Section 21(1) in Tamil Nadu Combined Development and Building Rules, 2019
(1)Executive Authority of Local Body may by written notice, order any building or any portion thereof to be vacated forthwith or within the time specified in such notice;-(a)if such building or portion thereof has been unlawfully occupied in contravention of these Rules(b)if a notice has been issued in respect of such building or part thereof requiring the alteration of restriction of any works specified in such notice have not been commenced or completed.(c)if the building or part thereof is in a ruinous or dangerous condition, which are likely to fall and cause damage to any person occupying, resorting to or passing by such building or structures or any other structure or place in the neighbourhood thereof.
