The following is a brief guide to some of the building regulations you will encounter when building a house in Japan.
This is the building volume-to-land ratio and defines the maximum total floorspace allowed on a block of land. The ratio is expressed as a percentage, eg. 200%. In built-up areas in central Tokyo the Yosekiritsu is high, whereas in suburban and rural areas, the Yosekiritsu will be much smaller. The highest ratio in Tokyo is 1300% which applies to commercial land in the Yurakucho / Marunouchi area around Tokyo Station. Even still, there are buildings that exceed this ratio because they have borrowed air rights from neighboring blocks.
How it is calculated:
Land size: 100 sqm
Maximum floor area: 100sqm X 50% = 50 sqm
It is very important to check this ratio before buying land. Although the simple calculation above can give you a very general idea of the total size of the house, I strongly advise consulting with an architect to get an accurate number as factors such as street width, adding a basement, and so on, can increase of decrease the building size.
For homes, a basement is not included in measurements (so long as it makes up less than a third of the total floor area). This is an option for those wanting to get the most out of their land. Constructing a basement, however, costs more per square meter than building above ground.
Garages are also not included in the yosekiritsu ratio, provided they are less than a fifth of the total building area. This is why you may sometimes see garages that have been converted to either storage or an extra room.
For multi-unit dwellings, such as apartments, common halls and balconies do not count towards total floor area.
Another ratio is “kenpeiritsu” which is the maximum building footprint-to-land ratio. For a 100sqm block of land with a kenpeiritsu of 50%, the building can only cover 50% of the land.
Maximum Ceiling Height
Generally speaking there are no limits on ceiling heights.
For reinforced concrete buildings, there are no limitations provided it is built within the Yosekiritsu guidelines explained above.
Maximum Building Height
The zoning will determine building heights in an area. Low-rise exclusive residential zoned areas have maximum building heights of 10 ~ 12 meters. Kyoto’s historical districts have a maximum building height of 15 meters. These rules apply to both wooden and reinforced concrete structures.
Parts of Tokyo have a maximum building height of 200m due to the flight paths of airplanes using Haneda Airport.
Wooden structures, generally have a height limit of 4 stories. Rules on allowing sunlight and airflow to neighbouring buildings can impact how high you can build.
Stairs and Walls
There are also limits on the height of steps and concrete block walls. For residential homes, the maximum height of each step in a staircase is 23 cm. For elementary schools, the maximum is 16 cm. For a concrete block wall, the thickness should be between 15cm and 2.2 meters. For walls below this level, the height cannot exceed 2 meters.
There are no general rules concerning the maximum depth of basement floors. However, a law passed in 2001 said that land ownership rights in populated areas such as Tokyo and Kansai only extends to 40 meters below ground. This means you cannot build a basement that is more than 40 meters below ground. You also cannot interrupt underground gas and water pipes, or subway lines.
Source: Yomiuri Online x SUUMO