Quick answer: Decramastic roof painting can give a sound original roof more years, but only after an asbestos test, without high-pressure water blasting, and with a waterborne primer system that won’t soften the bitumen under the stone chip.
You clean the gutters and they’re full of grit: little dark stone chips, far more than a season’s worth. Up on the roof, the scalloped tiles have gone patchy, with smooth black areas where the chip used to be and a rust stain or two along the laps. If your house went up between the late 1950s and the early 1980s, there’s a good chance you’re looking at an original Decramastic roof, and the question is whether paint will save it.
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Often it can. Resene publishes a specific repaint system for these roofs, and the roof industry’s own body says many of them have been, or can be, restored.
But a Decramastic repaint is not an ordinary roof job. The old coating can contain asbestos, which changes how the roof can be cleaned. The bitumen under the chip reacts badly to the wrong primer. And a roof that has rusted through is past the point where paint helps.
Get those three things right and a repaint is a sensible, much cheaper alternative to a new roof. Get them wrong and you pay for a paint job that fails early, or a cleanup you didn’t plan for.
What a Decramastic Roof Is, and Why It Matters Before Anyone Paints It
“Decramastic” gets used for almost any pressed-metal tile roof with a gritty finish, but the name belongs to a specific, older product. Knowing which kind of roof you have is the first decision in the whole job, because the original product and its modern successors are built differently and are prepared differently.
The original product: steel, bitumen and stone chip
According to Gerard Roofs, whose parent company made the product, Decramastic tiles were galvanised steel with stone chip embedded in a bituminous coating, and they were popular in New Zealand in the 1960s and 1970s. Resene’s roof-painting guide describes the same build from the painter’s side: pressed galvanised iron, a bitumen basecoat over it, and stone chips set into that basecoat.
The New Zealand Metal Roofing Manufacturers association dates the first tiles to 1957. It says AHI Roofing began research into acrylic coatings in 1976, and by 1980 the new acrylic-based product had replaced the old bituminous emulsion. So the bitumen-coated roof is a product of roughly two decades, and a lot of those roofs are still on Auckland houses.
Where do you find them? Our own cost guide notes that Decramastic and concrete tile turn up constantly on the 1960s to 1980s housing of South and East Auckland, in suburbs like Manukau, Papatoetoe, Papakura, Howick, Pakuranga and Botany, and on older homes across the North Shore. A scalloped, chip-coated roof on a brick-and-tile or weatherboard house from that era is the classic case.
Today’s stone-coated tiles are a different roof
The same association is blunt that modern pressed-metal tiles are not Decramastic. It says today’s tiles use a ZINCALUME® steel base, an acrylic coat laid over with natural stone chip, and a second acrylic overglaze, and that none of the current makers use bituminous products. Gerard makes the same point: the old tiles have been superseded by today’s pressed steel tiles.
That difference matters for paint. The system in this guide is built around the problems of the bitumen-coated original: chip loss that exposes soft black bitumen, and bitumen that can be softened by solvent. A newer acrylic stone-coated roof doesn’t have the bitumen layer, so its maker’s care instructions are the place to start, not an old-roof repaint system.
How to tell which roof you have
Start with the date. If the roof is original to a house built before the early 1980s, treat it as the bitumen-coated product until you know otherwise. Then look closely at a damaged area, from a ladder at the gutter rather than by walking the roof. On an old Decramastic roof, where chip has come away you’ll usually see a black, tar-like layer underneath, and further gone, bare grey galvanising or rust. Grit in the gutters and downpipes is the other giveaway.
None of that tells you what’s in the coating, though. The look of a roof can narrow down its age. It can’t tell you whether the bitumen contains asbestos, and that is the question that decides how the roof can be cleaned. That needs a lab test, which is the subject of the next section.
🎨 Painting tip: Check the property file before anyone gets on the roof. A building consent record, an earlier builder’s report or the original sale paperwork can date the roof, and a roof that was replaced in the 1990s is a different job from one that has been there since the house was built.
What an ageing Decramastic roof looks like
Resene’s guide sets out the order in which these roofs wear: over time the stone chips erode, exposing the bitumen, then eventually the galvanised iron, which will ultimately rust. You can read where a roof sits on that path from the ground and the gutters.
- Early: a scattering of chip in the gutters, the colour fading unevenly, moss and lichen in the shaded valleys and on the south face.
