The average size of dwellings is obtained by dividing the total floor area of dwellings by their number.

A building refers to any independent structure permanently constructed or erected on its site. It has its own entrance and contains covered space intended for different purposes, usually enclosed within outer walls or walls separating it from other structures (buildings).

Caves and other subterranean spaces which are mainly enclosed within rock or similar walls and/or which do not contain structures comparable to the interior structures of buildings proper, such as underground oil tanks, are not buildings.

Buildings do not include light-structured stalls, kiosks and the like, which do not include spaces separated by closed walls, or transportable caravans, ships and so on.

The building data derive from the building information system maintained by the Finnish Environment Institute Syke.

The building stock statistics of Statistics Finland do not include:

- liquid storage buildings
- buildings used only in agricultural production
- sauna buildings belonging to residential buildings
- outhouses of residential buildings
- buildings entirely controlled by foreign missions
- buildings of the Finnish Defence Forces,
- air raid shelters

except where the above-mentioned buildings are occupied or have commercial properties.


The data on new production of buildings do not include:

- buildings entirely controlled by foreign missions
- buildings of the Finnish Defence Forces
- air raid shelters

The building material refers to the material from which the vertical supporting structures of the building are mainly made. The classification is as follows:
- concrete, light concrete
- brick
- steel
- wood
- other, unknown.

A dwelling refers to a room or a suite of rooms which is intended for year-round habitation; is furnished with a kitchen, kitchenette or cooking area; and has a floor area of at least 7 square metres. Every dwelling must have its own entrance. A single-family house may be entered through an enclosed porch or veranda. If a dwelling is entered through the premises of another dwelling, it is not regarded as a separate dwelling but instead those two constitute one dwelling.

Dwelling density is the ratio between the size of the dwelling and the number of persons living in it. Dwelling size is expressed either as the number of rooms or as the floor area of the dwelling.

Dwelling units are classified according to their occupancy status into dwellings permanently occupied, dwellings temporarily occupied and dwellings not in residential use:

- A dwelling is considered permanently occupied if according to the Population Information System of the Population Register Centre it is permanently occupied by one or more people.
- A dwelling is considered temporarily occupied if according to the Population Information System of the Population Register Centre it is occupied by temporary but not permanent residents.
- A dwelling is not in residential use if according to the Population Information System of the Population Register Centre it is not occupied by either permanent or temporary residents.

The Population Information System of the Population Register Centre's buildings and dwellings data include details on units that in reality are not in residential use or that are incorrectly registered. Such dwellings are not included in the dwelling stock statistics in cases where it has been possible to infer that they are errors or that they should be removed on the basis of other information.

Data on the facilities of dwellings and buildings are derived from the dwelling and building data of the Finnish Environment Institute.

The facilities in a dwelling:
- sewage
- running water
- toilet
- hot water
- washing facilities (shower, bathroom or sauna)
- sauna in the dwelling
- central or electric heating.

The data on a dwelling’s facilities have been used in determining the standard of facilities in the dwelling.

Facilities in a building:

- electricity
- sewage
- running water
- hot water
- lift
- sauna in the building
- mechanical ventilation
- air raid shelter.

The floor area of a dwelling is measured from the inner surfaces of its walls. The figure includes the floor areas of the utility room, walk-in cupboard, bathroom, hobby room, sauna, washroom and dressing room, as well as the floor areas of rooms used for working unless used by hired employees.

The following are not counted in the dwelling's floor area: garage, cellar, sauna facilities in an unfurnished basement, unheated storage space, balcony, porch, veranda and attic space unless used as a living space.

The floor area of a freetime residence refers to its gross floor area.

Heating system refers to the main method of heating used in the heating of a building. Data on the heating system are also available for dwellings. Data on the heating system have been obtained from the building information system maintained by the Finnish Environment Institute Syke, which receives them from municipal building supervision authorities by way of building project notices. Information about a change in the heating system of a building is transmitted to the system only if the modifications in question have required a building permit.

The classification is as follows:
- central water heating
- central air heating
- electric heating
- oven-fireplace-stove heating
- solar heating
- air source heat pump
- no fixed heating installation
- unknown.

In a water central heating system, the building is heated with circulating water, and in an air central heating system, with circulating air. In direct electric heating, the building is heated with the aid of a fixed radiator, etc. connected directly to the electricity network.

In stove heating, heating takes place by burning wood or other fuels in a fireplace (stove) that stores heat. Stove heating also includes electric heating reservoirs, separate fixed oil heaters and heat preserving fireplaces (not lightweight). Stoves used for heating saunas are not regarded as heating equipment.

A kitchen is a room furnished for cooking. A space furnished for cooking measuring less than 7 square metres is a kitchenette or cooking area.

The occupancy rate and standard of equipment of the dwelling together describe the level of housing of the household-dwelling unit.

