# Town and Country Planning Act 1971, Paragraph 3


The enlargement, improvement or other alteration, as often as occasion may require, of any such building as is mentioned in paragraph 1(a) or (b) of this Schedule, or any building substituted for such a building by the carrying out of any such operations as are mentioned in that paragraph, so long as the cubic content of the original building is not increased or exceeded—
(a) in the case of a dwellinghouse, by more than one-tenth or 1,750 cubic feet, whichever is the greater ; and
(b) in any other case, by more than one-tenth.

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Source: https://www.legislation.gov.uk/ukpga/1971/78/schedule/8/paragraph/3 (the official version)
Page: https://openlegislation.uk/town-and-country-planning-act-1971/schedule-8/paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.