Building Control in Japan

by HASEGAWA Tomohiro
日本の建築規制 長谷川知弘
Ver. 1910‐ Part B ‐‐ Table of Contents and Abbreviations‐ Part A

Building Control System in General‐ Part B Background Information
Chapter 3 Background
Chapter 4 Local Authorities in Japan
Chapter 5 Structure of Legal Documents on Building Control‐ Part C

Building Regulatory System‐ Part D

Technical Requirements for Building Safety and Amenity (Group A)‐ Part E

Technical Requirements from the viewpoint of City Planning (Group B)‐ Part F

Technical Requirements from the viewpoint of Land‐development (Group C)‐ Annexes (under construction)
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Chapter 3Background on Cities and Architecture2

Geography○○

Inhabitable land is very limited.
Population and economic activities are concentrated incapital region and other some mega cities.
Land use (2010)

CapitalRegion Surface: 377,914 km2
 Population : 126 million (2012)
 GDP: 475.8 Trillion yen (2012)($4.66 Trillion, 1$=102yen)High Density
200km

Low Density

Population density distribution

3

Economy Growthhigh‐economic growthstability

bubbleeconomypost‐
bubbleeconomyGDP per Capita

Heavy Industry & Electricity

GDP per Capita (x 100 USD)

Population ( x million )Population

Population Decrease

Pollution
Environmental Awareness
Energy Efficiency

4Structural Methods of Buildings(1) Residential buildings(a) In case of detached houses, share of wooden houses is around 90 %.
(b) In case of apartments, share of wooden apartments is around 30 %.
(c) It had been prohibited to construct wooden apartments with three or more stories forlong time in Japan. Under the current codes, it is possible to construct them withrequired counter measures against fire.

New Housing Starts (FY 2009: April 2009 – March 2010)
Total： 775,277 units
Detached Houses: 388,407 units

Apartments : 386,870 units
WoodenWooden102,737 (27%)

333,961 (86%)
Non-wooden 284,133 (73%)
RC, S, etc.

Non-wooden 54,446 (14%)
5(2) Buildings other than residentialbuildings(a) Wooden structure was the dominant
type of structure until the end of 19thcentury.
Before the introduction of the brickstructure in the 1860s, and theintroduction of the steel structure andreinforced concrete structure in 1900‐
1920, the wooden structure was thedominant type of structure, including
structure for public use, temples,shrines, and commercial use. Some ofthem still remain in the country.

Todaiji‐temple,wooden building
with height of 46.8 m
1709

Himeji‐castle,wooden building
with height of 31.5 mfrom the topof the stone wall
1608(b) From the end of 19th century, construction methods other than wooden construction
method was promoted for large buildings.
Construction methods other than wooden construction method was promoted for large
buildings, because wooden buildings were considered vulnerable to fires and inferior interms of durability.
6(3) Reevaluation of Wooden Buildings
In the 1980s, Japanese people reevaluated wooden buildings, and new engineering and new
administrative measures made it possible to construct large wooden buildings again.

(4) High‐rise Buildings(a) It was prohibited to construct buildings with height of
more than 31 m for long time (until 1963), because
Japan is earthquake‐prone country.
(b) In 1968, The first super high‐rise building in Japan wasconstructed, of which height was 156 m, owing to theprogress of building technology.
(c) There are around 2,500 super high‐rise buildings withheight of more than 60 m.

Kasumigaseki‐building
Steel structure with height of 156 m
36 floors on the ground, 1968
7Total Floor Areas of Annual Building Starts
in Each Type of Construction in Japan (unit: 1,000 m2)(1) Share of wood structure is stably high in Japan.
(2) Share of masonry is very low in Japan.

300,000
250,000

Total

200,000

Wood
Steel

150,000

RC
100,000

SRC
Others

50,000
013

1951

57

911 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 611961

1971

1981

1991

2001

2011

8Urbanization
Damage of World War II (1945)‐ More than 200 cities in Japan were heavily bombed
in 1944 and 1945.
‐ Around 300,000 people were killed.
‐ 15 million people lost their houses.

