⌂ RoofingCalculatorHQ

Roof Estimate Calculator (Australia)

Free roof estimate calculator for Australia. Build a contractor-style quote with line-item costs, overheads, profit, contingency and 10% GST — plus a good/better/best 3-tier offer and 30/40/30 progress payments.

Roof Estimate Calculator

Build a contractor-style itemised estimate: direct cost, overhead, profit, contingency and tax — plus a 3-tier good/better/best proposal, crew schedule and draw schedule.

Markup chain (contractor inputs)
Estimated proposal total
$50,728
$226/m² installed · Concrete tile · 24.2 squares
Crew of 4 → ~8.3 working days · 266 labour hours · gross margin 21.1%
Good (basic finish)
$43,626
3-tab / utility-grade
Better (recommended)
$50,728
As specified above
Best (premium)
$59,859
Designer + extended warranty
Itemised line breakdown
Material
$6,842
Labour
$14,752
Tear-off
$3,854
Disposal
$2,259
Underlay
$1,853
Deck repair
$1,026
Code upgrades
$1,998
Permit
$648
Direct cost
$33,233
+ Overhead
$5,982
+ Profit
$4,706
+ Contingency
$2,196
+ Tax
$4,612
Draw schedule (30 / 40 / 30)
Deposit (signing)
$15,219
Midpoint (dry-in)
$20,291
Final (sign-off)
$15,219

How this roof estimate calculator works

Most cost calculators give you a single number. A real Australian builder’s estimate has six layers stacked on top — direct cost, overhead, profit, contingency, GST, and the schedule of progress payments. This calculator shows all six. Enter the building footprint in m², the pitch in degrees, the material, complexity and region, then adjust the markup chain to match the kind of contractor you’re comparing — a local sole trader runs 12% overhead and 10% profit; a national franchise runs 25% and 15%.

The output is a written-quote-style proposal: itemised line breakdown in AUD, three-tier good/better/best, gross margin %, a labour-hour estimate based on crew size, and a 30/40/30 progress-payment schedule.

The contractor markup chain — how the price gets built

direct cost   = materials + labour + strip-out + skip + sarking + battens + ridge fittings + permit
+ overhead    = direct × overhead%        (ute, public liability, insurance, marketing, HSEQ)
+ profit      = (direct + OH) × profit%   (the contractor's net margin)
+ contingency = subtotal × contingency%   (rot / asbestos / termite allowance)
+ GST         = subtotal × 10%
= grand total

The markup is multiplicative, not additive. A 20% overhead on a A$22,000 direct cost is A$4,400, not A$2,200 — which is why a A$28,000 materials-and-labour figure on the back of a survey turns into a A$38,000 final invoice. The markup chain pays the ute, the A$10m public-liability cover, the workers comp premium, the HIA / MBA membership, the slow-month payroll and the 1-in-5 jobs that uncover hidden rot or asbestos.

The math, derived from first principles

slope factor = sqrt(1 + tan(pitch°)²)
roof area    = footprint × slope factor

A 200 m² footprint at a 25° pitch has a slope factor of 1.103, giving a surface of 221 m². Concrete tile material runs about A$32/m² installed, labour about A$48/m² installed; strip-out adds A$18/m² and skip A$10/m². With sarking, batten replacement, dry-ridge and a building permit the direct cost lands around A$22,000.

Apply the markup chain (18% overhead, 12% profit, 5% contingency, 10% GST) and the proposal total comes out to roughly A$33,500 — about 52% above raw direct cost. The GST alone is about A$3,000 of that gap.

Region tier — why Sydney and cyclone-region quotes are 25% higher

TierMultiplierExamples
Low0.85Regional SA, Tasmania, regional QLD/NSW
Mid1.00Adelaide, Brisbane, Perth, Hobart, Canberra
High1.28Sydney metro, Melbourne metro, Gold Coast, Cairns (cyclone region), Darwin

The high-tier multiplier captures higher labour rates (CFMEU enterprise agreements push Sydney/Melbourne wages 18–25% above other capitals), AS 1170.2 cyclonic uplift fastening for region C/D (mandatory cyclone tie-down kits, double-screw schedule, secondary water barrier), AS 3959 BAL-rated materials in bushfire-prone areas (BAL-29 / BAL-40 sarking and ember-resistant ridge requirements), parking permits and CDM-equivalent OH&S overheads. ARC’s 2026 cost survey shows the spread between regional and Sydney/Melbourne pricing is now 28%.

