Decramastic is a pressed steel tile with a scalloped shape, a bitumen-based coating and a surface of stone chips. It was a popular roof on Auckland homes for many years because it looked like a tile without the weight. Many of those roofs are now old, and the way they fail is distinctive: the chip washes off, the coating breaks down, and the steel underneath starts to rust, often from the hidden side first.
There is a second issue. WorkSafe warns that decramastic roofing installed before asbestos was phased out may contain asbestos in its coating, and in one case tiles on a 1970s home tested positive for chrysotile. That changes how the roof must be handled, cleaned and removed. This page covers both the roofing and the safety side. For other older roofing materials, see asbestos roof replacement.
Pricing: every roof gets a free on-site measure and an itemised written quote, with a fixed price agreed before any work starts.
Signs your decramastic roof is failing
Decramastic roofs tend to fail gradually and then all at once. Chip loss starts on the most exposed faces and spreads, and once the steel is exposed it has little protection left and starts to corrode. Leaks then appear at tile overlaps, nail holes and valleys.
- Heaps of stone chip in the spouting or at the bottom of downpipes
- Bare, black or rust-coloured patches where chip used to be
- Tiles that are cracked, lifted or dented from being walked on
- Rust spots on the underside, visible from the roof space
- Heavy moss and lichen holding moisture against the tiles
- Leaks at valleys, ridges and around flues
Why repairs and painting rarely last
Individual decramastic tiles can be replaced, and we do occasional tile repairs where one area has been damaged and the rest of the roof is sound. On an aged roof, though, patching chases a problem that is happening everywhere at once, and matching old tiles is difficult.
Painting is often offered as a cheaper fix. The catch is preparation. WorkSafe has issued a safety alert that high-pressure water spraying, including water blasting, must not be used on asbestos or asbestos-containing material, and that decramastic roofs installed before asbestos was phased out should be checked first. Painting an untested decramastic roof after water blasting can contaminate your property. If you want to compare options, read our roof replacement guide on deciding between repair and replacement.
How It Works
Asbestos testing comes first
Before we quote to remove a decramastic roof, we arrange for a tile sample to be tested by an accredited laboratory. If the result is clear, the tiles are removed as part of a normal re-roof. If asbestos is present, removal follows WorkSafe rules: more than 10 square metres of asbestos-containing material must be removed by a licensed removalist, who must notify WorkSafe in writing at least five days before starting.
WorkSafe publishes specific guidance for removing metal cladding lined with asbestos-containing bitumen, including the use of polythene sheeting, low-pressure wetting and sealed waste bags. Removalists we work with follow that guidance, and the waste goes to an approved disposal site.
Replacing decramastic with COLORSTEEL
Once the tiles are off, the job becomes a standard steel re-roof with one difference: decramastic is fixed to battens, and a longrun roof needs purlins at a different spacing. We remove the battens, check the rafters, fix new purlins for your wind zone, lay new underlay and install the new roof with fresh flashings and ridging. The full sequence is on our re-roofing page.
Most owners choose longrun COLORSTEEL in corrugate or a trapezoidal profile. Because decramastic is already a lightweight roof, the change in load is small, unlike a conversion from concrete tiles. The COLORSTEEL colours page shows the range.
What affects the cost
The biggest variable is the asbestos test result. A clear result means a straightforward strip and re-roof. A positive result adds licensed removal, notification and disposal. After that, price depends on roof area, pitch, number of hips and valleys, access, timber replacement and the steel grade your site needs. Coastal homes, particularly in the eastern bays, on the North Shore and around the Hibiscus Coast, may sit in a harsher environment category than inland suburbs. Your quote shows removal and roofing as separate lines.
Why Choose Cheeky's Roofers for Decramastic Roof Replacement
No water blasting
We never water blast or pressure clean a decramastic roof before it has been tested.
Tested before quoted
We get a lab result first so your quote reflects how the tiles must legally be removed.
Battens replaced properly
Old tile battens come off and purlins go on at the spacing the new steel needs.
Chip-free spouting
We clear the spouting and downpipes of years of shed chip as part of the job.
Decramastic Roof Replacement FAQs
Does all decramastic contain asbestos?
No, but some older decramastic has tested positive, and you cannot tell by looking. A lab test is the only way to know.
Can I paint my decramastic roof?
Painting can extend life on a sound roof, but preparation must not involve water blasting unless the tiles have tested clear of asbestos. On a roof that is losing chip and rusting, painting rarely lasts.
Why is there grit in my spouting?
That is stone chip coming off the tiles. Once the chip goes, the coating and steel underneath are exposed and wear faster.
Can you overlay a new roof on top of decramastic?
Some manufacturers offer overlay systems for decramastic roofs. We assess each roof individually and generally recommend removal so the timber and underlay can be checked and replaced.
Is a new steel roof heavier than decramastic?
Both are lightweight roofs, so the load on the frame changes very little.
How long does a decramastic replacement take?
Similar to a standard re-roof once removal is done. If asbestos is present, allow extra time for testing and the five-day notification before licensed removal.
Decramastic Roof Replacement by Area
Local decramastic roof replacement information for your part of Auckland:
Related Roofing Services
- Re-Roofing
- Roof Replacement
- Tile to Metal Re-Roofing
- Asbestos Roof Replacement
- Roof Repairs
- Roof Painting
Decramastic Roof Replacement Guides
See the re-roofing cost guide or every service we offer.
Sources and further reading
- WorkSafe: Check for asbestos before high-pressure spraying on roofs (safety alert)
- WorkSafe: Removing metal cladding lined with asbestos-containing bitumen
- WorkSafe: Asbestos licensing overview
- WorkSafe: Duty to notify licensed asbestos removal
- COLORSTEEL: products by environment category
- NZ Metal Roof and Wall Cladding Code of Practice