Decramastic Roof Replacement Christchurch

Decramastic is a pressed steel tile coated in bitumen and stone chip, used on many New Zealand homes for decades because it looked like a tile without the weight. It was a popular lightweight roof, but as it ages the chip washes off, the steel underneath rusts and leaks follow. Once that is happening across the whole roof, replacement is usually the sensible answer.

Because some older decramastic contains asbestos in the bitumen layer, testing comes before anything else; our asbestos roof replacement page explains the rules. If you are still weighing repair against replacement, read our roof replacement guide first.

Pricing: every roof gets a free on-site measure and an itemised written quote, with a fixed price agreed before any work starts.

Decramastic Roof Replacement by Cheeky's Roofers roofers in Christchurch

Signs your decramastic roof is failing

Decramastic usually wears out slowly and then quickly. Chip loss starts on the most exposed faces and spreads, and once bare steel shows it has little protection left. Leaks then appear at overlaps, nail holes and valleys. Faces that take the full sun and the hot, dry nor'wester work hardest, so check those first.

Piles of stone chip in the spouting or at the foot of downpipes
Bare, black or rust-coloured patches where chip used to be
Tiles cracked, lifted or dented from being walked on
Rust spots on the underside, visible from the roof space
Moss and lichen holding damp against the tiles on shaded faces
Leaks at valleys, ridges and around flues

Why patching and painting rarely last

Single decramastic tiles can be replaced, and we do occasional repairs where one area has been damaged and the rest is sound. On an aged roof, though, patching chases a problem happening everywhere at once, and matching old tiles is hard.

Painting is often offered as the cheaper fix. The problem 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 laid before asbestos was phased out should be checked first. Painting an untested decramastic roof after water blasting it can contaminate your property.

How It Works

Roof inspection, photos and a tile sample sent for testing

Itemised quote based on the test result

Licensed removal and WorkSafe notification if asbestos is found

Battens off, purlins and underlay on, new steel installed

Flashings, ridging and spouting finished, then clean-up

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. A clear result means the tiles come off 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 polythene sheeting, low-pressure wetting and sealed waste bags. The removalists we use follow that guidance and take the waste to an approved disposal site.

Replacing decramastic with steel

With the tiles off, the job becomes a steel re-roof with one difference: decramastic sits on battens, and longrun steel needs purlins at a different spacing. We remove the battens, check the rafters, fix new purlins for the wind zone shown for your site, lay new underlay and install the new roof with fresh flashings and ridging. The full sequence is on our re-roofing page.

Decramastic is already a lightweight roof, so the change in weight is small, unlike a swap from concrete tiles. Most owners choose COLORSTEEL longrun in corrugate or a trapezoidal profile; the COLORSTEEL colours page shows the range. Cold, frosty Christchurch nights can bring condensation on the underside of a steel roof, so new underlay and a check of roof space ventilation are part of the job.

What affects the cost

The test result is the biggest variable. Clear means a straightforward strip and re-roof; positive adds licensed removal, notification and disposal. After that it comes down to roof area, pitch, the number of hips and valleys, access, timber replacement and the steel your environment needs. Homes in the beach suburbs such as New Brighton, Southshore and Sumner are checked against the manufacturer's environment categories for salt exposure. Your quote shows removal and roofing as separate lines.

Decramastic replacement across Christchurch

We replace decramastic roofs from the established streets of North Christchurch to the hill suburbs of the Port Hills and out to Selwyn and Waimakariri. Before any work starts we confirm which council is your building consent authority, because Christchurch City Council, Selwyn District Council and Waimakariri District Council each handle their own. On older homes in the city we also check the heritage rules under Plan Change 13. Find local detail on our North Christchurch and South and Port Hills pages.

Why Choose Cheeky's Roofers for Decramastic Roof Replacement

No water blasting

We never water blast an untested decramastic roof.

Tested before quoted

A lab result decides how the tiles come off, so the removal method is settled before you get a price.

Purlins done properly

Battens come off and purlins go on at the spacing and fixing the steel needs.

Clean spouting at the end

We flush out the loose chip so your new spouting and downpipes start clear.

Decramastic Roof Replacement FAQs

Does all decramastic contain asbestos?

No. Some older decramastic has asbestos in the bitumen layer and later tiles do not. Only a lab test tells you which you have.

Can I paint my decramastic roof?

It can be done on a roof that has tested clear and is still sound, but painting rarely fixes widespread chip loss and rust. Never water blast an untested roof.

Why is there grit in my spouting?

That is stone chip washing off the tiles. A little is normal on an older roof; a lot means the coating is failing.

Can you overlay a new roof on top of decramastic?

We do not recommend it. Overlaying hides the old roof's condition, leaves any asbestos in place and makes it hard to fix purlins properly.

Is steel heavier than decramastic?

Not by much. Both are lightweight roofs, so the change in weight is small.

How long does a decramastic replacement take?

About as long as any re-roof of the same size once testing is done, plus time for licensed removal if asbestos is found.

Decramastic Roof Replacement Across Christchurch

We cover every region: Central Christchurch, North Christchurch, East and Coastal Christchurch, South Christchurch and Port Hills, West Christchurch, Selwyn and Waimakariri.

Related Roofing Services

See the roof replacement cost guide or every service we offer.

Sources and further reading