You only need to notify the Health and Safety Executive under the CDM Regulations 2015 if your construction project meets specific legal thresholds set out in the regulations. This notification is made using an F10 notice and is used to inform the HSE that a notifiable construction project is taking place.
A project becomes notifiable if it is expected to last more than 30 working days and have more than 20 workers working on site at any one time, or if it exceeds 500 person-days of construction work in total. Person-days is a way of measuring the total amount of labour involved across the project, calculated by multiplying the number of workers by the number of days worked.
If either of these thresholds is reached, the client has a legal duty to ensure the project is notified before construction work begins. In practice, this responsibility is often managed by the principal contractor or principal designer, but the legal duty remains with the client under CDM 2015.
If a project does not meet these thresholds, it is not classed as notifiable and there is no requirement to inform the HSE. However, CDM Regulations still apply in full, meaning the project must still be properly planned, organised and managed with suitable health and safety arrangements in place. This includes ensuring risks are assessed, safe systems of work are in place, and appropriate documentation is maintained where required.
Most smaller construction projects, including domestic work such as extensions, loft conversions, roofing, and refurbishment projects, will not meet the notification threshold. However, they still fall under CDM and still require appropriate health and safety management to ensure the work is carried out safely.