What a decramastic roof actually is
Decramastic is a pressed steel tile with a stone-chip coating, a thin profiled metal tile, painted and then finished with a layer of crushed-stone granules bonded on top. It was hugely popular in New Zealand from roughly the 1960s through the 1980s, so it's common on Wellington and Hutt Valley homes of that era. You'll also hear it called pressed-metal tile, stone-chip tile, or by various brand names. Whatever the name, the way they age, and the way they leak, is much the same.
For its time it was a clever product: light, earthquake-friendly, and cheaper than concrete or clay tile. The catch is that most of these roofs are now 40 to 50 years old or more, and a good number are at or near the end of their serviceable life.
Why decramastic roofs leak
These roofs rarely leak through the middle of a sound tile. The trouble almost always starts at the details and the edges:
- Rust on the tile toes and cut edges. The exposed front lip of each tile and any cut edge is where rust takes hold first. Once the steel is compromised, the tile stops doing its job.
- Ridges, hips, valleys and dormers. The capping and the junctions are the usual leak points, especially after wind-driven rain, far more often than the open field of the roof.
- Lost stone chips. As the coating ages the granules shed, leaving bald, shiny patches. That's a sign the protective system is breaking down and the steel underneath is more exposed.
- Tired or perished fixings. The original nails or clips loosen and rust over decades, and a lifted tile is an entry point.
- Previous patch repairs. We very often find earlier fixes that were never going to last: smears of silicone, mismatched screws, soft-edge flashings. They sometimes make the next leak harder to trace.
Phrasings you may have seen in a building report or earlier quote:
"Rust to tile toes / cut edges."
"Stone-chip loss, coating breaking down."
"Previous repairs noted, silicone to ridge / flashings."
"Roof at or near end of serviceable life."
If these sound familiar, this guide is written for exactly your situation.
Getting a proper look at the parts that leak
Those details are what a quick look from the ground or a ladder tends to miss: the ridges, hips, valleys, dormers and tile toes. It's a big part of why a building inspector will often mark the roof "not accessed" and leave the question open.
What matters is close-up detail on them and on the overall condition of the roof. Where a roof is steep, high, or hard to reach, the drone captures that view. The point is a detailed, plain-language read, not a guess from the ground.
Repair or replace? How to think about it
There's no one answer, and anyone who gives you one before looking is guessing. Broadly:
When repair or recoat makes sense
The steel is still fundamentally sound, the issues are localised (a run of ridge capping, a valley, a patch of tiles), and you mainly need to stop a specific leak or buy a few more years. A targeted repair, or in some cases a recoat, can be a reasonable, cost-effective move.
When replacement is the better call
Rust is well established across the tile toes and fixings, the coating has broken down over large areas, or you're patching the same roof again and again. At that point repairs are money spent on a roof that's near the end of its life, and a fuller picture of the cost of replacement helps you plan rather than keep firefighting.
An assessment simply tells you, plainly, which of those situations you're in and sets out the options with the trade-offs clear, so the call is yours to make.
Decramastic roofs and insurance claims
These roofs visibly carry their age: rust, worn fixings, old patch repairs. So a storm leak on a decramastic roof is the kind an insurer may try to class as gradual deterioration or maintenance rather than sudden storm damage. The wind-driven leaks at ridges and valleys can also be hard to pin to a single, provable storm entry point.
We can document the visible condition and the likely cause in a plain-language assessment letter you can give your insurer, but we don't make the claim decision, and we don't provide a guaranteed leak diagnosis. If your claim has already been knocked back, our guide on why insurers decline roof leak claims and what to do next walks through your options.
How Aerial Assess can help
We're a Wellington-based, drone-assisted roof inspection and assessment service, and decramastic is one of the roof types we see most. We'll assess the visible and accessible areas of your roof, drone-assisted where access is difficult, document the condition and the likely source of any leak, and give you a clear, plain-language assessment letter with an honest repair-versus-replace read and your options laid out.
We cover Wellington, the Hutt Valley, Porirua, the Kāpiti Coast, and Wairarapa. No jargon, and no obligation to use us for any repair work that might come out of it. Your assessment fee stays the same either way.
Common questions
Is a decramastic roof the same as asbestos?
No. Decramastic roofs are pressed steel tiles with a stone-chip coating, there's no asbestos in the tile itself. People sometimes mix them up because both turn up on homes from a similar era. If you're worried about asbestos elsewhere on an older roof, such as old cement underlay or soffits, that's a separate question worth raising, but the decramastic tiles themselves are a metal product.
Can a decramastic roof be repaired, or does it need replacing?
It depends on the condition. If the steel is sound and the issues are localised (worn ridge or valley details, a few tiles, lost stone chips), a targeted repair or recoat can buy years. If rust is well established through the tiles and fixings, repairs become a patch on a roof that's near the end of its life, and replacement is the better call. The point of an assessment is to tell you which situation you're in, without pressure either way.
How do you inspect a decramastic roof?
We get close-up detail on the visible and accessible areas, with particular attention to the ridges, hips, valleys, dormers, and tile toes, the details where these roofs actually leak, plus the overall condition of the stone-chip coating and any rust. Where the roof is steep, high, or hard to reach, we use the drone to capture every visible surface. You get a clear, plain-language record of what we found, not a guess from the ground.
My decramastic roof leaks after storms but my claim was declined. Why?
Older decramastic roofs often carry visible age, rust on the tile toes, worn fixings, previous patch repairs, so insurers may class a leak as gradual deterioration or maintenance rather than sudden storm damage. We can document the visible condition and likely cause in plain language, but the claim decision is your insurer's. There's a separate guide on why roof leak claims get declined and what to do next.
How long does a decramastic roof last?
Many decramastic roofs in Wellington are now 40 to 50 years old or more, and a lot are at or near the end of their serviceable life. Lifespan depends on the exposure, how well the coating has held up, and whether rust has taken hold on cut edges and fixings. A coastal, weather-exposed roof ages faster. An assessment gives you a realistic read on how much life is left in yours.