About Regulations at the time of Construction

Continuing from yesterday, we will explain the building coverage ratio and floor area ratio in the Building Standards Act. This rule explains how large a building can be built for the size of the land. Also, the size of a building that can be built will change depending on how the land exists in the area.

Floor-area Ratio and Building Coverage Ratio Regulations in Land Use Zones

Category of Land Use Zone	Maximum floor-area ratios（％）	Maximum building coverage ratios（％）
Category I exclusively low-rise residential zone	50 60 80 100 150 200	30 40 50 60
Category II exclusively low-rise residential zone	50 60 80 100 150 200	30 40 50 60
Category I mid/high-rise oriented residential zone	100 150 200 300 400 500	30 40 50 60
Category II mid/high-rise oriented residential zone	100 150 200 300 400 500	30 40 50 60
Category I residential zone	100 150 200 300 400 500	50 60 80
Category II residential zone	100 150 200 300 400 500	​50 60 80
Quasi-residential zone	100 150 200 300 400 500	50 60 80
Rural residential zone	50 60 80 100 150 200	30 40 50 60
Neighborhood commercial zone	100 150 200 300 400 500	60 80
Commercial zone	200 300 400 500 600 700 800 900 1000 1100 1200 1300	80
Quasi-industrial zone	100 150 200 300 400 500	50 60 80
Industrial zone	100 150 200 300 400	50 60
Exclusively industrial zone	100 150 200 300 400	30 40 50 60

There are also regulations for roads and neighboring areas as follows.
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​Restrictions on Building Shape in Land Use Zones
【Slant plane Restrictions】
The restrictions limit building heights in proportion to the distance from the other side of the boundaries of the roads they face, or from the adjacent site boundaries. It ensures adequate space for light and ventilation between buildings or on roads.
＊This Slant Plane Restrictions do not apply to buildings which can secure levels of lighting and ventilation equivalent to or higher than those under this restriction.

【Restriction on floor-area ratio according to the width of the adjoining road】
The maximum floor-area ratio of a building site which has a road in front less than １２m wide, shall not exceed the value obtained by multiplying the width of the road in meters by a certain ratio (for residential Land Use Zones, this ratio is 0.4*, for other zones, it is 0.6* ).
* A factor of 0.6 for residential Land Use Zones and 0.4 or 0.8 for other Land Use Zones can be adopted in those zones where such factors are designated by the local government building authority with the approval of the City Planning Council.

【Shadow Restrictions】
These limit the height of buildings so as to ensure sufficient sunlight in residential Land Use Zones, etc. The minimum number of hours per day that the shadows of building sites fall outside the area are specified by bylaws of the local governments according to the Building Standard Law.

The above are the main points to keep in mind when constructing a new building. Therefore, while confirming the details with the architect, the maximum floor area, building height, angle, etc. will be decided.