Two quotations can both say “900 GSM tensile fabric” and still describe very different materials. For architects, consultants and procurement teams, the membrane is the most visible part of a tensile structure and one of the biggest influences on its lifespan, appearance and cost. Yet it is often specified with a single number.
This guide explains what GSM actually tells you, how PVC, PVDF-coated and PTFE fabrics differ, what to look for on a fabric data sheet, and how fabric weights have been used on real WhiteShed Solutions projects.
What Does GSM Mean in Tensile Fabric?
GSM stands for grams per square metre. It is the weight of one square metre of coated fabric, including the woven base cloth and its coating. A 900 GSM fabric weighs 900 grams per square metre; a 1050 GSM fabric is heavier.
A heavier fabric generally has a stronger base cloth or a thicker coating, so GSM is a useful first indicator. It is not a complete measure of quality. Two fabrics of the same weight can differ in tensile strength, tear strength, coating chemistry, top coat and manufacturer quality control. That is why GSM should always be read alongside the fabric’s technical data sheet.
The Main Types of Tensile Fabric
PVC-Coated Polyester
The most widely used tensile fabric. A woven polyester base cloth is coated with PVC on both sides, then finished with a protective top coat. It is flexible, weldable, available in many colours and cost-effective, which makes it the usual choice for canopies, car parking shades, pool covers, umbrellas and walkway covers. Its flexibility also suits retractable and demountable structures.
PVC with PVDF Top Coat
The top coat matters as much as the base fabric. A PVDF (polyvinylidene fluoride) top coat improves resistance to UV, dirt pick-up and weathering compared with a basic acrylic lacquer, helping the fabric stay cleaner and look better for longer. For permanent outdoor structures, a PVDF-coated PVC fabric is the typical specification.
PTFE-Coated Glass Fibre
A premium membrane made from woven glass fibre coated with PTFE. It is highly durable, has excellent self-cleaning properties, offers high translucency and is available in non-combustible grades. It is stiffer than PVC and must be handled carefully during fabrication and installation, and it costs significantly more. PTFE is usually specified for large, permanent roofs such as stadiums, airports and landmark projects.
ETFE Foil
A transparent fluoropolymer foil, used as single layers or inflated cushions for skylights, atria and façades where near-glass transparency is needed at a fraction of the weight. It is a specialist system rather than a standard canopy fabric.
HDPE Shade Net
A knitted, breathable shade cloth. It provides sun shade at low cost but is not waterproof, so it is not a substitute for a coated membrane where rain protection is required.
How Long Does Tensile Fabric Last?
Membrane manufacturers and specialist contractors publish design-life guidance that broadly ranks the materials in this order: PVC fabrics with an acrylic lacquer at the lower end (often quoted at around 15 years), PVDF-coated PVC fabrics higher (often 20 years or more), and PTFE-coated glass fibre at the top (often 30 years or more). These are industry guidance figures, not guarantees.
Actual service life depends on UV exposure, pollution, correct tensioning, drainage, and cleaning and inspection. For any project, ask for the manufacturer’s data for the exact fabric being offered and the installer’s warranty terms in writing [confirm WhiteShed warranty terms with the WhiteShed team before publishing].
Beyond GSM: What to Check on the Data Sheet
- Manufacturer and product name: the exact fabric, not just “imported fabric”.
- Tensile strength: usually stated for warp and weft directions in N/5 cm. PVC-polyester fabrics are often grouped into strength types (Type I to Type V).
- Tear strength and coating adhesion: how well the fabric resists tearing and how firmly the coating bonds to the base cloth.
- Top coat: acrylic lacquer or PVDF, and whether it is weldable.
- Light transmission: how much daylight passes through, which affects both brightness and heat.
- Fire performance: whether the fabric is fire retardant (FR) and the standard it has been tested to, with a certificate.
- UV and fungal resistance: important in hot, humid climates.
Fabric Weights Used on WhiteShed Projects
There is no single “correct” GSM. The right fabric depends on span, form, wind exposure, design life and budget. As a reference, these are the fabrics specified on some of our completed projects, all PVDF-coated and fire retardant:
| Project | Structure | Area | Fabric |
|---|---|---|---|
| Malhari Swimming Pool | Arch pool cover | 690 sq ft | 650 GSM, Sioen (Belgium) |
| L&T Infrastructure | Arch structure | 540 sq ft | 750 GSM, Serge Ferrari (France) |
| ICAR, Varsova | Dome structure | Approx. 2,700 sq ft | 900 GSM, Sioen (Belgium) |
| Jindal Maharashtra Seamless | Conical structure | 2,830 sq ft | 900 GSM, Serge Ferrari (France) |
| Hotel Rama International, Aurangabad | Conical structure | Approx. 10,600 sq ft | 1050 GSM, Mehler (Germany) |
Lighter fabrics suited the smaller pool cover and arch, while the largest conical roof used the heaviest fabric. Each selection was made for that project’s span, form and site conditions, and the same weight will not automatically suit a different structure.
Colour, Translucency and Heat
White and light-coloured membranes reflect more sunlight and transmit diffused daylight, which keeps the space underneath brighter and helps limit heat build-up. Darker colours show dirt less but absorb more heat. Where brand colours are needed, discuss colour stability with the fabric manufacturer, since the top coat influences how well colours hold up outdoors.
A Quick Fabric Selection Checklist
- Is the structure permanent, seasonal or retractable?
- What design life does the client expect?
- Is rain protection required, or only shade?
- Does the space need daylight, and how much?
- Are there fire-performance requirements for public use?
- Has the fabric been specified by manufacturer, product, GSM, top coat and FR grade?
When comparing offers from different vendors, use our tensile quotation checklist to make sure the fabric specifications are genuinely comparable. For how fabric choice affects budget, see our tensile structure cost guide.
How WhiteShed Solutions Specifies Fabric
At WhiteShed Solutions LLP, we select the membrane together with the structural form, span and site conditions, rather than as an afterthought. Our project records name the fabric manufacturer, weight, coating and fire-retardant grade for each structure, as the table above shows. Explore our tensile membrane structure services to see how we take a project from design to installation.
FAQs
Is a higher GSM fabric always better?
Not always. A higher GSM usually means a stronger, heavier fabric, but the right choice depends on the span, form and loads. Tensile strength, top coat and manufacturer quality matter as much as weight.
What is the difference between 900 GSM and 1050 GSM fabric?
1050 GSM fabric is heavier and typically has higher tensile strength, which suits larger spans and higher loads. 900 GSM is widely used for medium-sized structures. Check the data sheet rather than relying on weight alone.
Is tensile fabric waterproof?
Coated membranes such as PVC and PTFE fabrics are waterproof. HDPE shade nets are not, as they are designed for shade and airflow.
Is PTFE worth the extra cost?
For large, permanent roofs where long design life, self-cleaning and fire performance are priorities, PTFE is often justified. For most canopies, car parks and pool covers, a good-quality PVDF-coated PVC fabric offers better value.
Specifying a membrane for your project? Request technical information or share your drawings, and our team will recommend fabric options for your span, site and design intent.
