country-japan

Research

Japan architectural code and regulatory reference. Covers the Building Standards Act (Kenchiku Kijun Ho, 1950, fundamentally revised 1998 toward performance-based regulation and 2007 strengthening post-Aneha incident), Building Standards Law Enforcement Order (Kenchiku Kijun Ho Shiko Rei) and MLIT Notifications (Kokuji); the parallel Fire Service Act and Fire Service Law Enforcement Order administered by Fire Department (Shobosho); Energy Conservation Act 1979 superseded by Act on the Improvement of Energy Consumption Performance of Buildings (Kenchikubutsu Sho-Energy Ho) 2015 + amendment 2022; Heart Building Law 2006 (Barrier-Free Law) and JIS S 0026 accessibility standards; City Planning Act with 12 use districts and ratio-based regulation (Yoseki-ritsu volumetric, Kenpei-ritsu coverage, daylighting + setback ratios); the unique two-level seismic design philosophy (Level 1 475-year + Level 2 2475-year), 1981 New Seismic Standard (Shintaishin), Energy Absorption Member design + base isolation + damper systems; AIJ Recommendations for Loads on Buildings 2015; CASBEE (Comprehensive Assessment System for Built Environment Efficiency); BCJ (Building Center of Japan) structural performance evaluation; Architect Law and Class 1/2/ Mokuzo (timber) architect designations; Land + Building Lease Act; and the prefecture + Designated City (Seirei Shitei Toshi) + Core City (Chukaku Shi) administrative tiers.

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Country: Japan

Architectural code and regulatory reference for projects in Japan (all 47 prefectures + Tokyo Metropolis). Activate this skill on any Japanese city/prefecture reference, JPY currency, mention of "Kenchiku Kijun Ho"/"BSL"/"Sho-Energy Ho"/"CASBEE"/"AIJ"/"BCJ"/"Shintaishin", or Japanese architectural terminology (yoseki-ritsu, kenpei-ritsu, kakunin-shinsei, kanseikensa, joryoku-do, koshou-tatemono, mokuzo).

1. Regulatory Hierarchy

Japan operates as Archetype D (Centralised National + Strong-Form Clauses). Building regulation is national, administered through prefectures + designated cities under Building Standards Act delegated authority. Some matters are devolved to designated cities.

1.1 Authority Stack

LEVEL 1 -- NATIONAL
  Ministry of Land, Infrastructure, Transport and Tourism (MLIT, Kokudo Kotsu Sho)
    Housing Bureau (Jutaku Kyoku) -- residential policy
    City Bureau (Toshi Kyoku) -- urban planning
    Land and Real Estate Industry Bureau
    + issues MLIT Notifications (Kokuji) -- detailed technical requirements
  Ministry of Internal Affairs and Communications (Somu Sho) -- Fire Service Agency
  Ministry of Health, Labour and Welfare (Kosei Rodo Sho) -- hospital regulations
  Ministry of Economy, Trade and Industry (METI, Keizai Sangyo Sho) -- energy + product safety
  Ministry of the Environment (Kankyo Sho) -- environmental
  Ministry of Education (MEXT) -- school facilities
  National Police Agency -- some safety regulations

LEVEL 2 -- PREFECTURE (todofuken) + DESIGNATED CITIES
  47 prefectures + 20 Designated Cities (Seirei Shitei Toshi) -- e.g.,
    Tokyo (special category as Metropolis), Osaka, Yokohama, Nagoya, Sapporo, Kobe,
    Kyoto, Fukuoka, Hiroshima, Sendai, Kawasaki, Saitama, Chiba, Niigata, Hamamatsu,
    Sakai, Shizuoka, Okayama, Sagamihara, Kumamoto
  Tokutei Gyousei Cho (Designated Administrative Officer) -- typically prefectural or
    designated-city housing department; oversees Kakunin-shinsei (building confirmation)
  Building Examiners (Kenchiku Shujikan) -- public officials
  Designated Confirmation Inspection Agencies (Shitei Kakunin Kensa Kikan) -- private
    since 1998 reform; competitive choice

LEVEL 3 -- MUNICIPALITY (shi-cho-son)
  Smaller cities, towns, villages -- if not Designated City, defer to prefecture for building
    confirmation but handle planning under City Planning Act
  Local Fire Departments (Shobosho)