9Rapid Urbanization in 1950‐1970s
Population

Current City Planning
Law was enforced.

Milllion people
70

60

50

Rapid urbanization caused‐ sprawl around the fringe oflarge city
‐ disorder configuration of land
use in the city

40

Rapid Urbanization
around large cities

30

20

Urban
area
Large City
Area

10

Rural Area
Rural
area
0
1920

1925

1930

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

Year

10

1960

Urbanization in Tokyo Metropolitan Area
20 years

1980
20 years

2000
Population density(persons / ha)
Population
Density(人口密度)≧200人/ha ≧ 200200＞ Population Density
200 人/ha＞(人口密度)≧100人/ha ≧ 100100 人/ha＞(人口密度)≧ 50 人/ha50＞＞Population
PopulationDensity
Density
人/ha＞(人口密度)≧25人/ha ≧≧5025
1005025人/ha＞(人口密度)≧＞ Population 10Density
25人/ha ≧ 1010人/ha＞(人口密度)≧＞ Population Density
105 人/ha ≧ 5
Population Density
5 5＞人/ha＞(人口密度)

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Sprawl around the fringe Area of city
Agricultural Land and built‐up area
coexist, here and there.

12Earthquake and Tsunami
Japan is located on the boundaries of four Plates.
Around Japan
World Map of Plate Boundary13

(1) Great Kanto Earthquake (1923)
It hit Tokyo and surrounding regions and caused
simultaneous outbreaks of fire in many places,with approximately:‐ 450,000 buildings being destroyed by fire, and‐ some 143,000 persons dead or missing.

Devastated area in Tokyo

It became one of the main concerns in building control to construct buildings that canwithstand earthquakes. The Japanese Building Code has required structural calculation inconsidering seismic force since 1924 (The next year of the Great Kanto Earthquake). This wasa forerunner of such requirement in the world.
Specific structural provisions were also strengthened. Strengthened provisions are, forinstance;‐ Wooden braces for wooden buildings (Before amendment, wooden braces were required
only for wooden buildings of 3 or more stories.)‐ Tie hoops for RC buildings.
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(2) Great Hanshin‐Awaji Earthquake (1995)
It hit Kobe city and surrounding regions, and 104,906 buildings collapsed, and 6,148
buildings were severely damaged, causing 6,433 deaths. It is estimated that 80 % of thedeaths were due to falling buildings or furniture.
Most of the collapsed buildings were those which wereconstructed before 1981. 1981 is the year that the newseismic building regulations were enforced. Therefore,
seismic retrofit of old buildings became an urgent issue inJapan.

15(3) Great East Japan Earthquake (2011)
It hit the Pacific coast of Tohoku of Japan. The seismic damage to buildings was not so muchin considering the scale of the earthquake. Extremely destructive tsunami waves attacked
the coast area of Tohoku of Japan and caused around 20,000 people of death or missing.
Followings became focused issues in the field of buildings.
‐ Restriction of buildings in tsunami hazardous area, and‐ Placement of tsunami evacuation building (buildings to help people vertically evacuatefrom tsunami)
In addition to the building control methods, tsunami detecting system and warning system
was improved.
In case where the flood water depth
was more than 2 m, tsunami‐
induced damage was much severer
than the case where the depth wasless than 2 m.

