Roof Stormwater Flow Calculator

Indicative peak roof flow from area and rainfall intensity (rational method lite). Free indicative methodology calculator from constructionmethodology.com.

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📋 Methodology Summary

Free plan: up to 5 calculators per summary PDF/report.

INDICATIVE ONLY — This summary is produced by the Construction Methodology Calculator (constructionmethodology.com) for preliminary methodology planning. Quantities, durations and costs are estimates based on user inputs and rule-of-thumb factors. They are not a substitute for engineering design, quantity surveying or formal tender pricing. Verify all values against project documentation and applicable standards before ordering, pricing or construction.

⚠️ Disclaimer — Indicative Use Only

This calculator is provided by constructionmethodology.com for preliminary construction methodology planning.

  • Indicative only. All quantities, durations, energy figures and costs are estimates derived from user inputs and industry rule-of-thumb factors (waste, bulking, coverage, productivity).
  • Not professional advice. Outputs do not constitute engineering design, quantity surveying, fire engineering, electrical design or financial advice.
  • Verify before use. Confirm all values against project drawings, specifications, geotechnical data, manufacturer literature and applicable standards (e.g. NCC, AS/NZS series) before ordering materials, pricing works or committing to programme.
  • Fire & life-safety values (extinguishers, sprinklers, detectors, egress) are counting aids only — layouts must be designed and certified by qualified practitioners.
  • Rates & currency. Cost outputs simply multiply your entered rates; the currency setting changes the display symbol only, with no exchange conversion.
  • No liability. To the extent permitted by law, no responsibility is accepted for loss arising from reliance on these outputs.
  • Licence & copyright. This calculator and its code, layout and reference data are © constructionmethodology.com. You may use the live tool for project planning. You may not copy, scrape, re-host, resell or white-label it without written permission.

Editable factors (waste %, bulking, coverage, productivity) should always be adjusted to your site conditions.

⚙️ Settings

Changing units converts every input and result live — your entered values are preserved.
Display symbol only — no exchange conversion is applied to values.
Guide rates are rough planning figures only — replace with your tender rates.
Also used for project packs on the Summary tab.

🚚 Include Transport & Haulage?

Calculate trips from the methodology items and place a Transport & Haulage line at the end of the summary.

Edit summary line

Change item name, quantities, cost, notes or method of transport. Lines are kept until you use Clean summary.

Optional on material lines (methodology note). On the haul line this drives capacity presets.