- Middle: smooth black patches where the chip has gone, most often on the leading edges of the tiles and the most exposed faces.
- Late: bare grey steel showing through the bitumen, then rust spots, often starting at the laps where tiles overlap.
- Past paint: rust that has eaten through the steel, tiles that let daylight in, or water stains on the ceiling below.
The first three stages are what a repaint is for. The fourth is a roofing problem, and we come back to it below. Dents are a separate issue. A roof that has been walked on badly over the years can carry dented or cracked tiles that need a roofer’s attention before any coating goes on. A coat of paint will not close a split.
Decramastic Asbestos: Why the Test Comes Before the Wash
This is the part that makes a Decramastic repaint different from every other roof we paint. The original bituminous coating can contain asbestos, and in New Zealand that rules out the cleaning method most people picture when they think of roof prep.
What the makers and regulators say
Gerard’s page on re-roofing over decramastic tiles says asbestos was used until 1981, with some roofs possibly installed as late as 1982, and that a roof installed before then has a high chance of containing a small amount of asbestos. It also says anyone re-roofing such a house will first want an asbestos test.
The Australian Government’s Asbestos Product Guide lists the same product by name. It records that Decramastic was first produced in 1957 by AHI Roofing (NZ), that the bituminous mastic coating on the top of the steel contained asbestos, and that use of that coating ceased in the early 1980s. Its advice is to assume asbestos is present until testing shows otherwise. It also warns that the coating’s adhesion can deteriorate through weathering and that asbestos-containing debris is likely in the gutters.
That last point is easy to miss. The chip and coating that have already come off the roof are sitting in your gutters and downpipes. Clearing them by hand, flushing them out with a hose at full blast, or scooping them into the garden is handling the same material the test is asking about.
Why a water blaster is off the table
Most roof repaints start with a thorough clean, and on a lot of roofs that means water blasting. On a Decramastic roof that may contain asbestos, it can’t. The Health and Safety at Work (Asbestos) Regulations 2016 say, in regulation 18, that a business must not use, or direct or allow a worker to use, a high-pressure water spray or compressed air on asbestos or asbestos-containing material. The regulations define high-pressure water spray as water from pumps with an output capability of more than 350 kPa.
The same regulation goes further. A business must not use a power tool, a broom, or any other implement that releases airborne asbestos on asbestos-containing material unless that use is controlled, which the regulation defines as the equipment being enclosed or designed to capture or suppress the dust. That covers the power wire brushing a painter would normally use on rust spots.
There’s a practical reason to avoid high pressure on this roof even without the asbestos question. As our comparison of soft washing and water blasting explains, a strong jet strips stone chip from an aged Decramastic roof that was still doing its job. You’d be removing the very surface you’re trying to keep.
Important note: Asbestos testing, removal and disposal, re-roofing, and any repair to the roof structure are specialist and regulated work. Get an asbestos test from a specialist testing company, and talk to a Licensed Building Practitioner roofer or Auckland Council about anything beyond cleaning and coating the existing roof. This guide does not replace their advice.
What the test result changes
A test result doesn’t decide whether the roof can be painted. It decides how the job is run. If the coating is clear, prep follows the normal low-pressure method for a chip-coated roof. If it contains asbestos, the painting contractor’s prep has to fit within the regulations: no high-pressure water, no compressed air, and controlled methods for anything that abrades the surface. Ask the contractor how the gutter debris will be cleared and disposed of, rather than leaving it to be tipped in the bin.
A positive result also changes the replacement maths, and Gerard says so directly. If the roof ever has to come off, a specialist asbestos removal company removes it before a roofer replaces it, which adds cost to a new roof. That’s part of why so many owners of these roofs look hard at coating first.
🎨 Painting tip: Ask any painter quoting your Decramastic roof one plain question: how will you clean it? If the answer is “water blast it”, and nobody has mentioned a test, keep looking.
Lead in an earlier repaint
Some Decramastic roofs were painted once already, decades ago. Resene’s Summit Roof data sheet says lead testing of existing roof coatings, including primers, should be done on roofs installed before 1971, or older roofs that haven’t been stripped of coatings applied before that date. So an early Decramastic roof with an old coat of paint on it can need two tests, one for the bitumen and one for the paint.
