How To Remove Mould From Fabric

Nobody reroofs a house for fun. It happens because something has started leaking, or because a storm took a few sheets, or because the tiles have been slipping for three years and you have run out of ways to not think about it.

Then the quotes arrive and they do not agree, and the sales pitch for going from tiles to Colorbond sounds a lot like a free upgrade.

It is not, and the reason why is the most useful thing in this guide. A government investigation has already measured what happens when that conversion is done badly, and it is not a cosmetic problem.

So this covers what the numbers can actually be traced to, what BlueScope itself says about its own product, and what changes structurally when the weight comes off your roof.

What The Independent Cost Data Shows

The only free, independent Australian source publishing roofing rates is the Archicentre Australia Cost Guide 2026.

Archicentre Australia Cost Guide 2026, including GST, for roofing up to two storeys fixed to an existing roof frame.

That qualifier is the important part, and the guide is refreshingly direct about it. The rates are for covering fixed to an existing frame, and the roofing section ends with the instruction "allow extra for: framing upgrade." The cost guide publisher is telling you the structural work sits outside the rate.

There is also no roof removal, demolition or asbestos line item anywhere in the guide, so strip-out is excluded too.

The Figures You Cannot Source

We went looking for support for the numbers that circulate on this topic and could not find it.

There is no credible published source for a total of $18,000 to $24,000 for a Colorbond reroof. Not from Archicentre, Rawlinsons, BMT, the Housing Industry Association, Master Builders, CHOICE, the ABS or any regulator.

There is no credible source for roof removal and disposal at $1,000 to $3,000 either. Worth noting, with a raised eyebrow, that the Archicentre guide's tree removal line is $1,500 to $3,000 per tree. If that is where the figure originally came from, it has travelled a long way from home.

So treat any single total you see, including on this page, as somebody's market observation. What you can do is take your roof area, multiply by the Archicentre band, then add strip-out, disposal, access and framing as separate lines. That will not give you a price, but it will tell you whether a quote is structured honestly.

What Actually Changes When You Swap Tiles For Steel

This is the section worth reading twice, because the usual explanation has the engineering backwards.

You will be told that lighter sheets need "minor structural adjustments" because the frame no longer carries as much weight. The opposite is closer to the truth.

James Cook University's Cyclone Testing Station states it plainly: the mass of a sheet roof is significantly less than the mass of a tile roof, which means the design wind uplift produces a higher net uplift at the top of the wall. Tile roofs use their own weight to help stay put. Remove the weight and the wind loads that were previously offset by mass now have to be carried entirely by the tie-downs.

Which means the tie-down chain, running from the sheeting through the battens, rafters and walls down to the footings, has to be reassessed under AS 1684 and usually upgraded.

What The Regulator Found

In July 2021, Western Australia's Building and Energy division published an investigation conducted with the Cyclone Testing Station, analysing 15 years of wind damage across cyclonic and non-cyclonic regions.

Of Perth metropolitan roofs lost in storms, about half involved lightweight metal sheet cladding that had replaced the original heavy tile or asbestos cladding. Those modified roofs were damaged even when winds did not exceed the speeds building standards require them to withstand. The recurring causes were inadequate tie-downs and re-roofing work carried out without the required building permits or licences.

A 2024 follow-up report on two severe wind events in Bunbury found the same pattern in more detail. Around 90 per cent of houses in the area had tile roofs, yet most severely damaged roofs were sheet metal. Investigators found roofs where the original tile battens were still visible under the failed sheet roof, with no strengthened tie-downs installed at all. In one event, winds reached only about 75 per cent of design wind speed, roughly half the design loads, and previously replaced sheet roofs still failed.

That is the point that matters. These are not freak-weather failures. They are failures well below what the building standards assume the roof can survive.

What That Means For Your Quote

Western Australia's Building and Energy factsheet for homeowners is direct: changing to a lighter roof covering may involve upgraded tie-downs to prevent the roof from blowing away, a building permit will likely be required when replacing a roof covering with a material of a different weight or shape, and it is an offence to start such work before the permit is granted. It tells homeowners to use competent people, such as a structural engineer or a registered builder with relevant qualifications, to check the existing roof structure.

Battens matter too. The National Construction Code specifies sheet roofing fixings and batten requirements separately from tile roofing, so existing tile battens cannot be assumed suitable for steel sheeting.

Ask three questions of anyone quoting a tile-to-Colorbond conversion: what happens to the tie-downs, whether an engineer has assessed the structure, and whether a building permit has been applied for. If the answer to all three is vague, that is the single most useful thing the quote has told you.

Western Australia appears to be the only Australian regulator that has published a finding on this. That does not mean it is a Western Australian problem.

What BlueScope Actually Says About Colorbond

Some of the most repeated Colorbond claims do not come from BlueScope at all.

The 50 Year Figure

The claim that a Colorbond roof lasts up to 50 years is not traceable to BlueScope. It does not appear on the Colorbond site, in the product datasheet, or in the technical bulletin covering product selection, which says only that selecting the correct product for the location will contribute to a long service life.