The classification of occupancy rate:
- Spacious: a household-dwelling unit of one to five persons with room units at its disposal exceeding the number of its members by at least three (kitchen is not included in the number of rooms).
- Overcrowded: more than one person per room unit (kitchen is not included in the number of rooms).
- Normal: not belonging to the above categories.

(Kitchen is not included in the number of rooms from 1989 onwards.)

Standard of equipment:
- High standard of equipment: the dwelling has running water, sewage, hot water, toilet, washing facilities (shower, bathroom or sauna) and central or electric heating.
- Low standard of equipment: the dwelling lacks washing facilities and/or central or electric heating.
- Substandard level of equipment: the dwelling lacks one of the following facilities: running water, sewage, hot water or toilet.

As from 2005 only "High standard of equipment" and "Other or unknown level of equipment" are used.

The following network connections are identified for a building:
- sewage
- running water
- electricity
- natural gas.

The number of storeys in a building consists of all storeys that are primarily above ground level and in which there are habitable rooms or office space or other space conforming to the intended use of the building. If the number of storeys varies in different parts of the building, the number usually refers to the largest number of storeys in the building.

For buildings completed after 1980, the number of storeys is expressed as an average number that takes into account the whole building if the share of the gross floor area of a certain storey out of the gross floor area of the main storeys is very small. For instance, if a large industrial unit is mainly a one-storey building, but office space is located on three storeys, then the number of storeys is given as one.

According to the norms below, a dwelling is over-crowded if it has
- Norm 1: more than two persons per room, with kitchen included in the number of rooms
- Norm 2: more than two persons per room, with kitchen excluded from the number of rooms
- Norm 3: more than one person per room, with kitchen included in the number of rooms
- Norm 4: more than one person per room, with kitchen excluded from the number of rooms.

The norms applied in the statistics have changed over the decades. Norms 1 and 2 were used in the 1970 and 1975 population censuses. Data based on norm 3 have been produced since 1980. Norm 4 was first introduced in the 1990 census. Norm 4 has also been used in the level of housing classification since the 1990 census. Prior to that norm 3 was used.

A residential home refers to a building intended for dormitory accommodation. Residents share the same kitchen, living lounge and/or washing facilities. This type of residential home does not normally have separate dwelling units proper.

In terms of structural engineering a residential home hardly differs from an accommodation building. A residential home is intended for specific groups of people, such as the elderly, disabled, etc. Ordinary residential dwellings built for these groups with no special uses of space (communal kitchens, etc.) are not residential homes.

A dwelling unit within a building classified as a residential home is regarded as a normal dwelling if the dwelling has
- more than one room, including kitchen,
- a kitchen or kitchenette,
- toilet, and
- shower, bath or sauna.

Dwellings in residential homes are not classified as a separate category, but they are counted as part of the regular housing stock. Dwellings in residential homes that do not meet the above conditions are not included in the dwelling stock statistics.

A room is a space with one or more windows that has a floor area of at least 7 square metres and an average height of at least 2 metres. A hall, porch, bed recess, etc. are not counted as rooms. Kitchen is not normally counted in the number of rooms.

The standard of facilities is described with two categories:

- a dwelling with a high standard of facilities the dwelling has running water, sewage, hot water, toilet, washing facilities (shower/bathroom or sauna) and central or electric heating
- other or unknown standard of facilities

Municipal sub-areas are formed of operationally functional wholes defined by the municipality itself, which are the basis of the municipality's regional planning and monitoring. Statistics Finland is responsible for digitising new sub-area boundaries and for maintaining name files. Municipalities have the opportunity to check their sub-area division once a year.

The division into sub-areas is a hierarchical three-level classification which has a 1-digit major area level, a 2-digit statistical area level and a 3-digit small area level. Sub-areas are numbered consecutively using these three hierarchical levels. The 6-digit sub-area code is bound to the 3-digit municipality code, so the sub-area code consists of a total of nine characters.

Dwellings are classified according to tenure status as follows:

Owner-occupied dwelling
- occupant of the dwelling owns the house
- occupant of the dwelling owns shares in housing corporation

Rented dwelling
- rented dwelling subsidised by the State
- rented dwelling with interest support loan
- other rented dwelling

Right of occupancy dwelling

Other tenure status
- e.g. life annuity, kinship

Tenure status unknown

In the dwelling stock statistics the tenure status is mainly defined for permanently occupied dwellings.

Dwellings are classified according to the type of building as follows:

- one to two-dwelling houses: one to two-dwelling houses and permanently occupied free-time residences
- terraced houses: detached houses with at least three adjoining dwellings and where the spaces belonging to different dwellings are not on top of each other.
- blocks of flats: residential buildings of at least three dwellings in which at least two dwellings are located on top of each other and which do not belong to the categories above
- other buildings: also buildings whose type of building is unknown.

The year of construction refers to the year in which the building was completed and was ready for use. If the building was completed prior to 1980, the year of renovation may have been entered as the year of construction.