How a Decramastic Roof Is Painted: Resene’s Repaint System, Step by Step
Resene’s roof-painting guide has a section on Decramastic roofs, and it’s the most specific published system we know of for them. Its summary is honest: painting is relatively straightforward, but the topcoats need to be sprayed if you want a reasonable finish. Below, each step sits alongside what that product’s own data sheet says.
Cleaning and priming without harming the bitumen
Step one: kill the growth, then wash gently
Resene’s system starts with treating moss and mould and washing the roof down thoroughly. Its guide names Resene Deep Clean as ideal for decramastic and tile roofs where the aim is to kill moss and mould. The Deep Clean data sheet explains why this step takes time: it’s slow acting, it’s applied by brush or low-pressure spray and left on rather than rinsed, and it can take up to a week to see any visible effect on lichen, mould and algae. Heavy growth may need a second application.
That slow kill suits this roof. A chemical that does the work over days lets the dead growth be washed off with low pressure, instead of being blasted off along with the chip. The data sheet adds two cautions that matter on a house: keep the product away from plants, stormwater outlets and streams, and don’t store or apply it with mild steel or aluminium equipment, which it attacks.
Step two: prime the bare steel with a waterborne primer
Where chip and bitumen have worn through to bare galvanising, those spots need a primer. Resene’s guide recommends spot priming them with Resene Galvo-Prime, and gives the reason. Its solventborne primer, Galvo One, performs better on aged galvanised iron but will also soften the residual bitumen coating, which the waterborne Galvo-Prime won’t. On a Decramastic roof, the choice of primer is about protecting the bitumen as much as the steel.
The Galvo-Prime data sheet adds the limits. It isn’t recommended where white rust is present (Galvo One is the alternative) or where red rust is present (spot prime with Resene Rust-Arrest first), and it isn’t recommended under solventborne roof paints. On a repaint it says to spot prime bare and lightly rusted areas with one coat. That’s where the asbestos result comes back in: removing red rust normally means wire brushing, and on a roof with asbestos in the coating that has to be done by a controlled method.
Step three: seal any large areas of bare bitumen
Where wide patches of chip have gone and the black bitumen is exposed, Resene’s guide calls for spot priming those areas with its membrane roofing primer. The current Membrane Primer data sheet lists bituminous substrates among its typical uses, says one coat is sufficient, and says it must be overcoated within three months because it isn’t designed to protect long term on its own. It names Resene Lumbersider among the topcoats for it.
One line on that data sheet explains the whole logic of the system. The primer will not isolate bituminous substrates from solventborne topcoats. In plain terms, this roof needs a waterborne system from primer to finish, because a solvent-based paint would still reach and soften the bitumen even over the primer.
Rebuilding the texture and spraying the finish
Step four: build back the worn chip areas
This is the step most repaint quotes skip. Resene’s guide says to brush Resene Resitex Coarse onto the areas where stone chip has eroded, and is candid that while not perfect, it helps make good the tiles. The idea is to restore some texture where the roof has gone smooth, so the finished coat doesn’t show a patchwork of flat and gritty areas.
The Resitex data sheet describes it as an elastomeric textured coating that remains flexible, warns against applying it below 10°C or when the temperature may drop below 10°C during drying, and notes that coarse textures may hold more airborne dirt. That temperature limit is one reason we plan these roofs for the warmer months.
Step five: two sprayed coats, leading edges first
The finish in Resene’s system is two coats of Resene Lumbersider. The guide says its lower gloss, compared with Resene’s high-gloss roof paint, helps disguise patchiness, which is exactly what a weathered chip roof needs. The Lumbersider data sheet describes it as excellent as a roof coating where a low sheen finish is required, and says it shouldn’t be applied below 10°C or when the temperature is likely to drop below 10°C while it dries.
Technique matters as much as product. The guide says to apply paint to the leading edge of each tile first when spraying the topcoats, and notes that extension poles for spray units make this easier. Those front edges are the most exposed part of every tile, the first place chip wears, and the hardest to reach once the faces are wet.
🎨 Painting tip: Ask for the system in writing, product by product. A Decramastic quote should name the cleaner, the primer for bare steel, the primer for bare bitumen, any chip-repair coat and the topcoat, and say whether the topcoats are sprayed. If it just says “roof paint, two coats”, ask what goes underneath.
