Key Materials That Shape Tensile Structures

By Akram Ansari, Founder, ShadeCo India · Published: 30 May 2026 · Updated: 11 October 2026

The key materials that shape tensile structures are the fabric, the steel frame, the cables, the fittings, the footings and the coatings that protect them. Each one has its own job, and each one affects how the roof looks, how long it lasts and how safe it is. Whether you are planning a car parking shade, an entrance canopy, a shade sail, a walkway cover or a large fabric roof, the right mix of materials matters more than any single part.

A tensile roof may look like just a sheet of fabric on a few poles. In reality, it is a team of materials that share the load. The fabric catches sun, rain and wind. The cables and fittings pass those forces to the steel. The steel carries them down to the footings, and the coatings keep everything from wearing out.

This guide looks at each layer of that team in turn. It explains what each material does, the main choices you have and how the site and the use of the space change the best pick.

Good tensile structure design starts with good material selection. Fabric, steel, cables, coatings and anchors must be chosen according to site exposure, span, wind load, usage, budget and maintenance requirement.

At ShadeCo India Private Limited, our engineers pick the materials, our workshop turns them into finished parts and our installers fix them on site. Because one team handles every step, the fabric, steel and fittings are chosen to work together from the start, not matched up later.

The Six Layers of a Tensile Structure

It helps to think of a tensile structure as six layers, from the sky down to the ground. A weak link in any one of them can let down the whole roof, even if the others are of good quality.

Layer 1: The Fabric or Foil

The fabric is the part everyone sees, and it sets the character of the roof. It decides how much light passes through, whether rain is kept out, how the roof looks after years of sun and how often it needs cleaning. Five main options are used for tensile work.

• PVC-coated polyester: The everyday workhorse of tensile roofs in India. It is waterproof, can be folded and costs less than the other membranes, so it suits most parking shades, canopies and walkways.
• PTFE-coated fiberglass: The long-life choice for big, fixed roofs such as stadiums and large halls. It is pricier and stays fixed in one shape, but it keeps its look and strength for decades.
• ETFE foil: A clear, very light foil that can replace glass. It is picked for atriums and skylights where daylight is the main goal.
• PVC-coated mesh: An open-weave fabric that lets air pass through while cutting much of the sun. It works well for facade screens and some shade sails.
• HDPE shade net: A knitted net for shade only, not rain. It is light, breathable and a good fit for play areas, gardens and open seating.

To compare these fabrics in more depth, see our full roofing materials guide. For clear daylight roofs, see our ETFE membrane structures.

How Fabric Weight Is Chosen

PVC fabric is sold by weight, shown as GSM (grams per square metre). For tensile work it comes in grades from 650 to 1350 GSM. A heavier fabric is stronger and stiffer, but it also costs more and adds a little weight to the frame.

• Small spans: Small canopies, sails and porches often use around 750 to 900 GSM. The forces in the fabric are lower, so a lighter grade does the job well.
• Large spans: Wide roofs over courtyards, sports areas or long parking rows usually need 1050 GSM or heavier. The fabric must carry more pull and stand up to stronger wind.
• Windy or high sites: Hilltops, rooftops and open plains may need a step up in weight, even for a modest span. The engineers decide this after the wind check.

The right GSM is not a guess. It comes from the stress values in the design model, with a safety margin on top.

How Fabric Colour Changes Light and Heat

Fabric colour is not only about looks. It also changes how bright and how warm the space feels below the roof. This is worth thinking about before you pick a shade from the colour card.

• White and light shades: Bounce back much of the sun's heat and allow soft daylight in. The space below feels open and cooler, which suits seating areas, atriums and walkways.
• Dark shades: Give deeper shade and hide dust well, but they soak up more heat. The underside can feel warmer on a hot afternoon, so they suit tall roofs with good airflow.
• Brand colours: Help an entrance canopy or showroom roof match the company look. Bright colours can fade a little over the years, so a PVDF top coat helps keep them fresh.

Good-grade PVC and PVDF fabrics block up to 98% of UV rays, depending on the grade. So even a light, bright fabric gives strong protection from the sun for people and cars below.

Layer 2: Cables

Cables are the quiet workers of a tensile roof. They run along the open, curved edges of the fabric and between masts, holding the shape and carrying pull to the corners. Their size depends on the forces worked out in the design.

• Galvanized wire rope: A common choice for most inland projects. The zinc layer protects the steel wires from rain and damp air.
• Stainless steel wire rope: Used near the sea, around pools and on exposed edges. It costs more but holds up better where salt or chlorine is in the air.
• Edge pockets: The cable often runs inside a welded fabric pocket along the edge. This spreads the pull evenly and gives the edge a neat, smooth curve.