Crew size and labour-hour estimate

The calculator divides labour cost (labour line + strip-out line) by the burdened hourly rate (default A$70/hr — covers wages, super, workers comp, public liability and tooling), then divides by crew size × 8 hours to estimate working days.

A 4-person crew on the 200 m² concrete-tile reroof above pulls roughly 165 labour-hours, so 5 working days. That matches the ARC technical-data benchmark of 35–45 m² stripped and re-laid per crew-day on a moderately complex job. If a competing tender promises completion in two days with a three-person crew, the maths doesn’t add up — they’re either skipping the strip-out properly or not replacing damaged battens.

NCC permit and registration

Per NCC 2022 Volume 2, any reroof that affects structural elements or changes the wind-uplift assembly triggers a building permit through the local Council or a private certifier. The calculator estimates the permit at 3% of materials+labour or an A$650 floor — appropriate for most residential permits including Council inspection. Some states/areas are more expensive:

  • NSW (Sydney CBD, North Shore): Section 10.7 certificate plus Council inspection fees A$800–A$1,400.
  • VIC (Melbourne): Building permit + Building Surveyor + termite inspection A$700–A$1,200.
  • QLD coastal (cyclone region C/D): Form 16 cyclonic compliance certificate from a licensed engineer A$400–A$900 extra.
  • Bushfire-prone areas (NSW BAL, VIC BAL, ACT BAL): BAL assessment plus AS 3959 compliance certificate.

The contractor must hold an appropriate state licence: NSW (NSW Fair Trading), VIC (VBA), QLD (QBCC), WA (Building Commission), SA (Consumer & Business Services), TAS (CBOS), ACT (Access Canberra), NT (NT Building Practitioners Board).

Progress payments — what’s legal in your state

Australia’s eight states and territories each have residential-building consumer-protection legislation that caps deposits and dictates progress-payment intervals:

  • NSW: deposit ≤ 10% of contract price (Home Building Act 1989).
  • VIC: deposit ≤ 5% over A$20,000 (Domestic Building Contracts Act 1995).
  • QLD: deposit ≤ 10% (Domestic Building Contracts Act 2000).
  • WA: deposit ≤ 6.5% on contracts over A$7,500.
  • SA: deposit max A$5,000 or 10%, whichever is less.
  • TAS: deposit max 5%.
  • ACT: deposit max 10%.
  • NT: deposit max A$5,000 + 5%.

Most contractors then progress 40% on dry-in and 30% on completion. The 30/40/30 split this calculator shows is the typical shape but the deposit number must be capped to your state. Always pay by EFT or card with a written tax invoice; never pay cash.

The 3-tier good/better/best

  • Good (86%): concrete tile (Boral, Monier), 25-year manufacturer guarantee, dry-ridge to AS 2050.
  • Better (100%, recommended): Colorbond steel sheet 0.42 BMT (BlueScope Lysaght Custom Orb / Klip-Lok) or concrete tile + sarking + dry-fix ridge, 30-year material + 10-year workmanship.
  • Best (118%): Colorbond Ultra (coastal grade, 25-year corrosion warranty in marine zones), terracotta tile (Wienerberger heritage range) or zinc standing-seam, 30+25-year material+workmanship.

Sources used in this calculator

  • Master Builders Australia (MBA) — 2026 contractor cost index.
  • ARC (Australian Roofing Contractors) — technical bulletins, ridge ventilation guidance.
  • AS 1562.1 — design and installation of metal roofing.
  • AS 2050 — installation of roof tiles.
  • AS 1170.2 — wind actions for buildings (cyclonic uplift schedules).
  • AS 3959 — construction of buildings in bushfire-prone areas.
  • NCC 2022 Volume 2 — Building Code of Australia requirements.
  • BlueScope and Lysaght — Colorbond technical handbooks and BMT specifications.
  • hipages and ServiceSeeking 2026 cost surveys — homeowner-survey medians.

