Ask three suppliers for a quote on iron sheets and you will get three numbers that look nothing alike. One quotes per square metre. Another quotes per tonne. The third quotes per sheet and forgets to mention the gauge.

None of them is necessarily cheating you. They are just describing different products using the same loose word. This guide sorts out what the word actually covers, what separates one type from another, and what each one should cost.

What people mean by iron sheets

Strictly speaking, almost nothing sold today as an "iron sheet" is iron. It is steel — usually low-carbon steel — that has been rolled flat and given a protective coating.

The name stuck for historical reasons, and it varies by region. <cite index="44-1">In many markets, the terms iron sheets, tin sheets, and GI sheets all refer to galvanized steel roofing sheets, though the underlying classification by coating, thickness, and profile stays the same.</cite>

That distinction matters commercially. When you compare quotes, you are not comparing "iron" against "steel". You are comparing three variables:

• The substrate — the base steel and its strength.
• The coating — what protects it, and how much of it there is.
• The profile — flat, corrugated, ribbed, or tile-shaped.

Get those three right and price comparison becomes straightforward. Get them wrong and you are comparing a warehouse roof to a garden shed.

The main types of iron sheets

Galvanized iron sheets (GI)

The baseline product. Steel sheet dipped in molten zinc, which bonds to the surface and corrodes sacrificially in place of the steel underneath.

Where it is used: industrial roofing, warehouse cladding, fencing, agricultural sheds, silos.

Coating classes: specified either by mass (Z80, Z120, Z275 grams per square metre, both sides combined) or by the American system (G60, G90). Higher number, thicker zinc, longer life. <cite index="43-1">The governing standard is ASTM A653, which covers zinc-coated and zinc-iron alloy-coated steel sheet made by the hot-dip process.</cite>

The single most common buying mistake: comparing two GI quotes on thickness alone while ignoring coating class. A 0.45 mm sheet with Z80 coating and a 0.45 mm sheet with Z275 coating are the same thickness and radically different products. The second will outlast the first by years in the same environment.

Corrugated iron sheets (CGI)

Not a different material — a different shape. The wave profile is a structural trick: bending the sheet into ridges dramatically increases its stiffness across the span without adding any weight.

That is why a sheet you could bend with your hands when flat will carry a person's weight once corrugated and properly supported.

Thickness guidance matters more than most buyers realise. <cite index="38-1">Relief-sector specifications note that 0.475 mm (28 gauge) suits shelters where wind speed stays below 250 km/h with purlin spacing of 0.50 m maximum, while 0.4 mm (30 gauge) suits wind speeds below 200 km/h with spacing up to 0.60 m.</cite>

A note on ordering: always specify thickness in millimetres, never in gauge. Gauge conversion differs between materials and profiles, and the ambiguity has caused more disputed deliveries than any other single factor in this product category.

Colour-coated sheets (PPGI and PPGL)

Galvanized or galvalume sheet with a factory-applied paint system baked onto the surface.

PPGI = pre-painted galvanized iron. PPGL = pre-painted galvalume.

The paint does two jobs: it adds a second barrier over the metallic coating, and it gives you colour choice. Paint systems vary in quality — polyester is the economy option, while fluoropolymer systems (PVDF) hold colour far longer and cost accordingly.

Where it is used: commercial and retail buildings, showrooms, villas, anywhere appearance matters.

Galvalume sheets (AZ)

Coated with an aluminium-zinc alloy rather than pure zinc. <cite index="46-1">The typical composition is around 55% aluminium, 43.4% zinc and 1.6% silicon, which delivers strong corrosion resistance, good heat tolerance and high thermal reflectivity.</cite>

Where it earns its premium: hot climates and coastal exposure. The aluminium component resists atmospheric corrosion better than zinc alone, and the reflectivity reduces heat transfer into the building below — a real operating-cost factor in Gulf conditions.

Where it does not: it performs poorly in direct contact with wet concrete or unprotected alkaline surfaces. Detail the junctions properly.

Tile-profile sheets

Pressed to imitate clay or concrete roof tiles while keeping the weight and installation speed of steel.

Trade-off: more expensive per square metre than plain corrugated, and slightly more wasteful to cut around complex roof geometry. Chosen for appearance, not economy.

Types of iron sheets and their prices compared

Prices below are indicative ranges compiled from international supplier listings and market guides current to early-to-mid 2026. They exclude freight, duties and local taxes.

*Service life for zinc-coated products depends heavily on coating class and environment. The same sheet may last 25 years inland and under 10 years in coastal spray.

<cite index="41-1">As a US market reference point, average corrugated metal sheet cost in 2025 ranged between $1.50 and $4.00 per square foot depending on material and gauge.</cite>

Why the ranges are so wide

Six variables move the number, and a quote that does not state them is not a quote:

• Thickness. The dominant cost driver. Sheets are made from coil, and coil is sold by weight.
• Coating class. Zinc is a traded commodity. Z275 costs meaningfully more than Z80.
• Paint system. Polyester versus PVDF can shift the price by a third.
• Order volume. Most mills set minimum order quantities in tonnes, often 1 to 25 tonnes. Below MOQ you buy from a stockist at a markup.
• Sheet dimensions. Custom lengths reduce site waste but cost more per metre.
• Freight. For a low-density product like sheeting, shipping can be a large share of landed cost.

