What COLORSTEEL actually is
NZ Steel says COLORSTEEL starts as ZINCALUME coated steel, which is then pre-treated, primed and painted. Independent rollformers shape it into corrugate, trapezoidal and tray longrun profiles.
The name gets used loosely for any coloured steel. NZ Steel says genuine sheets have COLORSTEEL printed on the back, and suggests having it named in the quote and asking for a copy of the warranty.
MAXAM or ALTIMATE?
| COLORSTEEL MAXAM | COLORSTEEL ALTIMATE | |
|---|---|---|
| What it's made of | Steel with a magnesium-enhanced aluminium and zinc coating, 0.40 or 0.55 mm thick | Marine-grade aluminium, 0.90 mm thick, with no metallic coating |
| Where NZ Steel aims it | Most of New Zealand, from alpine areas to city centres and much of the coast | Extremely severe marine and breaking surf sites, plus volcanic and highly corrosive spots |
| Right beside breaking surf (Extremely Severe) | Not recommended | Warranted |
| Roofing perforation warranty, Mild to Very Severe | 50, 40, 30 and 20 years | 50, 40, 30 and 30 years, and 25 in Extremely Severe |
| Roofing paint warranty | 18 years in Mild and Moderate, 15 in Severe and Very Severe | 18 years in Mild and Moderate, 15 in the harsher three |
Coast, geothermal, wind and snow
NZ Steel's five categories run from Mild to Extremely Severe, set by distance from the coast, with different distances for the east and west coasts. Mild typically starts 5 km from breaking surf or more than 1 km from calm saltwater, and covers most of the country. Within 100 metres of any saltwater, NZ Steel asks you to contact it to confirm the warranty.
Your council may talk about NZS 3604 exposure zones instead. They're a separate system with different boundaries, so don't read one off the other: ask your roofer to check both for your address.
Geothermal ground is less clear-cut. NZ Steel's FAQ points to ALTIMATE there, while its MAXAM launch article says MAXAM copes too. In Rotorua, around Taupō or near any fumarole, get the product and warranty confirmed by NZ Steel in writing.
Wind and snow come down to the profile, fixings and spouting more than the paint. NZ Steel also notes that after the Christchurch earthquakes, experts strongly recommended lightweight metal roofing over heavy tiles.
How long it lasts, and the small print
The perforation warranty covers corrosion right through the sheet; the paint warranty covers flaking, peeling and excessive fading. It runs from the day the material reaches site, covers the COLORSTEEL only, and needs the maintenance programme followed and documented.
NZ Steel excludes damage from swarf (filings from cutting and drilling) left on the roof, run-off from lead or copper, ponding, end-lapped sheets, and storms and earthquakes. A little white corrosion at unwashed bends or cut edges is normal weathering, it says, not a fault.
Looking after it
Rain washes the open roof. The work is in the spots it misses: soffits, spouting (gutter) undersides, and under aerials and solar panels. NZ Steel wants those hand-washed every 6 months in Mild and Moderate sites, every 3 months in Severe, and monthly in Very Severe and Extremely Severe, with water and a soft brush.
Leave small scratches alone; NZ Steel doesn't recommend touch-up paint at all. Lichen is harder, since NZ Steel says scrubbing it off damages the paint, so its weak bleach wash is a job for a roofer. Painting later is possible, but the warranty won't cover failures caused by the new paint. See roof paint.
What makes a COLORSTEEL job bigger or smaller
Distance to the sea decides the product, and ALTIMATE needs aluminium or grade 304 stainless fixings plus room for the sheets to expand. Then it's the roof's size and pitch, the valleys, chimneys and skylights to flash, and whether old decramastic tiles need an asbestos test before they come off. E2/AS1 requires underlay under profiled metal longrun, so that belongs in the quote too.
Before you say yes
- Is it genuine COLORSTEEL, and MAXAM or ALTIMATE?
- Which NZ Steel category is my address in, and have you checked the warranty for it?
- Will lead flashings be swapped for zinc or aluminium, and swarf cleared every day?
- Will I get the warranty and maintenance schedule in writing?
What you can do, and what's the roofer's
You can
- Hose soffits and spouting undersides you can reach from the ground
- Keep a note of washing dates for the warranty
- Point out copper pipes or lead flashings that drain onto the roof
Leave to a roofer
- Washing the roof itself, and lichen treatment
- Replacing corroded fasteners
- Flashings, sheets and anything through the roof
What we'd choose
For most New Zealand homes, MAXAM is the straightforward pick. If you can hear the surf from the deck or live beside steaming ground, we wouldn't guess: we'd have the roofer get NZ Steel to confirm the product for your exact address before you sign. Then put the washing dates in your calendar, because that's what keeps the warranty alive.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.