© NILIM/BRI16Tsunami Evacuation BuildingAs of March 2010, 1,790 tsunami evacuation buildings weredesignated in the whole country, according to the design
guideline for tsunami evacuation buildings, which provide
necessary evacuation height, accommodation capacity,
structural requirements, etc. responding to the particularconditions, such as expected flood water depth and location.
Learning from the lessons of the Great East Japan Earthquake,
Structural Design Method from the Viewpoint of Structural
Safety against Tsunami was compiled.
The structural design method will be utilized for:‐ Designation of tsunami evacuation building, and‐ Structural requirements to the buildings in the tsunami
hazardous areas.

building

Image of tsunami
evacuation building

Tsunami evacuation buildingthat withstood tsunami‐ 200m from the coast‐ Flood water depth was morethan 13m.
17Fire incidents
After large buildings became popular, there were sometimes conflagrations in these buildings.
Therefore, Japanese fire code was revised to strengthen fire safety of such buildings.
(1) Fire code concerning necessary number (2) Fire code concerning automatic sprinklerof stairs, interior finishing materials, etc.
systems, etc. was strengthened in 1980s , inconsidering such fire incidents below.
was strengthened in 1973 , in consideringsuch fire incidents below.
Kawaji Prince hotel(1980), 45 deaths

Sen‐nichi department store(1972), 118 deaths

Taiyo department store(1973), 100 deaths

Hotel New Japan(1982), 33 deaths

18Conflagrations
The traditional Japanese building structure is wooden. Even now, most newly‐built detachedhouses are wooden structures. On the other hand, Japan has a characteristic climate of dry air
in winter, seasonal strong winds, and foehn phenomena that arises in certain areas because of
the mountainous land. Densely‐built wooden buildings and the characteristics of climate
produce a very high threat of fires of both small and large.
Therefore, it has been one of the main concerns in building control to prevent conflagrations
by means of covering roofs and exterior walls with noncombustible materials, especially incentral urban areas. Such restrictions have been in effect in Japan for around 350 years.

Wooden built‐up area inJapan©Wakkanai Fire Department

19Other factors(1) Typhoon and snow
Japan is also situated in the path of typhoons. Buildings face the threat of strong winds fromtyphoons, and buildings near mountains are threatened by landslides caused by heavy
rainfall of typhoons. Therefore, buildings must be able to resist the strong winds fromtyphoons. The possibility of landslides must be considered when planning for construction in
hilly areas. Additionally, in the northern part of Japan, the weight of accumulated snow on
roofs must be considered.

(2) HealthIn order to secure the health of occupants and public health in general (including sick houseissues), buildings must have an adequate sanitary system and so on.

(3) City planning
From the viewpoint of city planning, buildings are required to be designed within a certain
height, to meet land‐use planning, and so on. In many countries, such requirements (zoningcodes) are provided apart from the requirements for building safety.

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Chapter 4

Local Authorities in Japan

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Local Authorities in Japan (as of Jan.2013)
administrative entity

responsible area

National Government

National Government is responsible for whole country of Japan.

47 prefectures
localauthorities

1,742 municipalities

Japanese territory is composed of 47 prefectures.
Japanese territory is composed of 1,742 municipalities. Allmunicipalities belong to any prefecture. Each municipality iscalled a city, town, or village. There are 812 cities, 746 towns,
and 184 villages. They are municipalities.
<Kanagawa Prefecture, for example>

47 Prefecturesin JapanKanagawa prefecture iscomposed of 33 municipalities(19 cities, 13 towns and 1village). They are shown in theleft figure with red, blue andgreen respectively.

All presidents of local governments (Governors andMayors) and all council members of local authorities aredirectory elected by their local residents.
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Governance System in Japan<Japan>Japan Constitution gives:‐ governance powers (Legislative, Administrative, and Judicial) to the National Government,
and‐ limited governance powers to local authorities.
Therefore, Japanese National Government issues Building Standard Law and relating official
documents. Then, local authorities administrate building control on individual building
projects.
<USA, for example>
USA (United States of America) is a federation of states, which is quite different from Japanese
governance system. In case of USA, each state originally had all governance powers, then allstates agreed to transfer part of their governance powers, such as diplomatic right anddefense right, to the federal government through their constitution. Therefore, in USA,governance power relating to building control is still owned by each state and large
municipalities. Federal government does not get involved in building control.

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