Why it takes longer than a smooth roof
Add those steps up and the time difference makes sense. A smooth steel roof is washed, spot primed and painted. A Decramastic roof needs a slow chemical clean with time to work, two kinds of spot priming, a textured repair coat in the worn areas, and two sprayed topcoats applied tile edge by tile edge. Each coat also has a minimum temperature, and the primers have recoat windows. That’s why our price ranges put Decramastic with concrete tile rather than with iron.
Paint, Overlay or Replace: Making the Call on an Auckland Decramastic Roof
A repaint is one of three options for an ageing Decramastic roof. The other two are a new roof laid over the old one, and a full replacement, and the line between them is the condition of the steel.
When a repaint is the right call
Painting suits a roof that is still sound under its worn surface: the steel is intact, the tiles are fixed and mostly undamaged, and the chip loss and rust are patchy rather than general. That’s the roof Resene’s system is written for. It treats the growth, protects the exposed steel and bitumen, rebuilds texture where the chip has gone, and puts a fresh low-sheen colour over all of it.
For a lot of owners, the appeal is what a repaint avoids. The roof stays on, the asbestos question stays contained within the cleaning method, and the house gets a new colour on its biggest surface. The metal roofing manufacturers’ association notes that many of these roofs are still in service around 50 years on, and that they have been or can be restored with modern technology.
When paint is only a delay
Our guide to weighing a roof repaint against a new roof puts it plainly: on decramastic stone-chip tiles, bare rusting steel showing through the lost chip coating signals end of life. Paint can’t put metal back. If rust has gone through the steel, if tiles are split or holed, or if water is already getting in, the roof needs a roofer before it needs a painter, and often it needs replacing.
We’ll tell you that upfront. A paint job sold onto a roof that is failing underneath is money spent on a delay, and it leaves you with the same decision a few years later, plus the cost of the paint.
Overlay and full replacement
Gerard markets an overlay option: it says its concealed-fastening CF Shake tile can be laid directly over an existing decramastic roof, keeping the old tiles and any asbestos in them in place rather than removing them. Full replacement means stripping the old roof, with asbestos removal first if the test is positive, then laying a new one.
Both are roofing jobs, not painting jobs, and both carry costs that a painting contractor shouldn’t be guessing at. For the numbers on that route, Superior Renovations has a guide to what reroofing an Auckland home costs. Talk to a Licensed Building Practitioner roofer about any structural or weathertightness work, and to Auckland Council if you’re unsure whether the work you’re planning needs consent.
🎨 Painting tip: If you’re torn between paint and a new roof, get the roofer’s condition report first. A painter can price a coating, but a roofer can tell you how many tiles, flashings or battens need attention before any coating is worth putting on.
If you collect rainwater from the roof
If your household drinks water collected off the roof, the products matter twice over. Both the topcoat and the bare-steel primer in this system are rated for it. The Lumbersider data sheet says it may be used on surfaces used for collecting drinking water, and the Galvo-Prime data sheet says it is suitable for drinking-water collection. Both carry the same instruction: disconnect the roof downpipes until after the first shower of rain, to flush away surplus non-toxic wetting agents before the water is collected.
The cleaning stage needs the same care. Deep Clean is left on the roof to work, so plan with your painter to keep the tank disconnected through the clean and the coating, and think about how the gutter debris will be cleared before the downpipes go back on, particularly if the asbestos test was positive.
Decramastic Roof Painting Cost, Access and How We Run the Job
Our prices come from our own Auckland roof jobs, and our roof painting price guide for each size of home is where we keep them. Decramastic sits in the same band as concrete tile, because both need more prep and primer than a smooth iron roof.
Our price ranges for tile and Decramastic roofs
| Home / roof size | Tile / Decramastic (indicative, excluding GST) | Iron roof, for comparison (excluding GST) |
|---|---|---|
| Small (under 100m²) | $4,500–$7,000 | $2,500–$4,000 |
| Standard (100–200m²) | $7,000–$12,000 | $3,500–$6,500 |
| Large (200–300m²) | $11,000–$16,000+ | $6,500–$9,500 |
| Two-storey access uplift | Add 20–40% for scaffolding and edge protection on most two-storey jobs | |
These are indicative ranges for a fully prepped and coated roof, and they exclude GST. Where a particular roof lands depends on how much chip has gone, how much rust needs treating, how many tiles need a roofer first, and access. They don’t include asbestos testing, asbestos removal or roofing repairs, which are separate trades. For a figure built around your own roof size and type, the calculator above emails you an Auckland range.