The number that does appear is 60 years, and it refers to the duration of BlueScope's outdoor exposure and laboratory testing programme and how long the product has existed. It is not a lifespan.

There Is No Standard Warranty Period

BlueScope's published sample warranties are templates containing literal placeholders, reading "{WARRANTY PERIOD} years from {INSTALLATION DATE}". Its own position is that it offers a variety of warranties subject to application and eligibility criteria, and that availability and duration depend on factors including location and how the products are installed. Warranties are issued project by project through a warranty management system that determines eligibility and duration.

So a roofer quoting you a fixed warranty figure is quoting something BlueScope does not publish. Ask them to apply for the actual warranty for your address and product.

Maintenance Is A Warranty Condition, And It Is More Than An Occasional Hose

The commonly repeated version is that Colorbond needs only a regular wash with fresh water. The actual requirement is more specific and it is a condition of cover.

BlueScope's sample warranty conditions cover on the owner maintaining the product according to its guidelines, including a minimum six-monthly washing with fresh water of areas not normally exposed to rain. Its technical bulletin tightens that to three-monthly in coastal locations where marine salt spray is prevalent, and in areas with significant airborne dust or industrial fallout.

Unwashed areas means anywhere sheltered from rain: fascia, wall cladding under eaves, garage doors, the underside of eave gutters, carports and patios. Those are exactly the places people never think to wash.

Bushfire Compliance Is About The System, Not The Sheet

Steel is non-combustible, which is why Colorbond is widely used in bushfire prone areas. But non-combustibility of the sheet is not the same as compliance of the roof, and BlueScope's own wording carries the qualifier that marketing copy tends to drop: its products may be used as part of a compliant system in bushfire prone areas, including at BAL-FZ.

Under AS 3959 the whole system has to meet the requirements for your Bushfire Attack Level, including roof and wall junctions, penetrations, gutters, valleys and sarking. At BAL-FZ the roofing system must either follow the generic AS 3959 construction or be a system tested to AS 1530.8.2. BlueScope's own bushfire documentation specifies additional protection at BAL-FZ beyond what is needed at lower levels. And the applicable BAL is determined by your state or territory building authority.

Thermatech Is Real, And Colour Dependent

Thermatech is BlueScope's solar reflectance technology, applied to 21 of the 22 core Classic colours plus the six Matt colours. BlueScope's technical bulletin describes it as enhancing solar reflectance across the colour range and says it is particularly effective on darker colours.

What BlueScope does not publish is a quantified energy saving. Its claim is that the technology is designed to reflect more of the sun's heat on hot sunny days, which can help keep homes cooler in summer, carrying its own footnote that results depend on roof colour, roof shape, insulation, and the type, location, shape and function of the building. We could find no percentage figure, no modelled cooling bill reduction, and no independent CSIRO or peer-reviewed verification.

Thermatech narrows the gap between a dark roof and a light one. It does not close it. If cooling performance is the goal, colour choice still does more work than the technology does.

Choosing The Right Grade, Especially Near The Coast

This is a specification decision with a real cost consequence, and it is the one most likely to be glossed over in a quote.

BlueScope Technical Bulletin TB-01A. BlueScope describes the table as a guide and directs specifiers to contact Steel Direct.

The difference is coating mass. Standard Colorbond uses an AM100 aluminium, zinc and magnesium alloy coated substrate with Activate technology. Colorbond Ultra uses AM150, a 50 per cent heavier coating.

One practical trap: the standard range offers 22 core colours, with six of those available in a Matt finish. Colorbond Ultra comes in seven. If you are coastal and need Ultra, your colour choice narrows considerably, which is worth knowing before you fall in love with a swatch.

A quote that just says "Colorbond" without naming the grade is not comparable to one that does. If you are anywhere near the water, ask which product and why.

Who Is Allowed To Do The Work

Roofing licensing in Australia is inconsistent in a way that surprises most homeowners, and it matters more for metal than for tile.

In Victoria, work on metal roofs can be undertaken only by registered or licensed plumbers, because metal roofing is classed as roof plumbing. In New South Wales, metal roof coverings fall within roof plumbing, which is a licensed trade, with a licence required above $5,000 in labour and materials. In Queensland it is a QBCC roof and wall cladding licence rather than a plumbing licence, required above $3,300. In Western Australia there is no roofing or roof plumbing licence at all.

Every state publishes a public register. Checking takes a minute and is worth doing, particularly given that one of the two recurring failure causes in the WA investigation was work carried out without the required licences.

Whether Your Job Carries Statutory Insurance

Home warranty insurance thresholds vary enough that a Colorbond reroof can land on either side of them.

A $19,000 reroof is covered in Queensland and Victoria and uncovered in New South Wales, Western Australia and South Australia. If your quote is sitting just under a threshold, that is worth raising.

Labour, And Why Quotes Diverge

Labour is typically the larger half of a roofing job, and it is worth understanding what sits underneath a charge-out rate.

Under the Building and Construction General On-site Award, a Level 3 carpenter or roof tiler in residential building has a minimum rate of $30.86 to $31.95 per hour from 1 July 2026. Roof plumbers sit under the Plumbing and Fire Sprinklers Award.