LEVEL 4 -- PROJECT
  Kakunin-shinsei (Building Confirmation Application) submitted by Class 1 Architect or
    qualified delegate
  Structural calculations checked: (a) self-check up to threshold (BCJ-evaluated etc.),
    (b) Performance Evaluation by accredited body (BCJ, Japan Engineering Standards
    Foundation, etc.) for taller/special buildings
  Periodic inspection during construction (Kanseikensa)
  Article 7 Inspection (kansei kensa) -- final inspection before occupancy

1.2 Building Standards Act Structure

The Building Standards Act 1950 (BSA) was fundamentally reformed in 1998 (introducing performance-based regulation) and amended again in 2007 (post-Aneha falsified structural calculations scandal, which strengthened independent structural review).

Structure:

BSA itself (Kenchiku Kijun Ho) -- legislative framework
BSL Enforcement Order (Kenchiku Kijun Ho Shiko Rei) -- Cabinet Order with detailed implementing regulations
BSL Enforcement Regulations (Kenchiku Kijun Ho Shiko Kisoku) -- Ministerial Order on procedure
MLIT Notifications (Kokuji) -- detailed technical specifications (hundreds)
JIS Standards (Japanese Industrial Standards) -- material + product specifications

1.3 Tokyo Special Status

Tokyo Metropolitan Government (Tokyo-to) has 23 special wards (Tokubetsu-ku) functioning as municipalities + the multi-city Tama region. Building confirmation in Tokyo's 23 wards is generally handled by the Tokyo Metropolitan Government Bureau of Urban Development + ward offices for smaller works. Tokyo has its own Tokyo Metropolitan Ordinance on Building Standards -- supplements BSA.

2. Building Standards Act Core Requirements

2.1 Building Classification (Yoto Bunkenchiku)

BSA classifies buildings by use + structure + scale:

Use Category	Description
Tokushu Kenchikubutsu	Special Buildings -- assembly, hospital, school, hotel, etc.; many require BCJ structural eval, additional fire requirements
Ippan Kenchikubutsu	General Buildings -- offices, factories

Special structures (high-rise, large span, special concrete) require BCJ structural performance evaluation per BSA Article 20 + sub-clauses.

2.2 Yoseki-ritsu + Kenpei-ritsu (Volume Ratio + Coverage)

The two principal Japanese density controls:

Yoseki-ritsu (容積率, FAR) -- total above-grade GFA / lot area; values 50-1300% by use district
Kenpei-ritsu (建蔽率, BCR/Building Coverage Ratio) -- footprint / lot area; values 30-80% by use district

2.3 Use Districts (City Planning Act -- 13 categories)

Use District	Yoseki-ritsu Range	Kenpei-ritsu Range	Use
First Class Low-rise Residential (Daiichi-shu Tei-so Jukyo)	50-200%	30-60%	Houses ≤10/12 m height
Second Class Low-rise Residential	50-200%	30-60%	Similar +small shop
First Class Mid/High-rise Residential	100-500%	30-60%	Apartments + small commerce
Second Class Mid/High-rise Residential	100-500%	30-60%	+ medium retail
First Class Residential	100-500%	50-80%	Residential + offices/retail moderate
Second Class Residential	100-500%	50-80%	+ entertainment limited
Quasi-Residential	100-500%	50-80%	Roads + residential mix
Neighbourhood Commercial	200-500%	60-80%	Shops + service
Commercial	200-1300%	80%	Full commerce + tall buildings
Quasi-Industrial	100-500%	50-80%	Light industrial
Industrial	100-400%	50-60%	Factory mix
Exclusively Industrial	100-400%	30-60%	Heavy industry only
Field of Tanada	(rural special)	--	Agricultural

2.4 Sun-Right + Sky-Right + Daylighting (Hisho-mado Jisshin)

A particularly Japanese set of regulations:

Daylighting setback (Nichi-sho ki-zen) -- buildings must allow specified hours of sun (3-5 hours mid-winter) to reach adjacent properties; codified per area; varies by use district
Sky exposure plane / road-set-back-ratio plane (Doro Shasen Seigen) -- imaginary inclined plane from far edge of road; building cannot project beyond
Adjacent-property setback plane (Rinchi Shasen Seigen) -- imaginary plane from neighbor's lot line
Northern exposure setback (Hokugawa Shasen) -- protects northern neighbours from overshadowing
Absolute height limit in low-rise residential -- 10 m or 12 m

These controls collectively shape Japanese urban form -- often producing characteristic "stepped" or "wedding cake" massing.

