Each commissioner of the revenue shall commence, annually, on January 1, and proceed without delay to ascertain all the real estate in his county or city, as the case may be, and the person to whom the same is chargeable with taxes on that day. The beginning of the tax year for the assessment of taxes on real estate shall be January 1 and the owner of real estate on that day shall be assessed for the taxes for the year beginning on that day.
The commissioner, before making out his land book, shall assess the value of any building and enclosure not previously assessed, found to be of the value of $100 and upwards. The value shall be added to the value at which the land was previously charged.