(3)If no such undertaking as is referred to in sub-section (2) is given or if, in a case where any such undertaking has been given, any work of improvement to which the undertaking relates is not carried out within the specified period or the building is used in contravention of the terms of the undertaking, the Board of Councilors shall forthwith make an order of demolition of the building requiring that the building shall be vacated within such period, not being less than sixty days from the date of the order, as may be specified in the order, and demolished within ninety days after the expiration of that period.
