How the estimate is built

Each task carries base hours per unit. Hours are multiplied by rule-driven complexity, the specification tier's install-time factor, a site-access factor and a regional productivity index.

Hourly rates start from published national median wages per trade, multiplied by an employer burden factor of 1.45 (payroll tax, insurance, non-billable time) and the local trade index. Each trade also carries a minimum mobilisation charge so a one-hour job never prices as one hour.

Quantities come from the task's expression, increased by a tier-specific waste factor, then rounded up to the way the product is actually sold (bundles, squares, sheets) with minimum order quantities respected.

Unit costs are tiered Good / Better / Best and adjusted by a bounded regional material multiplier. Sales tax and delivery are separate lines, never buried in the unit cost.

Permits, inspections, equipment hire, disposal and protection are allowances gated by rules, scaled by local permit and disposal indices.

Contractor overhead and profit is applied once, as a visible line, in a band that narrows as job size grows: 25% / 21% / 17% at increasing project sizes. Contingency starts from a project base and rises with activated risk rules, capped so it can never dominate the total.

Confidence scores location data quality, how completely conditions were answered, and how much concealed risk the scope carries. The band sets a minimum displayed spread: roughly ±12% at High, ±20% at Moderate and ±32% at Preliminary.

National-average estimates are capped at Preliminary by design. A thinly specified project cannot render a tight number.