(1) Every building shall be assessed together with its site and other adjacent premises occupied as appurtenances thereto unless the owner of the building is a different person from the owner of such site or premises.
(2) The rateable value of a building or land shall be deemed to be the gross annual rent at which such building or land may at the time of assessment reasonably be expected to let from month to month or from year to year less a deduction in the case of buildings only of sixteen and two thirds per cent of such annual rent and the said deduction shall be in lieu of all allowances for repairs or on any other account whatever:
Provided that,-
(a) in the case of,-
(i) any Government or railway building; or
(ii) any building of a class not ordinarily let, the gross annual rent of which cannot in the opinion of the Commissioner be estimated,
the rateable value of the premises shall be deemed to be six percent of the total of the estimated market value of the land at the time of assessment and the estimated cost of erecting the building at such time after deducting for depreciation a reasonable amount which shall in no case be less than ten percent of such cost, and
(b) machinery and furniture shall be excluded from valuations under this section.