How far the wear has gone moves the price more than the size of the roof. A roof with a few smooth patches needs little textured repair and spot priming, while one with chip loss across every face needs a lot of both.
Rust is the other big variable. Light rust is spot primed. Red rust has to be removed first, and on a roof with asbestos in the coating that means slower, controlled methods. Access, covered below, adds the rest.
Weather affects the schedule more than the price. With minimum application temperatures of 10°C on both Resitex and Lumbersider, and a slow chemical clean that needs dry days to work, these roofs suit Auckland’s drier, warmer months, roughly late spring to early autumn. A winter booking usually means waiting for the right run of days.
🎨 Painting tip: Compare quotes on the system, not just the total. Two prices for the same Decramastic roof can differ because one includes the chip-repair coat and controlled rust removal and the other doesn’t, and only one of those roofs will look even when it’s finished.
Access and safety on a metal tile roof
WorkSafe’s good practice guidelines for working at height say there is no minimum height threshold in New Zealand: any fall risk from any height must be managed. WorkSafe recommends that any potential fall greater than one metre be managed with physical barriers or fall restraint. On roofs, edge protection should be both system-rated and fitted with infill panels where the pitch is over 25°, and designed specifically for slopes over 35°.
The guidelines also set two 5 m thresholds. Scaffolds from which a worker or object could fall more than 5 m should be put up by, or under the direct supervision of, a person with an appropriate certificate of competence, and work with a risk of falling 5 m or more must be notified to WorkSafe at least 24 hours before it starts. An honest Decramastic quote names the access method it has priced, because on a two-storey house that’s where the 20–40% uplift goes.
There’s a second reason access matters on this roof. Pressed-metal tiles dent if they’re walked on in the wrong place, and every dent is a spot where the coating can crack and the chip can let go. Good roof painters plan their walking lines and use crawl boards where needed, so the job doesn’t create damage it then has to paint over.
Questions to ask before you book anyone
Most of what goes wrong on these roofs is decided before the first coat, in what the quote leaves out. These questions sort the quotes quickly:
- Has the roof been identified as original bituminous Decramastic or a later acrylic tile, and how?
- Will you test for asbestos, or work from a test I already have, before the clean is planned?
- How will you clean the roof and the gutters, and at what pressure?
- Which primer goes on bare steel, and which on bare bitumen? Is the whole system waterborne?
- How are the worn chip areas made good before the topcoats, and are the topcoats sprayed?
- What access have you priced, and who handles the downpipes if we collect rainwater?
A painter who has done these roofs will answer every one of these without hesitating. Vague answers to the cleaning and primer questions are the ones to worry about, because those are the two steps that can damage the roof rather than protect it.
How we run a Decramastic repaint
Every roof repaint Superior Painters takes on has a dedicated project manager who is on site each day and is your sole point of contact, from the first site visit to the final inspection. On a Decramastic roof that means we confirm the roof type and the asbestos test result before the clean is planned, agree the system product by product, schedule around the temperature limits, and check the finished roof against our 97-point quality checklist. The work sits under our Picture Perfect guarantee, our promise of a “magazine worthy” result.
Not every roof we look at gets a painting quote, and we’d rather say so than sell you a coat that won’t last. If the steel has gone, we’ll tell you it’s a roofer’s job.
Your Decramastic Roof, Repainted Before the Steel Goes
An original Decramastic roof gives you a window. While the steel is sound, a test, a gentle clean and a waterborne system can put a new finish over decades of wear for a fraction of what a new roof costs. Once the rust is through, the window has closed. The best time to price a repaint is when the gutters first start filling with chip, not when the ceiling starts to stain.
➡ Book a free consultation with Superior Painters
➡ See our before and after painting transformations
➡ Talk to us about recoating a stone-chip metal tile roof
Can a Decramastic roof be painted?
Yes, if the steel is still sound. Resene publishes a repaint system for Decramastic roofs: treat moss and mould and wash, spot prime bare steel with waterborne Galvo-Prime, prime large areas of bare bitumen, brush Resitex Coarse onto worn chip areas, then spray two coats of Lumbersider. Once rust has gone through the steel, paint is only a delay.
