Decramastic Roof Guide NZ: Lifespan, Asbestos, Replacement

Quick answerA decramastic roof is made of pressed steel tiles with a bitumen-based coating and a stone chip finish. It fails gradually: the chip washes off, the coating breaks down and the steel rusts. WorkSafe warns that decramastic installed before asbestos was phased out may contain asbestos, so get the tiles tested before any cleaning, painting or removal. A worn-out decramastic roof is usually best replaced with steel.

Older pressed metal tile roof due for replacement

Decramastic tiles gave a lot of New Zealand homes the look of a tiled roof without the weight. Many of those roofs are now old, and owners face the same choice: repair, paint, or replace. The answer depends on two things you can check, how much chip and coating is left, and whether the tiles contain asbestos.

This owner's guide explains what decramastic is, how it ages, what WorkSafe says about asbestos, when painting and repairs are worth it, and what affects the cost of decramastic roof replacement. It is written for anyone with an older home and a roof that is starting to shed grit into the spouting.

What is a decramastic roof?

Decramastic is a pressed steel roofing tile, shaped to look like a row of tiles, with a bitumen-based coating and a surface of stone chips bonded on top. The tiles are nailed to timber battens and overlap one another, so the roof is light but has many joints and fixings.

Under the Building Code's Acceptable Solution E2/AS1, pressed metal tiles need a minimum pitch of 12 degrees for standard profiles and 15 degrees for shingle or shake profiles, and every metal tile roof must have underlay. Those rules apply to new metal tile roofs; older decramastic was laid to the practice of its day, and many roofs have tired underlay or none at all.

How long does a decramastic roof last?

There is no fixed lifespan. The Building Code sets a minimum of 15 years for roof cladding, and many decramastic roofs have lasted far longer, but most of those still in service are now old enough that the coating is failing.

They age in a recognisable order. The stone chip loosens and washes into the spouting, first on the faces that get the most sun and weather. Once the chip is gone the bitumen coating breaks down, and then the steel underneath starts to rust, often from the hidden underside first. Leaks follow at tile overlaps, nail holes, valleys and around flues. Foot traffic speeds this up, because walking on the tiles cracks the coating and dents the steel.

Moss and lichen hold moisture against the tiles, and salt does the same on coastal sites. Homes near the water in Howick and Pakuranga, exposed to the Tāmaki Strait, tend to see corrosion sooner than inland houses.

Piles of stone chip in the spouting or at the foot of downpipes
Bare black or rust-coloured patches where chip used to be
Rust spots on the underside of the tiles, visible from the roof space
Cracked, lifted or dented tiles along walking routes
Leaks at valleys, ridges and flues

Do decramastic tiles contain asbestos?

Some do, and you cannot tell by looking. WorkSafe's August 2026 safety alert states that decramastic roofing installed before asbestos was phased out may contain asbestos, and describes a 1970s house where decramastic tiles were water blasted, debris spread across the property and inside the home, and testing confirmed chrysotile asbestos.

The only way to know is to have a sample taken by a competent person and tested by an IANZ-accredited laboratory, which WorkSafe names as a way to confirm it. In suburbs where much of the housing dates from the 1960s to the 1980s, such as Glenfield, Pakuranga and Howick, the roof is old enough that testing should come before any work. If the result is positive, our asbestos testing and removal process follows WorkSafe's licensing and notification rules.

Is your decramastic roof worth saving?

Cheeky's Roofers arranges a tile test, checks the roof space and prices repair, paint and replacement side by side.

0800 766 342 Book Online Get a quote

Can you paint a decramastic roof?

Yes, if the tiles are sound and the preparation is safe. Paint can refresh a roof that still has most of its chip and no rust through, but it will not rebuild a coating that has already failed.

Preparation is where people get caught. High-pressure water spraying, which WorkSafe defines as over 350 kPa or 50 psi, must not be used on asbestos-containing material, and WorkSafe can issue infringement fees of up to $9,000, with fines of up to $30,000 on conviction. WorkSafe recommends a soft wash or chemical wash instead. So test first, then clean with a method that suits the result.

If the roof passes both tests, sound tiles and a clear or safely managed asbestos result, roof painting can buy useful years. If chip loss and rust are widespread, the paint has nothing solid to hold on to and the money is better put towards replacement.

Can decramastic tiles be repaired?

Yes, in small areas. A few cracked or dented tiles, a lifted edge or a leaking valley can be repaired when the rest of the roof is sound, and that is often the right call after a storm or a careless trade has walked across it.

Repairs stop making sense when the problem is everywhere at once. Matching old tiles is difficult, replacement tiles stand out against weathered ones, and every visit risks more damage from foot traffic. If you are calling someone out for the third time in a few winters, it is time to price a replacement alongside the repair. Our tile roof repairs service covers the small jobs, and we will tell you honestly when a repair is only buying a season.

How much does it cost to replace a decramastic roof?

The Made 4 Tradies rates guide, updated September 2026, puts decramastic tile replacement at $95 to $150 per square metre. The biggest variable on any one house is the asbestos test result: a clear result means a normal strip and re-roof, while a positive result adds licensed removal, a five-day notice to WorkSafe and controlled disposal.

After that, the price follows the roof: area, pitch, hips and valleys, access, and the steel grade your site needs. Decramastic is nailed to battens, so the battens come off and purlins go on for the new steel roof, and new underlay goes down. Because decramastic and longrun steel are both lightweight, the change in load on the frame is small, unlike a conversion from concrete tiles.

Repair, paint or replace: how do you decide?

Decide on condition, not age. The table sums up the usual answer for each situation, assuming the asbestos question has been answered first.

Cheeky's Roofers starts every decramastic job with a tile test and a look in the roof space, then prices the options side by side so you can compare repair, paint and replace on the same page. For owners in Howick and the eastern suburbs we also check the exposure zone before choosing the steel. If your roof is shedding chip, book a free measure and we will tell you which column you are in. Cheeky's Roofers shows removal and roofing as separate lines, so you can see exactly what the asbestos result changes.

What you see	Usual answer
Chip mostly intact, no rust, a few damaged tiles	Repair the damaged tiles
Chip thinning evenly, no rust through, sound underlay	Test, soft wash and paint
Bare patches, rust spots, leaks in more than one place	Replace with longrun steel
Rust visible from the roof space, brittle or missing underlay	Replace with longrun steel

Frequently Asked Questions

Why is there black grit in my spouting?

That is stone chip coming off decramastic tiles. A little is normal on an older roof, but heavy build-up means the coating underneath is being exposed and will wear faster. Do not hose or water blast the grit off the roof until the tiles have been tested for asbestos.

Can I walk on a decramastic roof?

It is best avoided. Walking on the tiles can crack the coating and dent the steel, which starts rust and leaks, and a roof that may contain asbestos should not be disturbed. Leave access to a roofer with the right gear and testing in place.

Can a new roof go over the top of decramastic?

Overlay systems exist, but BRANZ lists roofing laid directly over an older roof among the situations that need building consent, and an overlay hides the condition of the battens and underlay. Removing the tiles lets the timber be checked and the new roof be fixed properly.

Is decramastic the same as a metal tile roof?

Decramastic is one type of pressed metal tile, the older stone-chip style with a bitumen coating. Modern pressed metal tiles use different coatings, and E2/AS1 treats them all as metal tiles with the same minimum pitch and underlay rules.

How long does decramastic replacement take?

About the same as a standard re-roof once the tiles are off. If the test shows asbestos, allow extra time for the licensed removalist and the five days' written notice WorkSafe requires before removal starts.