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How we estimate roof replacement cost

Every estimate combines a national price for each part of the job with a local labor adjustment for your state. Here is exactly how that works and where the numbers come from.

The formula

For each line item we multiply a quantity (driven by your roof area, pitch, number of storeys, material grade, and whether the old roof is removed) 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 / m²ref
Underlayment$5.00 / m²ref
Roofing material$29.00 / m²ref
Installation labor$39.00 / m²ref
Flashing & vents$4.50 / m²ref
Disposal$3.50 / m²ref

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 & 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