Steel Sheet NZ: Cold Rolled vs Galvanised vs Tread Plate
You need a sheet of steel for a job. Maybe it is a workshop bench top, a trailer floor, a bracket for a gate or a cover for an outdoor box. You search “steel sheet” and find three quite different products: smooth cold rolled sheet, silver galvanised sheet and patterned tread plate. They look similar in a photo, but they behave very differently once they are cut, welded and left outside.
This guide explains what each type is, which thicknesses we stock, roughly what a full sheet weighs and costs, and which jobs each one suits. All prices and sizes come from our steel sheet range as listed online in October 2026.
Steel Sheet Types at a Glance
| Type | Surface | Rust protection | Thicknesses we stock | Sheet sizes | Price per sheet |
|---|---|---|---|---|---|
| Cold rolled mild steel sheet | Smooth, flat, bare steel | None, needs paint or powder coat | 0.8mm to 3mm | 1250 x 2400mm | $104.65 to $389.85 |
| Galvanised steel flat sheet | Smooth with a zinc coating | Z275 zinc coating | 0.6mm to 3mm | 1250 x 2400mm | $78.20 to $389.85 |
| Hot rolled steel tread plate | Raised diamond pattern | None, needs paint or galvanising after fabrication | 3mm to 8mm | 1250 x 2400mm and 1500 x 3000mm | $408.25 to $1,225.90 |
The short version: choose cold rolled sheet when you want a clean surface to paint and the job lives indoors or will be coated. Choose galvanised sheet when the job lives outside and you want rust protection straight off the rack. Choose tread plate when people or vehicles will walk or drive on it.
Cold Rolled Mild Steel Sheet
Cold rolled sheet starts life as hot rolled steel and is then rolled again at room temperature. That second pass gives it a smoother surface and a tighter thickness tolerance than hot rolled material. Our sheet is SPCC grade, a commercial quality cold rolled steel under the Japanese standard JIS G3141.
It bends well, welds easily and takes paint or powder coat evenly, which is why fabricators use it for enclosures, brackets, panels, shelving, furniture frames and workshop jigs. The catch is that it is bare steel. Left unpainted, it will start to rust quickly, especially in a damp garage or anywhere near the coast. Plan to prime and paint it, or send the finished part for powder coating.
- Stocked thicknesses: 0.8mm, 1mm, 1.2mm, 1.6mm, 2mm, 2.5mm and 3mm, all 1250 x 2400mm.
- Price range online: from $104.65 for 0.8mm to $389.85 for 3mm.
- Best for: painted or powder coated parts, indoor fabrication, anything that needs a crisp bend.
See the full cold rolled mild steel sheet range.
Galvanised Steel Flat Sheet
Galvanised sheet is steel sheet coated in zinc. Our flat sheet carries a Z275 coating, listed on the product page as about 20 microns. The zinc protects the steel in two ways: it acts as a barrier, and where it is scratched it corrodes first, which slows rust on the steel underneath.
That makes galvanised sheet the practical choice for outdoor jobs that will not be painted: flashings, ducting, wall and shed patches, cover plates, garden edging, animal shelters and enclosure panels. It still cuts, bends and drills like ordinary sheet. Keep in mind that cut edges and drilled holes expose bare steel, so a dab of zinc rich paint on those areas helps the sheet last.
Welding galvanised sheet needs care. Heated zinc gives off fumes you should not breathe, so grind the coating back around the weld, work with good ventilation and suitable protection, and recoat the weld afterwards. The same steps apply to galvanised tube and box section, which we cover in our steel tube vs steel pipe guide.
- Stocked thicknesses: 0.6mm, 0.75mm, 1mm, 1.2mm, 1.5mm, 2mm, 2.5mm and 3mm, all 1250 x 2400mm.
- Price range online: from $78.20 for 0.6mm to $389.85 for 3mm, with 1.2mm galvanised sheet at $156.40.
- Best for: unpainted outdoor work, flashings and covers, general fabrication where rust is a concern.
See the full galvanised steel sheet range. If you are weighing zinc coated steel against stainless for an outdoor job, our galvanised steel vs stainless steel comparison goes into more detail.
Hot Rolled Steel Tread Plate
Tread plate, also called checker plate or chequer plate, is hot rolled steel with a raised diamond pattern on one face. The pattern gives grip underfoot and under tyres, and the hot rolled steel is tough and easy to weld. Ours is Q235B, a common structural grade under the Chinese standard GB/T 700 with a nominal yield strength of 235 MPa.
It is the usual choice for stair treads, walkways, loading ramps, trailer and ute decks, mezzanine floors and workshop platforms. Like cold rolled sheet, it is bare steel, so it will rust if left as is. Most people paint it after fabrication, or have the finished item hot dip galvanised.
- Stocked in 1250 x 2400mm: 3mm, 4mm, 5mm, 6mm and 8mm.
- Stocked in 1500 x 3000mm: 3mm, 4mm and 6mm.
- Price range online: from $408.25 for 1250 x 2400 x 3mm to $1,225.90 for 1500 x 3000 x 6mm, with the popular 1250 x 2400 x 5mm tread plate at $681.95.
- Best for: anything walked or driven on, where grip and toughness matter more than weight.
