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Section 79: Planning permission for alteration or extension of building where no office development permit required

Town and Country Planning Act 1971 · 1971 c. 78View on legislation.gov.uk

Part IV: Additional Control in Special Cases

The provisions of this section shall, subject to subsection (4) of this section, have effect with respect to any planning permission for the alteration or extension of a building on land which is within a controlled area when the planning permission is granted and was also within such an area when the application for planning permission was made, but shall have effect only in the case of a building erected under a planning permission granted on or after 1st April 1969.

If the case is the following, that is to say—

either the erection of the building was not development to which these provisions (or Part I of the Act of 1965) applied, or it was such development but no office development permit was required for it; and
either the proposed alteration or extension is not development to which these provisions apply or it is such development but no office development permit is required for it; and
there will result from the proposed alteration or extension a building with an aggregate floor space of twice, or more than twice, the prescribed exemption limit,

the planning permission for the alteration or extension shall be granted subject to the condition specified in subsection (3) of this section (in addition to any other conditions imposed by the authority granting the permission).

The said condition is that the use of the building as altered or extended, or as subsequently further altered or extended, shall be restricted so that (whether in consequence of a change of use or otherwise) it does not at any time contain office premises having an aggregate office floor space which exceeds the prescribed exemption limit.

In the following two cases this section shall not apply—

where the planning permission is in respect of a building which, after its alteration or extension, will be wholly residential; and
where the planning permission is subject to conditions by virtue of section 70(5) or (6) of this Act and those conditions either restrict the office floor space which the building as extended or altered may contain or preclude it from containing any office floor space.

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This legislation text comes from legislation.gov.uk. Contains public sector information licensed under the Open Government Licence v3.0. These source and reuse terms cover the legislation text, not Remedy's commentary.

Reuse reviewed 21 August 2026 under Open Government Licence v3.0.