2.5 Structural Articles 20 + Bekkihyo (Annexes)

BSA Article 20 sets four tiers of structural review:

Tier 4 (lightest) -- low buildings; sample-rule check
Tier 3 -- moderate; specific structural calculation
Tier 2 -- high-rise or special; advanced calc + BCJ-evaluated
Tier 1 (heaviest) -- super-high-rise or special structural performance; BCJ Performance Evaluation + MLIT Minister Approval required

Tier 1 cases: building > 60 m, or special types (seismic isolation building, special structural performance like FRPs, ultra-light long-span etc.)

2.6 Travel Distance + Egress (BSA + Enforcement Order Article 120-122)

Parameter	Sprinklered	Unsprinklered
Max travel distance (general)	50 m	30 m
Max travel distance (assembly, dormitory)	40 m	30 m
Max travel distance (hospital, ROS-protected)	50 m	30 m
Min corridor width (Special Buildings >= 200 m2/floor)	1.6 m double-loaded; 1.2 m single	--
Min corridor width (residential each floor)	1.2 m double-loaded; 0.9 m single	--
Min stair width (Special Buildings >= 200 m2/floor)	1.4 m	1.4 m
Min stair width (residential >= 600 m2 total)	1.2 m	1.2 m
Min door clear width	800 mm (Special Buildings); 750 mm (general)	--

2.7 Two Means of Escape

Two means of escape required when:

Special Buildings any storey > 100 m2
Mid-rise Residential > 5 storeys (or > 500 m2 floor)
High-rise > certain thresholds

3. Seismic Design

3.1 Two-Level Seismic Design

The defining feature of Japanese structural design. Building must be safe under:

Level 1 (Damage Limit) -- frequent earthquakes (~50-year return) -- building remains undamaged, structurally elastic. Design seismic shear coefficient C0 = 0.2 (multiplier on weight).
Level 2 (Life Safety / Ultimate) -- rare earthquakes (~475-year return, possibly 2475-year for important structures) -- building may sustain damage but no collapse. Design shear coefficient C0 = 1.0.

The 1981 revision (Shintaishin -- "New Earthquake-Resistance Standard") introduced this two-level approach. Buildings built before 1981 are designated "Kyu-taishin" and many have been retrofitted.

3.2 Building Classifications

General buildings: design per Level 1 + Level 2 capacity
Important buildings (hospitals, communications, government, large assembly): design factor higher (~1.5×)
Hi-rise buildings (> 60 m): site-specific seismic motion + dynamic analysis + BCJ performance evaluation
Base-isolated (Menshin) buildings: separate design route + BCJ evaluation
Damper (Seishin) buildings: separate design route

3.3 Site Classification + Seismic Coefficients

Japan ground classes (BSA Enforcement Order Article 88):

Class 1 (Type 1 ground -- rocky, strong) -- C0 multiplier baseline
Class 2 -- alluvial, moderate
Class 3 -- soft (e.g., Tokyo Bay landfill) -- highest C0 multiplier

3.4 Standards + References

Building Standards Act + Enforcement Order Articles 81-87 + 88
AIJ Recommendations for Loads on Buildings 2015 -- Architectural Institute of Japan
AIJ Design Standards for Reinforced Concrete Structures (RC), Steel Structures (S), Composite (SRC)
JSCE standards -- mainly bridges/civil
BCJ Performance Evaluation -- for taller buildings

4. Fire Safety (Fire Service Act + BSA)

4.1 Two Statute System

Japan uniquely operates fire safety under two statutes:

Building Standards Act -- "preventive fire-resistance" (Yobo Bosai) -- structural compartmentation, fire-resistance, smoke control DESIGN
Fire Service Act (Shobo Ho) -- "active fire fighting" (Soshou Bosai) -- sprinkler, detection, hose reel, evacuation equipment, fire-fighting

Plans must be approved by both Designated Administrative Officer (BSA) and Fire Department (FSA).

