HomeReno Cost

Methodology and sources

How we estimate roof replacement cost

Every estimate combines national unit costs with a local labor adjustment for your state. This page shows the formula, source inputs, limitations, and review notes behind the calculator.

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6
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8
states
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sources

Methodology summary

Transparent formula

Quantities are driven by your roof area, pitch, number of storeys, material grade, and whether the old roof is removed; the project band is ±15%.

Regional labor only

Labor multipliers affect the labor share of each line item; materials stay nationally priced.

Clear limitations

These are planning estimates, not live contractor quotes or guarantees.

The formula

For each line item we multiply a quantity by a national unit cost, then apply a quality-grade factor. A regional labor multiplier is applied to the labor portion only; materials are priced nationally. We show the itemized result as a ±15% range.

National unit costs

Line itemNational unit costSource
Tear-off$12.00 / m²source
Underlayment$5.00 / m²source
Roofing material$29.00 / m²source
Installation labor$39.00 / m²source
Flashing & vents$4.50 / m²source
Disposal$3.50 / m²source

Regional labor multipliers

Each state's labor multiplier is its private-sector all-industry full-time adult ordinary-time weekly earnings relative to the national private-sector mean, from ABS Average Weekly Earnings (November 2025, Table 14, by state) — used as a proxy for roofing labour because Australia publishes no roof-tiler-by-state (ANZSCO 821211) earnings series in public form, and the private-sector cut strips out the public-service distortion that inflates all-industry figures in the ACT. Multipliers are bounded to a sane range and applied to the labor share of each line item, so materials stay nationally priced while labor tracks local wages.

Data vintage and limitations

Compiled June 2026 from public cost aggregators and government wage data. These are derived estimates, not live contractor quotes. Local prices vary with project complexity, access, and material availability; always confirm with a licensed contractor before budgeting.

Sources