How accurate are these time estimates?

Base durations represent typical jobs in standard conditions. Actual times vary with property age, access difficulty, specification level, and unforeseen issues. Always add contingency - experienced tradespeople typically add 15-25% to their estimates.

How does adding workers affect duration?

Adding workers does not halve the time due to coordination overhead, sequencing constraints, and shared workspace limitations. A second worker might save 30% of time, a third saves less again. The calculator uses diminishing returns to model this realistically.

Should I include inspection waiting time?

Yes, for regulated work. Building control inspections can add 1-3 days per visit (typically 4-6 visits for an extension). Electrical Part P notifications need inspection before energising. Gas Safe registrations need completing before handover.

How do weather delays affect outdoor work?

For external work (roofing, brickwork, rendering), expect 1-2 lost days per week in winter months. Concrete and mortar cannot be laid in freezing conditions. External decorating needs dry weather. Budget more contingency for autumn/winter starts.

What if my job is not in the list?

Select "Custom Duration" and enter your own base estimate in working days. The calculator will still apply scope, worker, and delay adjustments to give you a more realistic completion estimate.

TradeCalculator

Job Completion Calculator

Estimate how long a trade job will take based on scope and conditions

Job Type

Scope / Complexity

Number of Workers

How We Calculate This

Select a job type to get a base duration from typical UK trade timescales. The scope selector adjusts for simple (0.75x), standard (1x), or complex (1.4x) versions. Multiple workers reduce duration with diminishing returns. Start delays, weather days, and inspection waiting periods are added on top to give a realistic total working days and calendar days estimate.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.