Where a local authority, on consideration of an official representation or a report by the proper officer or other information in their possession, are satisfied that any building comprises only a house which does not meet, or houses which do not meet, the tolerable standard and that the house or, as the case may be, houses, ought to be demolished, they may, subject to section 119, make a demolition order requiring—
(a)that the building shall be vacated within such period as may be specified in the order, not being less than 28 days from the date on which the order comes into operation, and
(b)that the building shall be demolished within 6 weeks after the expiration of that period or, if the building is not vacated before the expiration of the period, within 6 weeks after the date on which it is vacated.