Does my Decramastic roof contain asbestos?
It may. Gerard Roofs says asbestos was used until 1981 and that roofs installed before then have a high chance of containing a small amount. The Australian Government's Asbestos Product Guide says to assume the bituminous coating contains asbestos until a lab test shows otherwise. The only way to know is to have a sample tested.
Can you water blast a Decramastic roof?
Not if it may contain asbestos. Regulation 18 of the Health and Safety at Work (Asbestos) Regulations 2016 bars a business from using high-pressure water spray, meaning over 350 kPa, or compressed air on asbestos-containing material. High pressure also strips stone chip that was still protecting the roof, so a slow chemical clean and low-pressure wash is the method.
How much does it cost to paint a Decramastic roof in Auckland?
On our own Auckland jobs, tile and Decramastic roofs run $4,500–$7,000 under 100m², $7,000–$12,000 for 100–200m² and $11,000–$16,000+ for 200–300m², excluding GST. Add 20–40% for scaffolding and edge protection on most two-storey homes. Asbestos testing, removal and roof repairs are extra.
What primer should be used on a Decramastic roof?
Resene recommends its waterborne Galvo-Prime on bare galvanised steel, because its solventborne Galvo One softens the residual bitumen coating. Large areas of bare bitumen get Resene Membrane Primer, which lists bituminous substrates among its uses. Its data sheet says it won't isolate bitumen from solventborne topcoats, so the whole system stays waterborne.
How do I know if my roof is Decramastic or a modern stone-coated tile?
Age is the first clue. The New Zealand Metal Roofing Manufacturers association says acrylic replaced the old bituminous coating by 1980, and today's tiles use a Zincalume base with acrylic coats and no bitumen. An original roof on a house built before the early 1980s, with black bitumen showing where chip has worn, is likely the old product.
Why is there stone chip in my gutters?
Resene's roof guide says the stone chips on Decramastic tiles erode over time, exposing the bitumen and then the galvanised steel, which eventually rusts. Grit in the gutters is that erosion in progress. On an older roof treat the debris with care, because the Asbestos Product Guide warns that asbestos-containing debris is likely in the guttering.
Should I paint or replace my Decramastic roof?
Paint suits a roof that is sound underneath, with patchy chip loss and light rust. Replace or call a roofer when rust has gone through the steel, tiles are split or holed, or water is getting in. Gerard also markets an overlay tile that goes over the old roof. Overlay and replacement are roofing jobs for a Licensed Building Practitioner roofer.
Can I collect drinking water from a painted Decramastic roof?
With the Resene system, yes. The Lumbersider and Galvo-Prime data sheets both say the products can be used on surfaces that collect drinking water. Both say to disconnect the roof downpipes until after the first shower of rain to flush away surplus wetting agents, and keep the tank disconnected through the cleaning stage too.
When is the best time to paint a Decramastic roof in Auckland?
The drier, warmer months, roughly late spring to early autumn. Resene's Resitex and Lumbersider data sheets both say not to apply below 10°C or when the temperature may drop below 10°C while drying, and the slow moss and mould clean needs a run of dry days to work before the roof is washed and coated.
Related guides
- Repainting a COLORSTEEL roof before the steel suffers
- When paint works on a concrete tile roof and when it doesn’t
- Reading the signs that a house or roof is due for paint
References
- Resene, Painting roofs (Popular Paint Systems guide)
- Resene, Galvo-Prime waterborne galvanised steel primer data sheet D402
- Resene, Membrane Primer data sheet D49
- Resene, Resitex elastomeric textured coating data sheet D70
- Resene, Lumbersider Low Sheen data sheet D34
- Resene, Deep Clean data sheet D815
- Resene, Summit Roof data sheet D315S
- Gerard Roofs, What are decramastic roof tiles?
- Gerard Roofs, Re-roofing over decramastic tiles
- New Zealand Metal Roofing Manufacturers, Today’s metal tiles are not “Decramastic”
- Asbestos Safety and Eradication Agency (Australian Government), Asbestos Product Guide: bituminous coated imitation roof tiles
- New Zealand Legislation, Health and Safety at Work (Asbestos) Regulations 2016
- WorkSafe New Zealand, Working at height in New Zealand: good practice guidelines