The per-square-metre trap

A supplier quoting per tonne and a supplier quoting per square metre are not directly comparable until you convert.

Rough conversion for flat sheet:

Weight per m² (kg) = thickness (mm) × 7.85

A 0.45 mm sheet weighs about 3.53 kg per square metre. So one tonne yields roughly 283 square metres of flat sheet — before you subtract the overlap consumed by the corrugation profile and the lap joints, which together can absorb 10–15% of your nominal area.

Buy by tonne, budget by covered area, and add the overlap allowance. Skipping that step is how projects end up ordering short.

Choosing the right sheet for the job

Match the coating to the environment

This is the decision that determines whether your roof lasts eight years or thirty.

• Inland, dry, low pollution: standard GI with moderate coating class is adequate.
• Coastal or high humidity: galvalume or heavy-gauge GI (Z275 and above). Salt spray accelerates zinc consumption sharply.
• High heat and strong sun: galvalume, or PPGL with a reflective topcoat.
• Agricultural buildings: heavier coating than you would think. Animal waste generates ammonia, which attacks zinc.
• Industrial areas with acidic fallout: colour-coated over heavy galvanizing, and plan for inspection cycles.

Match the thickness to the span

Thickness and purlin spacing are one decision, not two. A thinner sheet on closer supports can outperform a thicker sheet on wide supports, and often costs less overall once you count the steelwork.

Ask your supplier for the load-span table for the specific profile you are buying. If they cannot produce one, that tells you something about the product.

Do not mix metals carelessly

Fixing galvanized sheet with copper or brass fasteners sets up a galvanic cell that eats the zinc around every screw. Use fasteners matched to the sheet — and use the washers supplied with them.

The same principle applies to the substructure. Aluminium sheeting on a bare steel purlin will corrode at every contact point unless the junction is isolated.

Iron sheets versus reinforcing steel

These two products get confused constantly in search, and they solve completely different problems.

A building uses both, in different places, for different reasons. The sheet keeps the weather out. The rebar keeps the structure standing.

If your project needs the second, ALSSAD STEEL manufactures reinforcing steel bars to SASO ASTM 615 Grade 60, alongside smooth round bar steel for stirrups and forming work. Our full range is on the products page, and our guide to reinforcing steel covers types, specifications and sizing.

Storage and handling

More sheeting is ruined in the stockyard than on the roof.

Wet storage staining — the white powdery deposit you see on galvanized sheets — happens when bundles trap moisture between sheets with no airflow. The zinc oxidises rapidly in the confined damp, consuming coating life before the sheet is ever installed.

Practical rules:

• Store off the ground on timber bearers, sloped for drainage.
• Never leave bundles wrapped in plastic outdoors. Condensation forms inside and cannot escape.
• Separate sheets if storing long term, or at minimum tilt the stack.
• Lift, do not drag. Dragging one sheet across another scores the coating and creates a corrosion start point.
• Cut with shears or a metal-cutting blade, never an abrasive disc. Abrasive cutting burns the coating back from the cut edge and throws hot particles that embed in adjacent sheets.
• Treat every cut edge with a zinc-rich primer on exposed applications.

That last point gets skipped constantly. Every cut you make on site removes the factory protection at that edge, and the edge is where corrosion starts.

Frequently asked questions

What are the main types of iron sheets?

The five main categories are galvanized (GI), colour-coated (PPGI/PPGL), galvalume, corrugated, and tile-profile sheets. They differ by coating type, thickness and profile shape, and each suits different environments and budgets.

How much do iron sheets cost?

Indicative ranges in 2026 run roughly $550–$780 per tonne for plain galvanized sheet, $5–$10 per square metre for corrugated galvanized, and $7–$12 per square metre for colour-coated. Thickness, coating class, paint system and order volume all move the figure significantly.

Which iron sheet lasts longest?

Galvalume generally outlasts standard galvanized in hot and coastal conditions thanks to its aluminium-zinc coating. But coating class matters more than coating type — a heavily galvanized sheet will outlast a thinly coated galvalume sheet in most settings.

What thickness should I choose?

It depends on span, wind exposure and load. For general roofing, 0.40–0.50 mm is common, with 0.55 mm and above for wider purlin spacing or higher wind loads. Always request the load-span table for the specific profile.

Are iron sheets and galvanized sheets the same thing?

In everyday usage, yes. "Iron sheet" and "tin sheet" are regional names for what is technically zinc-coated steel sheet. The material is steel, not iron.

Does ALSSAD STEEL supply iron sheets?

No. ALSSAD STEEL manufactures reinforcing steel bars and smooth round bar steel for construction and industrial applications. This guide is published as a technical reference for the construction sector.

Before you order

Three things to settle before you sign anything:

Specify in millimetres and coating class, not gauge and adjectives. "0.45 mm, Z275, ASTM A653" is a specification. "Heavy duty galvanized" is a sales phrase.

Convert every quote to the same unit before comparing, and add your overlap allowance to the area calculation.

Match the coating to your actual environment, not to the cheapest line on the quote. The saving on a lighter coating disappears the first time you re-roof.

For reinforcing steel supplied direct from the mill with full certification, request a quote or contact our team. You can also review our quality certifications.