabrics, though, are too tightly
constructed to permit this lamination process, so an
adhesive must bond the exterior films to the base fabric.
 A good chemical bond is important to prevent delamination
and is critical in developing the proper seam strengths. The
adhesive enables the seam, created by welding vinyl-coated
fabric to another piece of the same material, to meet a
structure’s shear forces and load requirements at all
temperatures. By preventing wicking of moisture into the
scrim’s fibers, the adhesive prevents fungal growth or
freezing that can affect the exterior coating’s adhesion to
the scrim. In response to EPA regulations, the adhesives are
water-based.
 Using an open-weave scrim such as mesh might make these
fabrics more economical, depending on the number and type
of features required in the vinyl. What weight is necessary to
withstand abrasion and wear? Is flame resistance needed? Is
a particular color required? What width? Virtually any color,
plus UV resistance, abrasion resistance, and colorfastness
can be formulated into the vinyl, but the more of these
features incorporated, the higher the cost.

13.  ANOTHER WIDELY USED BASE MATERIAL IS WOVEN FIBERGLASS
COATED WITH PTFE (ALSO KNOWN AS TEFLON) OR SILICONE. THE
GLASS FIBERS ARE DRAWN INTO CONTINUOUS FILAMENTS,
WHICH ARE BUNDLED INTO YARNS. THE YARNS ARE WOVEN TO
FORM A SUBSTRATE.
 THE FIBERGLASS HAS A HIGH ULTIMATE TENSILE STRENGTH,
BEHAVES ELASTICALLY AND DOES NOT UNDERGO SIGNIFICANT
STRESS RELAXATION OR CREEP.
 THE PTFE COATING IS CHEMICALLY INERT, WITHSTANDS
TEMPERATURES FROM MINUS 100F TO 450F (MINUS 73C TO
232C), IS IMMUNE TO UV RADIATION AND CAN BE CLEANED
WITH WATER.
 PTFE-COATED FIBERGLASS IS AVAILABLE WITH AS MUCH AS 25%
TRANSLUCENCY, PROVIDING DIFFUSED INTERIOR LIGHT. ITS
ABILITY TO PROVIDE NATURAL DAYTIME LIGHTING AND ITS
HIGHLY REFLECTIVE SURFACE FOR EFFICIENT NIGHTTIME
INTERIOR LIGHTING CAN REDUCE ENERGY CONSUMPTION.

14.  For these and other reasons, fiberglass-based fabrics have
been the material of choice for stadium domes (both air-
and cable-supported) and many other permanent
structures, particularly in the United States. Another reason
some industry experts cite for this is a perception among
code officials that its high melting temperature and lack of
creep, or long-term elongation, make it superior to
polyester. Other industry insiders note that polyester, like
fiberglass, melts rather than burns at high temperatures,
and that properly constructed, polyester structures may be
equally durable.
 Because of the differences in how polyester and fiberglass
perform in fire-resistance tests, PTFE-coated fiberglass is
the only membrane material that currently meets the U. S.
model building codes definitions of a noncombustible
material. (The three U.S. model codes are currently being
reviewed and soon will be consolidated into one code.) This
is a more accurate reason for the PTFE-coated fiberglass
preference, but it raises questions about whether standards
applied to other building materials should be applied to
membranes.

15.  Woven PTFE
 This material is constructed of PTFE fibers woven into a
fabric. As of now, only one such material is available.
Woven PTFE combines the environmentally-resistant
advantages of the material with its ability to withstand
repeated flexing and folding, an advantage it has over
coated-fiberglass fabrics. Such flexibility makes it an
especially good option for convertible structures;
however, it is a rather expensive material and is not as
strong as either polyester or glass.
 ETFE foil
 Perhaps the newest development in the fabric structures
arena is the introduction of ETFE (ethylene
tetrafluoroethethylene), a transparent membrane with
fabric like qualities and the advantages of PTFE, such as a
self-cleaning capability. Resistant to atmospheric
pollution and UV light, ETFE has a very long expected
lifespan of more than 20 years. Effective thermal
performance (average U value is 2.6W/m2K for a two-
layer system) and high light transmission (95% visible
light, 85% UV light) enable a range of applications where
traditional materials, such as glass, would not be
practical. It is more than 20 times lighter than glass
(0.35kg/m2 for ETFE vs. 15kg/m2 for glass) and is
ecologically friendly and energy efficient as its constituent
materials are fluorspar, hydrogen sulphate and
trichloromethane, all non petrochemical derivatives. It is
100% recyclable.

