Skip to main content
Builder.Tools
ToolsPricingFind a BuilderFor TradespeopleBlog
UKUS
Builder.Tools

Practical construction calculators and project tools. 5 tools stay free; the full quotes, jobs and invoices workspace is localized for UK firms.

Tools

  • Calculators
  • AI-Powered
  • Utilities

Company

  • Find a Builder
  • Join Our Network
  • Trade Partners
  • For US Contractors
  • Our Story
  • Blog
  • Help & Support
  • Contact

Legal

  • Terms of Service
  • Privacy Policy
  • Cancellation & Refunds
  • Disclaimer
  • Affiliate Disclosure

© 2026 Builder Tools. All rights reserved.

Need a hand? Help & Support · contact@builder.tools

Built in the UK. Now building for US contractors too.

  1. Home
  2. Tools
  3. CDM Triage

CDM 2015 Trigger Triage

Triage five common CDM 2015 triggers: F10, principal roles, the construction phase plan and health and safety file.

How to use the CDM 2015 Trigger Triage

  1. Choose the commercial or domestic client route and the number of contractors, including subcontractors.
  2. Enter working days, the maximum simultaneous workforce and a separately estimated person-day total.
  3. Review the preliminary F10, principal-role, construction-phase-plan and health-and-safety-file triggers.
  4. Confirm the programme, appointments and full dutyholder responsibilities against current HSE guidance.

Why use this tool

  • Applies the strict F10 boundaries and keeps simultaneous workforce separate from person-days.
  • Shows principal roles and the health and safety file only for projects involving more than one contractor.
  • Includes the construction phase plan, which is required for single- and multiple-contractor projects.

CDM 2015 applies broadly to construction projects in Great Britain. An F10 is triggered when work is expected to last longer than 30 working days and have more than 20 workers simultaneously at some point, or exceed 500 person-days. Projects involving more than one contractor require principal designer and principal contractor roles and a health and safety file; every project requires a proportionate construction phase plan. Domestic client duties normally pass to the contractor or principal contractor, although a principal designer can take client duties by written agreement on a multi-contractor project. This tool triages those five common triggers only and does not identify every duty, Schedule 3 risk, appointment or document requirement.

Part of Builder Tools Utilities — construction tools for UK tradespeople.

Related building tools

  • VAT & CIS
  • T&Cs
  • Invoice