A commencement notice, or in some cases a shorter seven-day notice, is generally needed before starting building work covered by the Building Regulations, such as new dwellings and most extensions involving structural work. The exact threshold depends on the type, floor area and value of the works, so it should be confirmed against the current Building Control Regulations or with your local authority.
The Building Control Regulations set out categories of building work that require a commencement notice, a seven-day notice, or in limited circumstances neither, before construction begins. Broadly, most new dwellings and larger or more complex works require a full commencement notice, which must be lodged a set number of days before works start, along with detailed particulars including drawings and details of the assigned certifier and builder. Certain smaller-scale works, defined by criteria such as floor area and estimated value, may instead qualify for the streamlined seven-day notice procedure, which involves less documentation.
Because these thresholds are specific and can be amended over time, it is not safe to assume a particular project falls into one category without checking the current regulations or getting advice from a competent professional. Works that are very minor, such as certain repairs or maintenance that do not involve structural alteration, may fall outside notifiable building control requirements altogether, but this should not be assumed for anything beyond routine maintenance.
In all cases, the required notice, where applicable, must be lodged and its notice period observed before work physically starts on site; commencing works early or without the correct notice can result in the local authority treating the works as unauthorised for building control purposes.