The call usually starts the same way. “There are little black stones all through my gutters and I can’t work out where they’re coming from.” Look up and the answer is sitting right there: a decramastic roof that has been shedding its coating, one granule at a time, for years.
Decramastic tiles are pressed steel panels shaped to look like a row of tiles, coated in bitumen and finished with a layer of crushed stone chips. They went onto a lot of Australian homes in the 1970s and 80s, and plenty of brick veneers around Mornington, Mount Eliza and Rosebud still wear them. They were light, quick to lay and looked neat. Most of them are now tired, and the question we get asked is simple: fix it, coat it, or replace it?
The honest answer depends on three things. How much of the stone coating is left, whether the steel underneath has started to rust, and whether the coating contains asbestos. Here is how we work through each one.
Those stone chips are doing more work than they look
The chips aren’t decoration. They shield the bitumen from the sun, and the bitumen shields the steel. Once the chips wash off, UV starts cooking the bitumen. It goes brittle, cracks, and lets water sit directly on the steel.
From there it’s a slow slide. Rust starts on the surface, usually along the bottom edge of each tile where water lingers longest. Then it works through. Salt air off the bay speeds the whole process up, so homes closer to the water tend to get there first.
Signs your decramastic roof is near the end
You can spot most of these from the ground or from a ladder at the gutter line. Please don’t walk on the roof to check. More on why in a moment.
- Bare patches showing black bitumen or grey steel
- Rust spots on the lower lip of tiles and around nail heads
- Stone granules piling up in gutters or at the bottom of downpipes
- Tiles sitting crooked, or lifting and rattling in strong wind
- Brown water stains on the ceiling, often below a valley or near the ridge
- Dents and creases where someone has stood on the tiles
That last one surprises people. Decramastic tiles crush easily if you step in the wrong spot, and every dent cracks the coating and opens a new rust point. A lot of the damage we find traces back to a TV antenna install, a solar job or someone cleaning gutters from the roof. If you need a tradie up there, ask them how they plan to walk on it before they start.
Ceiling stains are worth taking seriously even if they only appear in big storms. Our post on why a roof only leaks in heavy rain covers how water travels before it shows up inside, which helps you work out where the problem actually starts.
Check for asbestos before anyone touches it
This is the step people skip, and it matters most. Some older bitumen coated imitation tiles, including some decramastic products, can contain asbestos in the coating or the adhesive. Not all of them do. You cannot tell by looking.
The only way to know is to have a sample tested by an accredited lab. Until you have that result, nobody should pressure wash, sand, cut or grind the roof, because those are the jobs that release fibres. If the test comes back positive, removing a whole roof of it is work for a licensed asbestos removalist under WorkSafe Victoria rules, and that shapes every option below.
A negative result is good news. It opens up all the choices and usually makes the job simpler.
A handful of bad tiles can be repaired
If the coating is mostly intact and the problems are local (a few dented tiles, some loose fixings, a leak around a flashing) then a targeted repair is often all you need. Flashings are the folded metal strips that seal joints, like where the roof meets a wall or chimney.
A typical repair means swapping damaged tiles for sound ones, refixing loose tiles with new screws, and resealing flashings and valleys. The catch is matching. Finding replacement tiles in the same profile and chip colour gets harder every year, so repaired sections can stand out a little. On the back of the house most people don’t mind. On the street side some do.
Coating a decramastic roof buys time, not a new roof
Restoring a decramastic roof means cleaning it gently, replacing the worst tiles, refixing everything, then applying a sealer made for bitumen surfaces and a flexible membrane coat on top. Done properly on the right roof, it can look good and keep the weather out for a good while yet.
The right roof is one where the steel is still sound. Coating over active rust just hides it, and the rust keeps going underneath until it lifts the new coat off. Cleaning is a balancing act too, because high pressure strips even more chips off a roof that can’t spare them. And again, none of it starts until the asbestos test comes back clear.
If restoration is on the table, it helps to know what goes into the number. We break that down in our guide to roof restoration pricing on the Peninsula, and most of it applies to decramastic roofs too.
When replacement is the honest answer
Widespread rust, leaks in more than one spot, lots of crushed tiles or a confirmed asbestos result usually point to replacement. Patching a roof in that state means paying for repairs again next winter.
Most decramastic roofs we replace go to Colorbond sheeting. There’s a practical reason for that. Decramastic is light, so the frame underneath was built to carry a light roof, and steel sheeting sits comfortably on it. Concrete or terracotta tiles are much heavier, and you’d want the frame checked before going that way. If you’re weighing the two, our Colorbond and tile comparison goes through the trade offs.
A full re-roof is also the best chance you’ll get to fix what’s underneath. Battens can be checked and replaced, sarking can go in, and old gutters can be swapped while everything is open. If you’re thinking about a metal roof replacement for an old decramastic home, we look at all of that during the inspection so there are no surprises halfway through.
What sets the price of a decramastic replacement
We don’t quote a decramastic roof off a photo, because the things that move the price are hard to see from the street. Size and pitch come first. A steep roof needs more safety gear and takes longer. Hips and valleys add cutting and flashing work. Access counts too, and a double storey home on a sloping Mount Martha block is a different job to a flat single storey in Somerville.
Then there’s what we find. Asbestos testing, and removal if it’s positive, is the biggest variable. Rotten battens, gutters that should be replaced at the same time, and extras like sarking or insulation all add to the total. A proper inspection is the only way to put real numbers on those.
Questions people ask about decramastic roofs
What is a decramastic roof?
It’s a roof made of pressed steel panels shaped to look like tiles, coated with bitumen and finished with crushed stone chips. They were common on Australian homes in the 1970s and 80s. From the street they can pass for a tiled roof, but they’re far lighter.
Are all decramastic roofs asbestos?
No, but some older bitumen coated imitation tiles do contain asbestos in the coating or adhesive. There’s no way to tell by eye. Get a sample lab tested before anyone cleans, cuts or removes the roof.
What is the typical lifespan of a decramastic roof?
There isn’t one figure that fits every roof. It comes down to how much stone coating is left, how much salt air it gets and how often it’s been walked on. Once rust shows up across many tiles rather than a few, the end usually comes quickly.
How much does it cost to replace a decramastic roof?
It depends on roof size, pitch, access, the condition of the battens and whether asbestos removal is needed. Asbestos is usually the biggest swing factor. An on site inspection is the only way to get a quote you can rely on.
How do I replace my decramastic roof tiles?
Individual tiles are unfixed, slid out from under the row above, replaced with a matching tile and fixed back down. It sounds simple, but walking on the roof to get there can dent the tiles around it. Have the coating tested for asbestos first, and leave it to a roofer who knows how to move across this type of roof.
If your gutters are full of black grit or the roof is showing rust, it’s worth having someone look before the next big storm. We can inspect your decramastic roof, tell you straight whether it needs a repair, a restoration or a replacement, and if it’s time, take you through our metal roof replacements service step by step.
