Original data include number of buildings as well as floor area by typology and building year. Description of original data is below (in Finnish).
Unit conversions from floor areas to tonnes are described in the attatched word document (Mikkelin rakennusranta_yksikönmuunnokset.docx ) (in Finnish).

116g -- Buildings by use and year of completion, 2019

The statistics use the regional breakdown of 1.1.2020.
As a rule, the building stock does not include summer cottages and agricultural buildings (summer cottages are included in a separate table).
The purpose for which a building is classified in a category is mainly determined by the use to which the majority of the floor area of the building is put. Since the 2000 statistics, the criteria for the statistical classification of buildings have been changed so that permanently occupied recreational buildings have been classified as detached houses in the category of residential buildings. Changes in the heating system made without a renovation permit may not necessarily be transmitted to the building control authorities and thus not included in the statistics.

The statistics on buildings and summer cottages are annual statistics and describe the existing stock of buildings and summer cottages on the last day of the year. The building stock does not include lightweight shelters and stands, buildings used exclusively for agricultural production, or residential sauna and utility buildings. Summer cottages are also excluded. A summer cottage is a recreational building built on a permanent site or a residential building used as a holiday home. Commercial holiday homes, holiday village buildings and mobile garden sheds are not counted as non-residential buildings. Statistics on buildings and holiday homes can be produced at all municipal and coordinate-based regional divisions and by postal code area. The data on buildings and summer cottages are mainly provided to Statistics Finland by the Population Information System of the Population Register Centre, to which the building control authorities of the municipalities report data on buildings subject to building permits. The statistics on buildings and summer cottages are aggregated data.

Suomen virallinen tilasto (SVT): Rakennukset ja kesämökit [verkkojulkaisu].
ISSN=1798-677X. Helsinki: Tilastokeskus [viitattu: 15.4.2021].
Saantitapa: http://www.stat.fi/til/rakke/meta.html