If you are having construction work done on your own home, or on the home of a family member, as a domestic client you do not have to notify the work to Health and Safety Executive and you will not have duties under Construction (Design and Management) Regulations 2007 - although those doing the work on your behalf (such as designers or contractors) will.
If it is part of a trade or business then you will need to notify them. See the HSE website for more info.
Of course you have the normal duties of care which include making sure that the site is properly fenced in and has the appropriate notices displayed. See Site safety / Security