Use this calculator alongside the others

For a single material-cost estimate without the markup chain, use the roof cost calculator. For a low/mid/high consumer cost band with insurance scenarios, use the roof replacement cost calculator. To compare 10 materials side by side at the contractor-bid level, use the roofing cost calculator. When you’ve gathered three real tenders, compare them line by line against this output and ask each contractor to justify any line more than 15% off.

Frequently asked questions

What's the difference between a roofing estimate and a quote in Australia?
An estimate is a non-binding figure based on the information the roofer has at the time of survey. A quotation, once accepted in writing, is a fixed-price contract under Australian Consumer Law (ACL). Master Builders Australia (MBA) and ARC member contractors typically issue a written estimate after the initial inspection and convert to a fixed quote once the roof is exposed and structural condition verified. The number this calculator gives you is in the estimate range — useful for budgeting and comparing tenders.
How much overhead and profit do Australian roofing contractors add?
Most MBA member firms run 16–22% overhead and 10–15% net profit. Sole-trader operators run leaner (10–14% overhead) but limited capacity; large national groups run 25–35% because of marketing, financing and HSEQ overheads. The calculator defaults to 18% overhead and 12% profit. Combined gross margin (overhead + profit) on a healthy job is 28–34%.
Is GST included in the estimate?
Yes — the calculator adds the standard 10% GST on top of the contracted price. GST applies to all roofing services on residential and commercial buildings. Some new-build owner-builders can claim GST credits via the GST property residential margin scheme, but on a typical reroof of an existing home the GST is a final cost. Tax invoices from MBA-licensed contractors must show the GST amount separately per the ATO 'tax invoice' rules.
Why does every Australian roof estimate include a contingency?
Stripping a tile roof in Sydney, Melbourne or Brisbane regularly exposes timber rot, sarking failure, asbestos cement infill (pre-1987) or termite damage in the rafters. ARC's 2026 contractor survey reports 71% of reroofs uncover at least one extra-cost defect. Most contractors price a 4–7% contingency or build a written variation clause into the contract per HIA standard. The calculator defaults to 5%.
Is strip-and-cart-away priced separately?
Yes — strip-out is its own line item because the work is physically different (skip hire, asbestos sampling on pre-1987 cement sheet, manual handling) and because some clients arrange skip hire themselves. The calculator shows strip-out and disposal as standalone lines. Pre-1987 cement sheets can contain asbestos and require a licensed Class B asbestos removalist plus an independent air clearance — budget A$800–A$2,500 extra if the survey hasn't already cleared this.
How does the 3-tier good/better/best work in Australia?
Good is a budget option (concrete tile, 25-year manufacturer guarantee, vented ridge). Better is the specified scope (Colorbond steel sheet 0.42 BMT or concrete tile + sarking + dry-ridge to AS 2050). Best is a premium upgrade (Colorbond Ultra in coastal areas, terracotta tile from a heritage-grade manufacturer, 30+25-year material+workmanship). The calculator approximates each tier at 86% / 100% / 118% of the better total.
What's a normal progress-payment schedule for an Australian reroof?
Most MBA / HIA contracts use 30% deposit on signing, 40% on completion of strip-out and dry-in, 30% on completion and sign-off. Each state caps deposits — NSW Fair Trading caps residential building deposits at 10% of the contract price for jobs over A$20,000; Victoria caps at 5% over A$20,000 (Domestic Building Contracts Act 1995). Always check your state's specific cap before paying more than 10–30% up front. Use a contract that complies with your state's residential building contract requirements.
Why does the same roof cost more in some regions?
The calculator uses three region tiers — low (×0.85), mid (×1.00) and high (×1.28). Low covers regional South Australia, Tasmania, regional NSW/QLD. Mid covers most metro Adelaide, Brisbane, Perth, Hobart. High covers Sydney metro, Melbourne metro, Gold Coast, Cairns cyclone region, Darwin. High-tier zones reflect higher labour rates, BAL-rated material requirements (NSW/Victorian bushfire prone), AS 1170.2 cyclonic uplift fastening (region C/D), parking permits and the licensing overhead that thins the contractor pool.

Related calculators