Japanese Building Code Basics

When considering buying property for personal use or investment purposes, owners must be aware of the building codes and regulations that exist here in Japan. While in general, you may find some codes to be the same as your home country, there may be some special rules unique to Japan. Regardless, lets take a look at some of the most important building codes in Japan.

1. Safety according to the Building Standards Law

Buildings must be structurally safe for proper use. This means that buildings may not collapse or suffer significant damage simply by daily use. Buildings also must not be constructed by means that will lead to severe damage due to aging or standard wear-and-tear. Expanding on this, many buildings in Japan need be structurally durable to fires, earthquakes, and severe weather. Many buildings in Japan are constructed with earthquake safety in mind, as there are many earthquakes here. However, thanks to modern safety standards, many buildings suffer little to no damage in the case of most earthquakes. Aside from being structurally sound, there must be sufficient emergency evacuation routes clearly marked in all buildings.

2. Sanitary standards

All buildings must be built on higher ground than the surrounding land that they were built on. This type of structure allows for the ensuring of proper draining and the prevention of water-related trouble such as flooding or damage due to damp land underneath the building. Japan gets a lot of seasonal rain in both the spring (known as Tsuyu) and late summer/early autumn (due to typhoons). Therefore, it is important to insure your home or commercial property in Japan is equipped for draining water and directing sewage properly.

3. Structural configurations

New buildings must follow a strict set of plans that adhere to safety regulations and building methods. Specific plans for certain types of building aspects, such as cross beams and reinforced framing must be followed. Factors such as type of material used, height, thickness, number of floors or rooms, and stress durability will be important to take caution of when building a new structure on any type of land. With the right architect and building team, they will be sure to follow these rules in order to meet code regulations and create a safe and sound structure.

4. Area-based restrictions

When buying property, you must be aware of the several layers of restrictions that are on a single building or plot of land. In addition to national laws that maintain safety standards, there are also regulations based on what zone, area, and district your property is located at. These restrictions are not the same everywhere, so if buying multiple properties, make sure to be aware of what differences in building codes may exist.

5. Building coverage ratio

In Japan, a bit of a tricky regulation known as Kenpeiritsu (建蔽率 – けんぺいりつ) exists. If you buy a property that is 100m2, you are not necessarily allowed to build on all 100m2 of that land. The acceptable building coverage ratio will be different depending on where you buy property, but as a general rule, dividing the building coverage area by the land area then multiplying by 100 will generate the building coverage ratio. This rule helps maintains safety standards and controls the look of neighborhoods, preventing overcrowding in areas such as the already-crowded Tokyo.

6. Floor area ratio

In addition to Kenpeiritsu, a regulation called yousekiritsu (容積率 – ようせきりつ) is also something to consider when buying or building in Japan. This regulation limits the maximum amount of floor space you can have in a house or other building. As with the previously mentioned building coverage ratio, the acceptable floor area ratio is also determined based on where the land or property is located in Japan. The acceptable floor area ratio will equal the total floor area divided by the site area and multiplied by 100. If a certain area has an 85% allowed floor area ratio, you can split this number in between floors, such as 1 floor having 50% floor area and a 2nd floor having the remaining 35%. It can also be split any other way you prefer (such as 45% and 40%) as long as it is within the limit.

While we have only touched upon a few of the many building codes that exist in Japan, there are many other online resources that detail all of the codes in English. You can visit the Building Center of Japan’s website to find a free English pdf of all the laws and regulations for buildings. If you cannot find the answer to your question, you can also send us an email!

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