16.  These are the least-used materials for fabric structures. Mesh
is a broad term for any porous fabric with open spaces
between its yarns. It can be made from almost any fiber by a
variety of methods, including knitting, weaving and extrusion.
In some cases it acts as a substrate to beef up other fabrics or
is coated to produce specific characteristics.
 For architectural use, meshes typically are available as
polyester weaves lightly coated with vinyl or as knitted fabrics
using high-density polyethylene (HDPE), polypropylene or
acrylic yarns. Polyester mesh dyes well, is strong, has a low
water absorption rate and can be economical. Nylon often is
used in industrial applications because of its strength and
resistance to chemicals, although it does have a high water
absorption rate and may cost more than polyester. Often used
in agriculture, recreation and containment, polypropylene and
HDPE are inert, so they can’t be stained or dyed, and are less
expensive than polyester or nylon. Polypropylene, however,
does have a comparatively low melting rate, a factor in some
industrial applications.

17.  Netting is considered a type of mesh, usually tight
with small holes. Netting finds use in stadium
interiors behind goals, golf ranges and courses,
playground equipment and structures, horticulture,
zoos, construction sites and other areas where
protection or containment is needed.
 Netting consists of a nylon, polyester or
polypropylene with extruded or spun yarns that is
knotted or raschel knitted to form the material. Each
material has its advantages and appropriate
applications. Polyester holds dye better than nylon
but is more expensive; nylon is easier to coat, but
has a higher water absorption rate and doesn’t hold
dye as well. Polypropylene floats on water, is durable
and chemically resistant, but can’t be dyed. Raschel
knitting is a newer, faster manufacturing method
than knotting. One drawback is that the knitted
material can unravel, which can be thwarted by
heat-setting the netting to shrink and stabilize the
fibers.

18.  Films are transparent polymers extruded in sheet form without a
supporting substrate. They are not laminated or coated. Examples
include clear vinyl, polyester or polyethylene. These films are
cheaper than textiles, but they are neither as strong nor as durable.
 Films are much weaker in tension, though more elastic, than scrim-
based fabrics. Films sometimes have application in air-inflated
structures. Air-inflated structures are composed of fabric tubes in
which the air is pressurized, but the structure’s interior itself is not.
Some air-inflated roofs or building envelopes have been made using
two or three layers of films to form air pillows. The film layers are
thermally welded and sealed, and the resulting pillows are inflated
by small fans. The inflation increases the internal pressure to
prestress the surface, creating load resistance. Such film pillows are
framed by an aluminum extrusion perimeter, which must
accommodate some structural movement.
 Films range in thickness from 30 to 200 microns and can be
produced with levels of translucency varying from 25% to 95% light
transmission. Films are low weight, have a life expectancy of 20 to
25 years and highly resist dirt. The inflated pillows exhibit good
thermal insulation values. More research needs to be done to
develop a range of standard reliable, economical details, for
instance, to improve the water seals and reduce wicking.

19.  strip tensile strength
 grab tensile strength
 trapezoidal tear strength
 tongue tear strength
 adhesion strength
 flame resistance
 finished weight
 base fabric weight
 available topcoatings
 resistance to cold cracking
 dead load
 structural properties
 life expectancy

20.  Shading coefficients
 General solar, optical, thermal performance data
 Acoustical data
 Dimensional stability
 Colorfastness
 Cleanability
 Seam strength and stability
 Construction method
 General handling ability, including abrasion
resistance, foldability, etc.