If you are doing or having construction and building work carried out, you will have health and safety responsibilities to consider before starting work.
If you are having construction work done on your own home, or on the home of a family member that is not done in connection with a business you are a domestic client. CDM 2015 applies to all construction work including domestic projects. As a domestic client your duties under CDM 2015 are passed on to others who are carrying out the construction work on your behalf (such as designers and contractors). Those carrying out the work will also have duties of their own.
If you are having construction work done as part of a trade or business e.g. as a landlord or developer, the work may be notifiable and you will have duties as a commercial client under CDM 2015.
Construction work is notifiable to the HSE if the construction phase is expected to last more than 30 days or 500 person days of construction work.