Under the Construction (Design and Management) Regulations 2015 (CDM 2015) a construction phase plan is required for every construction project. This does not need to be complicated. If you are working for a domestic client, you will be in control of the project if you are the only contractor or the principal contractor. You will be responsible for: n preparing a plan; n organising the work; and n working together with others to ensure health and safety. You could be a builder, plumber or other tradesman, doing small-scale routine work such as: n installing a kitchen or bathroom; n structural alterations, eg chimney breast removal; n roofing work, including dormer windows; n extension or loft conversion. A simple plan before the work starts is usually enough to show that you have thought about health and safety. If the job will last longer than 500 person days or 30 working days (with more than 20 people working at the same time) it will need to be notified to HSE and it is likely to be too complex for this simple plan format.
Source of information: http://www.hse.gov.uk/pubns/cis80.pdf