GI sheet and GI coil are galvanized steel: mild steel that has been coated with zinc on a continuous line. In the UAE it goes into ducting, roofing, cladding, cable trays, partitions and a thousand fabricated parts. Most of the confusion when ordering comes from two things, the gauge system and the zinc coating class. This guide covers both, with the weight figures you need to price a job.
Gauge to millimetres
Gauge is an old system where a bigger number means thinner steel. Sheet is still ordered by gauge across the UAE, particularly in HVAC. These are the common sizes and the thickness each one refers to in practice.
| Gauge | Thickness (mm) | kg per m² | kg per 4 x 8 ft sheet | kg per 1.5 x 3 m sheet |
|---|---|---|---|---|
| 16 | 1.60 | 12.56 | 37.3 | 56.5 |
| 18 | 1.20 | 9.42 | 28.0 | 42.4 |
| 20 | 0.90 | 7.06 | 21.0 | 31.8 |
| 22 | 0.70 | 5.49 | 16.3 | 24.7 |
| 24 | 0.55 | 4.32 | 12.8 | 19.4 |
| 26 | 0.45 | 3.53 | 10.5 | 15.9 |
| 28 | 0.38 | 2.98 | 8.9 | 13.4 |
Two warnings. First, gauge numbers vary slightly between standards, so a 24 gauge sheet can be 0.55 or 0.61 mm depending on who made it. Always order in millimetres if the thickness matters. Second, the quoted thickness may be base metal thickness (BMT) or total coated thickness (TCT), and they differ by the zinc. On thin gauges that difference is real money.
Base metal or total coated thickness
A Z275 coating adds about 0.04 mm across both faces. On a 0.45 mm sheet that is nearly ten per cent of the thickness. If one supplier quotes 0.45 BMT and another quotes 0.45 TCT, the second is selling you less steel. Ask which basis the quote uses, and put the answer on the purchase order.
Zinc coating classes
The Z number is the total zinc on both faces in grams per square metre. Z120 is 120 g/m², Z275 is 275 g/m². Heavier zinc lasts longer, particularly in coastal air.
| Class | Zinc, both faces | Typical use in the UAE |
|---|---|---|
| Z100 to Z120 | 100 to 120 g/m² | Internal ducting, partitions, indoor fabrication |
| Z180 | 180 g/m² | General purpose, semi exposed work |
| Z275 | 275 g/m² | Roofing, cladding and anything outdoors |
| Z350 and above | 350 g/m² and up | Coastal and industrial exposure |
Our full guide to GI coating classes covers the American G90 equivalents and how to check what you actually received.
Coil, sheet or slit strip
- Full coil for roll forming lines, purlin machines and tube mills. Widths are commonly 1000, 1219, 1250 and 1500 mm.
- Slit coil cut to your strip width, for profiling and section lines.
- Cut to length sheet in standard sizes such as 1219 x 2438 mm and 1.5 x 3 m, or to your dimensions.
Cut to length from coil is usually cheaper than buying standard sheets and trimming them, once the quantity is reasonable. Send the finished sizes you need and the answer becomes obvious quickly.
Which thickness for which job
- Ducting: 24 to 26 gauge for low pressure, 22 gauge and heavier for larger sections and higher pressure.
- Roofing and cladding sheets: 0.45 to 0.70 mm, usually pre-painted.
- Cable tray and trunking: 1.0 to 2.0 mm depending on span and load.
- Partitions, framing and furniture: 0.5 to 1.2 mm.
- Fabricated brackets and enclosures: 1.2 mm and up.
GI, PPGI and galvalume
GI is zinc coated steel. PPGI is the same material with a paint system applied on the line, used for roofing and cladding where colour matters. Galvalume, an aluminium zinc alloy coating, holds up better against heat and some corrosive environments and is common on roof sheets. Tell us the application and the exposure and we will say which one actually suits, rather than just quoting what is easiest to source.
What drives the price per ton
Four things: the base steel price, the zinc class, the width, and the thickness. Thin gauges cost more per ton than thick ones because the mill runs slower and the coil yields fewer tons per hour. Non standard widths mean slitting and scrap. A heavier zinc class adds cost roughly in line with the extra zinc. Quantity matters too, since a full coil prices better than a few sheets cut from one.
What to send for a quote
- Thickness in mm, and whether that is base metal or total coated
- Zinc coating class, or the exposure if you want it specified
- Width, and coil or cut to length with sheet sizes
- Plain GI, PPGI with a colour reference, or galvalume
- Tonnage and delivery location
Frequently asked questions
What is the weight of a 24 gauge GI sheet?
About 4.32 kg per square metre, so roughly 12.8 kg for a 4 x 8 ft sheet, before the zinc is counted.
What thickness is 22 gauge?
About 0.70 mm. Order in millimetres where tolerance matters, because gauge tables vary.
What is the difference between GI and PPGI?
PPGI is galvanized steel with a factory applied paint system. The steel underneath is the same.
Which zinc class do I need near the coast?
Z275 or heavier for anything exposed. Z120 to Z180 is fine for internal work such as ducting and partitions.
Do you supply mill test certificates?
Yes, MTCs are issued with the material.
Getting a price
Send your requirement through the steel quote request form or on WhatsApp at +971 56 227 5722. Full details of what we supply are on the GI coil and sheet page, and for hot rolled material see hot rolled coil. Deliveries go to all seven emirates.
For the full range of sections we supply, with sizes, grades and standards, see all steel products we supply in the UAE.