Layer 3: Fittings and Hardware

Fittings join the fabric, cables and steel into one working system. They are small, but they carry large forces, so their material matters as much as their size.

• Stainless steel parts: Turnbuckles, shackles and exposed bolts are often stainless. They do not leave rust stains that could mark a light fabric.
• Galvanized or coated plates: Corner plates and brackets are usually made from steel plate, cut on CNC and then finished. The finish should match the rest of the frame.
• Clamp bars: Used where fabric edges are clamped to a beam or arch. They grip the edge along its full length, so the pull is shared evenly.

Mixing metals needs care. When two different metals touch in damp air, one can corrode faster. Good detailing keeps them apart with washers or sleeves where needed.

Layer 4: The Steel Frame

Steel carries the load from the fabric and cables down to the ground. Columns, masts, arches, beams and brackets are all part of the frame. The frame is designed to IS 800, and its wind loads are worked out using IS 875 (Part 3).

• MS (mild steel): Strong, easy to weld and good value. It must be painted, powder coated or galvanized to protect it from rust outdoors.
• GI (galvanized iron) steel: Comes with a zinc layer already on it, which gives a head start against rust. It is a common pick for parking sheds and walkway frames.
• Pipe or box sections: Round pipes suit masts and curved arches, while box sections suit straight beams and cantilever arms. The shape is picked for both strength and looks.

The steel size comes from the engineering checks, not from habit. Learn how these checks are made in our structural engineering services.

Layer 5: Footings and Anchors

A fabric roof is light, but wind can try to lift it like a kite. So the footings must hold the roof down as firmly as they hold it up. They are designed to IS 456, and the type depends on the ground and the site.

• Isolated concrete footing: The most common base for columns on open ground. Its size is set by the uplift and the soil.
• Anchor bolt foundation: A concrete pedestal with bolts cast in, which the steel base plate bolts onto. The bolt layout is shared with the civil team before they pour.
• Fixing on an existing slab or roof: Used on terraces and rooftops. The slab is checked first to make sure it can take the extra pull.
• Pile: Used where the top soil is weak or loose. It carries the load deeper, to firmer ground.

Layer 6: Coatings and Finishes

Coatings are what keep the other materials looking good and working well over the years. Both the fabric and the steel get their own protection.

• PVDF top coat on fabric: Helps PVC fabric resist UV and lets rain wash off much of the dust. PVDF fabric is backed by a warranty for up to 10 years.
• FR (flame-retardant) grade: Advised for schools, malls, hospitals and other busy public places. It slows the spread of flame across the fabric.
• Primer and paint: A basic, low-cost finish for MS steel in dry inland areas. It needs touch-ups over time.
• Powder coating: Gives a smooth, even colour and a tougher surface than paint. Our workshop applies it in-house.
• Hot-dip galvanizing: The steel is dipped in molten zinc for the strongest rust protection. It is the best pick for coastal, damp or industrial sites.

Matching Materials to the Site

The same roof may need a different material set in a different place. The table below shows how the site changes the usual choices.

This table is a starting point. The final mix also depends on the budget, the design life you want and how easy it is to reach the roof for upkeep.

Matching Materials to the Project

The use of the space matters just as much as the site. Here is how material choices often change from one type of project to another.

• Car parking shades: PVC fabric on a GI or MS frame is the usual mix. Columns near car paths get a tough finish, since they may be bumped. See our parking shade structures.
• Shade sails: HDPE shade net or PVC fabric on steel posts with stainless fittings. HDPE suits play areas where airflow matters, while PVC suits cafes that need rain cover. See our HDPE shade sails.
• Entrance canopies: PVC with a PVDF top coat, often in a brand colour, on a powder-coated frame. The look matters here, so the finish is chosen with care.
• Atriums and skylights: ETFE foil or a light-coloured PVC or PTFE fabric. These let soft daylight into the space below.
• Stadiums and large halls: PTFE-coated fiberglass or heavy PVC on a galvanized frame. These roofs are built to last for decades, so long-life materials pay off.

How Materials Are Checked Before Use

Good materials only help if they reach the site in good shape. Our workshop checks each batch before it is cut or welded.

• Fabric rolls: Checked for grade, colour, coating and any flaws before cutting. Panels are then cut on a CNC fabric cutter or by hand and joined by HF or hot-air welding.
• Steel: Checked for size and thickness against the drawings. Plates and brackets are cut on CNC, so holes line up on site.
• Finishes: Powder coat and paint are checked for even cover. Galvanized parts are checked when they return from the outside plant.

See how this work is done in our manufacturing services.