Those are minimum employee wages, not what you pay. The gap covers superannuation, insurance, vehicles, tools, travel, non-billable time and margin. No official source publishes roofing charge-out rates, so treat any hourly figure you see as observation.

Where quotes genuinely diverge is scope. Scaffolding or edge protection, strip-out and disposal, structural allowances, batten replacement, sarking, and the product grade are all decisions that move the number substantially. Two quotes that differ by $8,000 may simply be pricing different jobs.

Removing The Old Roof

Strip-out is a real cost that the per square metre rates exclude, and it is the stage where surprises surface.

Once the old covering is off, the structure is visible, which is the right moment to deal with rot, sagging or inadequate tie-downs rather than covering them up for another thirty years.

If the existing roof is asbestos cement, this changes character entirely. A whole roof is always well beyond the 10 square metre non-friable threshold that allows unlicensed removal, so it requires at minimum a Class B licensed asbestos removalist. And the rule that matters most: never allow anyone to high pressure clean an asbestos roof. WorkSafe Queensland states there is no system of use that can effectively capture or suppress asbestos fibres in those circumstances, and regulators across several states list high pressure water spray among prohibited equipment for asbestos work.

No government or independent body publishes a cost benchmark for asbestos roof removal, so get quotes from licensed removalists.

When To Reroof Rather Than Repair

The honest signals are fairly consistent. Persistent leaks that survive repeated repairs. Widespread rust across an older metal roof rather than isolated spots. Many cracked or slipped tiles rather than a few. Sagging sections, which point at the structure rather than the covering. And repeated repair bills every couple of years, where the money is usually better redirected.

A roof inspection before committing is worth the fee, because it settles the question and because it is the same assessment a tile-to-metal conversion needs anyway.

Frequently Asked Questions

The questions below come up most often once people start comparing quotes.

How Much Does A Colorbond Reroof Cost?

The only independent Australian benchmark, Archicentre's 2026 Cost Guide, puts steel roofing at $60 to $130 per square metre including GST, for covering fixed to an existing roof frame. That excludes strip-out, disposal, scaffolding and framing upgrade, which the guide itself flags separately. No government or consumer body publishes a total figure for a Colorbond reroof, so treat any single number as market observation rather than data.

How Long Does A Colorbond Roof Last?

BlueScope does not publish a service life figure. The widely repeated "up to 50 years" is not traceable to any BlueScope document. The 60 year figure that does appear refers to the duration of BlueScope's testing programme and how long the product has existed, not to lifespan. Warranty is issued project by project depending on product, application and site, so the honest answer is to have your roofer apply for the actual warranty for your address.

Is It Worth Switching From Tiles To Colorbond?

It can be, but treat it as a structural change rather than a change of covering. Removing tile weight increases net wind uplift on the structure, so tie-downs must be reassessed and usually upgraded, and existing tile battens cannot be assumed suitable for sheet roofing. A WA investigation found about half of Perth storm roof losses involved lightweight metal that had replaced tile or asbestos, failing even below the wind speeds standards require. A building permit will likely be required, and an engineer should assess the structure.

Does A Colorbond Roof Need Maintenance?

Yes, and it is a warranty condition. BlueScope requires a minimum six-monthly fresh water wash of areas not normally exposed to rain, reducing to three-monthly in coastal areas with salt spray, or in dusty or industrial locations. Unwashed areas include fascia, cladding under eaves, garage doors and the underside of eave gutters.

Is Colorbond Suitable For Bushfire Prone Areas?

Steel is non-combustible, and BlueScope states its products may be used as part of a compliant system in bushfire prone areas including at BAL-FZ. But the sheet being non-combustible does not make the roof compliant. Under AS 3959 the whole system including junctions, penetrations, gutters, valleys and sarking must meet your Bushfire Attack Level, and at BAL-FZ the system must follow the generic AS 3959 construction or be tested to AS 1530.8.2.

Which Colorbond Grade Do You Need Near The Coast?

BlueScope specifies Classic and Matt finishes for use more than 200 metres from breaking surf, Colorbond Ultra more than 100 metres, and SUPERDURA Stainless from zero metres. Ultra uses a 50 per cent heavier coating. Worth knowing that Ultra comes in seven colours against 22 in the standard range, so coastal sites have a narrower palette.

How Long Does A Reroof Take?

The on-site work is usually short, commonly a few days for a straightforward house. What sets the timeline is everything around it: the building permit if the cladding type is changing, engineering assessment, and licensed asbestos removal if the existing roof is asbestos cement.

Compare Roofing Contractors With Trade Heroes

The short version is that Colorbond is a good product with a marketing layer around it, that the cost figures circulating online are not traceable to anything, and that the tile-to-metal conversion is the part of this job most likely to go wrong in ways you will not see until a storm.

So compare quotes on scope rather than total. Ask which product grade, what happens to the tie-downs, whether an engineer has looked at the structure, whether a permit has been applied for, and what the strip-out and disposal allowance is. Check the licence on your state's register. Check whether the value puts you above or below your state's insurance threshold.

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