Lapse of sanction after one year from the date of such sanction.

Every sanction for the erection or re-erection of any building shall remain in force for one year only from the date of such sanction or for such longer period as the Commissioner may have allowed when conveying sanction under section 256. If the erection or re-erection of the building is not commenced within one year and not completed within two years or

fresh sanction under forgoing provisions of this Act.