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Is there an obligation to commence all dwellings on a multi-unit development within the commencement window?


A Commencement Notice must be submitted not less than 14 and not exceeding 28 days before works are due to commence. The local authority has 7 days to validate this.

Once validated, works must commence within the 28-day period – typically 7-10 days after validation. A multi-unit project, even of modest size, would not find it possible to begin work on each and every unit within that period.

Once the builder can point to some work undertaken in furtherance of meeting any Building Regulations within the statutory period, the development has officially commenced. There is no statutory period within which a development (or any element, phase, or unit of it) must be completed.

The Building Control Regulations 1997-2015, Article 8 refers specifically to ‘works’; therefore it can’t be argued that the Commencement Notice can only refer to a building and not a site.

Meanwhile if, for example, a Commencement Notice referred to 65 houses and was validly commenced with 19 houses completed to date and ancillary works for all 65 units undertaken, a further Commencement Notice is not required for the remaining houses at this stage.


If you are in any doubt, contact your local Building Control Authority.

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