Tread plate is heavy. A 1500 x 3000 x 6mm sheet weighs more than 200kg, so plan for a forklift or several people and proper lifting gear. For ramps, floors and anything that carries vehicles or forms part of a structure, have an engineer or your builder confirm the thickness and the support spacing before you order. See the full steel tread plate range.
If weight or rust is the bigger worry, for example on a boat trailer or a ute toolbox, our 5052 aluminium tread plate is about a third of the weight of steel and does not rust.
How to Choose a Thickness
Thickness drives three things: stiffness, weight and price. A thicker sheet spans further without flexing, but it is also harder to cut, bend and carry. The table below shows the approximate weight of one 1250 x 2400mm flat sheet in each stocked thickness, worked out from the nominal thickness and a steel density of 7,850 kg per cubic metre. Actual weights vary slightly with tolerance and coating.
| Thickness | Approx. weight per 1250 x 2400mm sheet | Cold rolled price | Galvanised price | Typical uses |
|---|---|---|---|---|
| 0.6mm | 14 kg | Not stocked | $78.20 | Light flashings, patching, covers |
| 0.75mm | 18 kg | Not stocked | $96.60 | Flashings, ducting, light covers |
| 0.8mm | 19 kg | $104.65 | Not stocked | Light panels, enclosures |
| 1mm | 24 kg | $131.10 | $129.95 | Enclosures, cabinets, folded trims |
| 1.2mm | 28 kg | $156.40 | $156.40 | Brackets, shelving, general fabrication |
| 1.5mm and 1.6mm | 35 to 38 kg | $208.15 (1.6mm) | $195.50 (1.5mm) | Stiffer panels, guards, toolboxes |
| 2mm | 47 kg | $259.90 | $262.20 | Heavier brackets, base plates, workbench tops |
| 2.5mm | 59 kg | $324.30 | $324.30 | Structural brackets, heavier guards |
| 3mm | 71 kg | $389.85 | $389.85 | Heavy duty plates and fabrication |
A few rules of thumb help. Under 1mm suits folding, flashing and covering rather than carrying load. From 1.2mm to 2mm covers most brackets, panels and enclosures a home workshop or small fabricator will make. From 2.5mm upwards, the sheet starts to behave like light plate: stiff, heavy and better cut with a plasma cutter or by a fabrication shop.
Steel Sheet vs Steel Plate
People use “sheet” and “plate” loosely, and there is no single cut-off everyone agrees on. Many suppliers call thinner flat material sheet and thicker material plate, with the changeover somewhere around 3mm to 6mm. Our plain flat steel sheet runs up to 3mm, and our tread plate runs from 3mm to 8mm. If you need a plain, unpatterned steel plate thicker than 3mm, talk to one of our branches about what is available.
Steel Sheet or Aluminium Sheet?
If your job is outdoors, near salt water, or needs to be carried and fitted by one person, compare aluminium before you decide. Aluminium sheet is roughly a third of the weight of steel at the same thickness and forms its own protective oxide layer, while steel is stiffer, stronger for the money and simpler to weld for most workshops. Our aluminium sheet guide covers grades and sizes, and you can browse the full aluminium sheet range online.
Cutting, Handling and Ordering Tips
- Cutting: thin sheet cuts with tin snips, a nibbler or a jigsaw with a metal blade. From about 1.6mm, an angle grinder with a cutting disc or a plasma cutter is quicker. Deburr every edge, as freshly cut steel is sharp.
- Bending: cold rolled and galvanised sheet bend cleanly on a brake press. Thicker tread plate usually needs a fabrication shop with a heavier press.
- Handling: a 2mm sheet is close to 50kg and floppy across its 2.4m length. Use two people, gloves and a flat surface to stop it kinking.
- Storage: keep bare steel dry and off the ground. A light coat of oil or primer stops surface rust on cold rolled sheet while it waits to be used.
- Bulk buys: our product pages list a 20% discount when you buy 10 or more flat sheets, or 5 or more tread plates.
- Getting it home: each product page offers Delivery or Click & Collect, and the shipping calculator shows the delivery cost before you check out.
Steel Sheet FAQs
What size is a standard steel sheet in NZ?
Our cold rolled and galvanised flat sheets are 1250 x 2400mm. Steel tread plate comes in 1250 x 2400mm and the larger 1500 x 3000mm.
Will galvanised steel sheet rust?
The zinc coating protects the steel well in most outdoor settings, but rust can start at cut edges, drilled holes and deep scratches. Seal those with zinc rich paint, and wash the sheet down regularly if it is close to the coast.
Is tread plate the same as checker plate?
Yes. Tread plate, checker plate and chequer plate are names for the same thing: plate with a raised pattern for grip. Ours comes in hot rolled steel and in 5052 aluminium.
Can I paint cold rolled steel sheet?
Yes, and you should. Clean off any oil, prime with a metal primer and top coat, or send the finished part for powder coating. Unpainted cold rolled sheet will rust.
Find the Right Steel Sheet for Your Job
Browse the full steel sheet range online, or see our wider range of galvanised steel sections for the frame that goes with it. If you are not sure which type or thickness suits your project, bring your drawing or measurements to our Albany, Manukau or Christchurch branch and we will help you choose.
