If you are planning to carry out 'Building Work' then it must comply with the Building Regulations. This normally means seeking approval of the work from a Building Control Body.
Building Control generally operates as a two-stage process, referred to as the Full Plans application. The first stage (known as the plan stage) involves the applicant submitting detailed plans for approval. These plans are very carefully checked by a Building Control Officer to ensure that all necessary information is shown, and that it complies fully with the Building Regulations. Wherever possible, applicants are given the opportunity to make amendments (if required) before either an approval, conditional approval or rejection is given.
The second stage (inspection stage) starts when work commences on site after which a series of site visits are made to check that the work proceeds in accordance with the plan, and hence complies with the regulations.
The following types of project amount to 'Building Work':
The erection or extension of a building
An alteration project involving work which will temporarily or permanently affect the ongoing compliance of the building, service or fitting with the requirements relating to structure, fire, or access to and use of buildings
When installing replacement windows using a Builder or window company not FENSA registered
The installation or extension of a service or fitting which is controlled under the regulations
The insertion of insulation into a cavity wall
The underpinning of the foundations of a building
When you want to change the building's fundamental use
If your building work consists only of the installation of certain types of services or fittings (e.g. some types of drain, fuel burning appliances, replacement windows, WCs, and showers) and you employ an installer registered with a relevant scheme designated in the Building Regulations (a competent person), that installer may be able to self-certify the work. Therefore, you will not need to involve a Building Control Service. However, this concession is strictly limited to the specific type of installation described and does not cover any other type of building work.