When is a construction project notifiable to HSE?
Under CDM 2015, certain construction projects must be notified to HSE using an F10. Notification is a threshold test—it does not decide whether CDM applies or whether the project needs appointments, planning and a construction phase plan.
Reviewed 14 September 2026 · By Lloyd GodsallThe two F10 notification thresholds
A construction project is notifiable if the construction work is scheduled to:
- Last longer than 30 working days and have more than 20 workers working simultaneously at any point; or
- Exceed 500 person-days of construction work.
The tests are alternatives. A project only needs to meet one of them. The first test requires both duration and the peak number of simultaneous workers to be exceeded.
Simple examples
- A 35-working-day project with a peak of 25 workers meets the first threshold.
- A 100-working-day project with a peak of 10 workers does not meet the first threshold, but 1,000 person-days would meet the second.
- A 20-working-day project with 30 workers does not meet the first threshold. Its person-days still need to be checked against the second.
Do not use the F10 test as the CDM test
CDM duties apply far more widely than notifiable work. Every construction project needs proportionate planning, and every project needs a construction phase plan before the construction phase begins.
Who submits the F10?
The client is responsible for notifying HSE as soon as practicable before the construction phase begins. The notice must contain the required project particulars and be updated when necessary. Domestic-client arrangements are different because their duties normally pass to other project dutyholders, so the appointment structure should be checked before deciding who completes the notification.
What does notifiability not change?
Whether or not a project reaches the F10 thresholds, the project still needs suitable management arrangements. If it involves, or is likely to involve, more than one contractor, the client must appoint a principal designer and principal contractor in writing. A construction phase plan is required before construction starts, and welfare must be available from the outset.
Information needed before checking the threshold
- Planned construction start and finish dates
- Working days rather than calendar duration alone
- Expected peak number of workers on site at the same time
- Estimated total person-days across contractors and subcontractors
- Number of contractors and the dutyholder appointment structure
- Changes to programme, workforce or scope that could alter the calculation
Official guidance and related checks
Use HSE’s F10 notification guidance and online form, together with regulation 6 of CDM 2015 for the legal notification requirements.
Then check the wider arrangements with the CDM client duties checklist, principal contractor duties guide and construction phase plan guide. For project-specific help, see CDM support.