3.—(1) In these Regulations “building work” means—
(a)the erection or extension of a building;
(b)the provision or extension of a controlled service or fitting in or in connection with a building;
(c)the material alteration of a building, or a controlled service or fitting, as mentioned in paragraph (2);
(d)work required by regulation 6 (requirements relating to material change of use);
(e)the insertion of insulating material into the cavity wall of a building;
(f)work involving the underpinning of a building;
(g)work required by regulation 22 (requirements relating to a change of energy status);
(h)work required by regulation 23 (requirements relating to thermal elements);
(i)work required by regulation 28 (consequential improvements to energy performance).
(2) An alteration is material for the purposes of these Regulations if the work, or any part of it, would at any stage result—
(a)in a building or controlled service or fitting not complying with a relevant requirement where previously it did; or
(b)in a building or controlled service or fitting which before the work commenced did not comply with a relevant requirement, being more unsatisfactory in relation to such a requirement.
(3) In paragraph (2) “relevant requirement” means any of the following applicable requirements of Schedule 1, namely—
Part A (structure)
paragraph B1 (means of warning and escape)
paragraph B3 (internal fire spread—structure)
paragraph B4 (external fire spread)
paragraph B5 (access and facilities for the fire service)
Part M (access to and use of buildings).