The Construction (Design and Management) Regulations 2015 (CDM), apply on all construction projects regardless of size.
CDM governs the Health and Safety of people involved in the design, construction, maintenance and use of buildings, to help make buildings and building sites a safer place for everyone.
If you require more than a single contractor, then you must appoint a Principal Designer.
For a single contractor, think in terms of a single trade, or subcontractor.
To help you meet your legal obligations under CDM, the Principal Designer appointment should be made as early as possible.
