8 Loss of exemption
1 A structure which is an exempt structure by virtue of regulation 6 above shall cease to be an exempt structure if—
(a) any requirement of a notice under regulation 9 below is not complied with within the period stated in the notice; or
(b) at any time on or after 1st March 1991 it is substantially enlarged or substantially reconstructed unless a contract for the work was entered into or the work was commenced before that date and in either case the work was completed before 1st September 1991.
2 The exemption conferred by regulation 7 above shall cease if any requirement of a notice under regulation 9 below is not complied with within the period stated in the notice.
3 Any reference in paragraphs (1) and (2) above to the period stated in a notice is to that period as extended if it has been extended under regulation 9(4) below or by virtue of regulation 10(5) below; and any reference in those paragraphs to a requirement of a notice is to that requirement as modified if it has been modified under regulation 9(4) below.