Safety (Construction (Design and Management) Regulations):
You may need to advise local Building Control (a Section 80 Demolition Notice) before carrying out demolition. There are some works, particularly small ones where this isn't necessary. the threshold is 1750 cubic feet (just under 50m³). Anything above this volume, unless it's an unattached agricultural building (or one or two other specified types) will be covered by the requirement.
Construction, Design and Management, Regulations.
All demolition and construction works are covered by these regulations. The principle is that buildings and building work should be design to be as safe as possible to construct, alter, extend, use and demolish as possible. There are various roles assigned to the process, the three most important being: Client, Principal designer, & Principal Contractor.
It is assumed that for small, largely domestic works, the Client will have little knowledge or experience of construction, and therefore the other role holders will take on responsibility. Again for small works, the Principal Contractor may take on the Principal Designer's role.
The client is responsible for making sure that adequate resources are available for the safe conduct of the works, and for the other role holders to carry out their duties.
Principal Designers are required to carry out their own design work diligently in connection with any safety related aspects of the overall works, and, where there are other designers contributing to the project, to check their work and be satisfied that their designs meet the safety objectives. It may be that this will involve provision of details of work methods and safety assessments, by the other designers, as part of their submissions.
The Principal Contractor has a similar role once the project moves into the tendering and construction phases. If the original Principal Designer is no longer involved in the project, as is often the case with domestic works, then the Contractor takes on that role as well.
In drafting the legislation the Health and Safety Executive were keen to avoid overly complex and detailed bundles of documents. At best a set of drawings should contain all that is necessary from the designer. It is not necessary to document construction materials and methods that are well known and understood. Only elements that are unusual, or over which extra care that is not apparent is needed, should be documented in greater detail.
At completion of the works, the client should be provided with adequate documentation to show how the building may be safely and efficiently used, and what precautions, if any, are needed when maintaining, altering or demolishing it.
By the very nature of this short explanation, nothing has been covered in much detail and there are elements that have not been mentioned at all. It is intended that this, as all the other guidance on this site is a starting point in understanding the relevant matters.