Section 12(3)(b) in The Tamil Nadu Buildings (Lease and Rent Control) Act, 1960
(b)on the ground specified in clause (b) of sub-section (1), unless the landlord gives an undertaking that the work of demolishing any material portion of the building shall be substantially commenced by him not later than one month, and shall be commenced by him not later than one month, and shall be completed before the expiry of three months from the date he recovers possession of the entire building or before the expiry of such further period as the authorized officer may, for reasons to be recorded in writing, allow.