Common Material Mistakes to Avoid

• Choosing fabric on price alone: A cheap, thin fabric may look fine on day one but fade or sag early. The right grade usually costs less over the life of the roof.
• Plain paint near the sea: Salt air eats into painted MS steel fast. Coastal sites need galvanizing and stainless hardware.
• Mixing metals carelessly: Different metals in contact can rust each other. Simple washers or sleeves prevent this.
• Ignoring fire grade: Busy public spaces should use FR fabric. It is much easier to choose it at the start than to replace the fabric later.
• Using shade net where rain cover is needed: HDPE is great for shade but lets rain through. If rain cover matters, choose PVC fabric.

How Care Affects Material Life

Every material lasts longer with a little care. Fabric stays brighter when dust and leaves are washed off. Cables and fittings stay safe when they are checked and tightened. Steel lasts longer when small scratches in the coating are touched up before rust spreads.

With the right materials and regular checks, a well-built tensile structure can give a structural life of 25 to 30 years. Learn more about our cleaning and maintenance services.

FAQ

Frequently Asked Questions

Common questions about the fabric, steel, cables, footings and coatings used in tensile structures.

What are the main materials in a tensile structure?

Every tensile structure has six main material groups. The fabric or foil gives shade and rain cover. Cables hold the fabric edges, and fittings such as plates and turnbuckles join everything together. The steel frame carries the loads, the footings hold the roof down against wind, and coatings protect the fabric and steel from sun, dirt and rust. All six must suit the site and work as one set.

What GSM fabric is used for a tensile structure?

PVC fabric for tensile work comes in grades from 650 to 1350 GSM. Small canopies, porches and sails often use around 750 to 900 GSM, because the forces in the fabric are lower. Wide roofs over courtyards, sports areas or long parking rows usually need 1050 GSM or heavier. Windy hilltops and rooftops may need a heavier grade even for a small span. The final choice comes from the design checks.

What is the best steel finish for a tensile frame?

The best steel finish depends on the site. In dry city and inland areas, primer and paint or powder coating works well and gives a clean colour. Near the sea, around pools or in factories, hot-dip galvanizing is the better pick, often with paint on top for looks. Galvanized steel resists rust far longer in salty or damp air. Powder coating also gives a tougher surface than plain paint.

Should tensile fittings be stainless steel or galvanized?

Both work, and the choice depends on where the roof is. Galvanized fittings are a good, lower-cost choice for most inland sites. Stainless steel fittings are better near the sea, around swimming pools and in damp areas, because they resist salt and chlorine. Stainless parts also avoid rust stains on light fabric. When different metals touch, washers or sleeves are used so one metal does not corrode the other.

Do I need fire-retardant fabric for my tensile roof?

Fire-retardant (FR) fabric is advised for busy public spaces such as schools, malls, hospitals, hotels and event areas. It slows the spread of flame across the fabric, which gives people more time to move away safely. Some building rules or clients may also ask for it. It is much easier to choose an FR grade at the start than to replace the fabric later, so discuss it during design.

What foundation does a tensile structure need?

The foundation depends on the ground and the site. Most columns on open ground sit on an isolated concrete footing, often with anchor bolts cast into a pedestal. On terraces and rooftops, the frame can be fixed to the existing slab after it is checked. Where the top soil is weak, piles carry the load deeper. In every case, the footing must resist wind uplift as well as carry the roof.

Can I use HDPE shade net for a car parking shade?

You can use HDPE shade net for a car parking shade if you only need sun cover. It blocks much of the sun, lets air flow and costs less than PVC fabric. But HDPE does not keep out rain, so cars will still get wet in the monsoon. If you want rain cover as well, PVC-coated polyester fabric is the better choice for a parking shade.

How long do tensile structure materials last?

Life varies by material and care. With the right materials and regular upkeep, a well-built tensile structure can give a structural life of 25 to 30 years. PVDF-topped PVC fabric is covered by a warranty for up to 10 years, while PTFE fabric lasts much longer. Steel lasts longest when its coating is kept in good shape, and cables and fittings stay safe with regular checks.

Which Materials Are Right for Your Tensile Structure?

The right materials are the ones that suit your site, your use and your budget together. For most parking shades and canopies, PVDF-topped PVC fabric on a coated steel frame is a sound choice. Coastal and industrial sites need stronger rust protection, and landmark roofs may call for PTFE or ETFE. In every case, the fabric, cables, fittings, frame, footings and coatings should be chosen as one set.

To learn how these choices fit into the wider planning of a roof, read our guide to the design process of tensile structures. If you need help choosing the right fabric, frame and finish for your project, contact ShadeCo India for design advice and a quotation.