4.2 BSA Fire Provisions

Fire-resistant building (Taika Kenchikubutsu) -- non-combustible structure, fire-resistance rating per height + use
Semi-fire-resistant (Junitaika) -- intermediate
Combustible (Mokuzo + similar) -- limited heights + areas, primarily low-rise residential

Fire-resistance hours:

Major structural members up to 4 storeys: 1 hour
5-14 storeys: 2 hours
15+ storeys: 3 hours

4.3 Fire Service Act Provisions

Sprinklers required: high-rise above 11 storeys, large floors (>700 m2 special), large theatre, hospital >5 storey etc.
Automatic fire alarms -- per occupancy type + size
Indoor fire hose + Hose reel -- per area
Smoke-removal equipment -- per Article 126 BSA Enforcement Order
Emergency power -- 30 minutes minimum, sometimes 60

4.4 Stair Smoke Protection

Japan emphasizes outside-air stair (To-no-zen Kaidan) -- stairs vented to outside, often via open balcony. Provides smoke-free escape route without requiring positive pressurization.

For tower buildings without external stair access, smoke-resistance compartments (To-no-zen Shitsu) are provided -- lobby + stair both pressurized or vented.

4.5 Post-Disaster Function -- Important Buildings

Hospitals, fire stations, government emergency operations centres, designated evacuation centres designed for post-event functionality -- structural drift limits tighter, redundancies for utilities, separate emergency power.

5. Energy Code (Sho-Energy Ho)

5.1 Act on the Improvement of Energy Consumption Performance of Buildings (Kenchikubutsu Sho-Energy Ho) 2015

Replaced the older Energy Conservation Act 1979 for buildings. Mandatory compliance for:

2017: large non-residential >= 2000 m2
2021: medium non-residential 300-2000 m2
2025 (amendment 2022 effective): ALL new buildings including small residential

Compliance demonstrated via:

Standard route (BEI -- Building Energy Index) -- design primary energy / standard primary energy ≤ 1.0
Simplified route for small buildings (≤300 m2) by Web Pro tool
Performance route -- prescriptive UA + ηA values for envelope, similar to U-value + SHGC compliance

5.2 Climate Zones (Notification No. 265 of 2015 + revisions)

Japan defines 8 climate zones (Region 1 through Region 8) based primarily on HDD (heating degree days):

Zone	Approximate Region	Typical Cities
Region 1	Sub-arctic	Hokkaido east + interior (Asahikawa, Kushiro)
Region 2	Cold	Hokkaido west + Tohoku interior (Sapporo, Aomori interior)
Region 3	Cool-cold	Tohoku coast + Hokuriku (Sendai, Akita, Niigata)
Region 4	Cool	Inland Honshu (Nagano interior, Saitama interior)
Region 5	Temperate	Tokyo, Yokohama, Osaka -- main urban regions
Region 6	Mild	Western Honshu, Shikoku (Hiroshima, Takamatsu, Fukuoka)
Region 7	Warm	Southern Kyushu (Kagoshima)
Region 8	Subtropical	Okinawa

5.3 Envelope Targets (Sho-Energy Ho Performance Route)

Zone	UA (W/m2K) max	ηA (avg solar) max
1	0.40	--
2	0.40	--
3	0.50	--
4	0.60	--
5	0.87	3.0
6	0.87	2.8
7	0.87	2.7
8	--	6.7 (cooling-dominated)

(UA = average U-value over external envelope; ηA = average solar acquisition factor)

5.4 ZEH and ZEB Programs

ZEH (Net Zero Energy House) -- residential; tiered ZEH, ZEH Plus, ZEH+R (resilience-enhanced)
ZEB (Net Zero Energy Building) -- non-residential; tiered ZEB, Nearly ZEB, ZEB Ready, ZEB Oriented

METI subsidies tied to these tiers.

5.5 CASBEE -- Comprehensive Assessment System for Built Environment Efficiency

Japan's own green building assessment system, comparable to LEED + DGNB. Rates by:

BEE (Built Environment Efficiency) = Q (Quality) / L (Load) ratio
Categories: S, A, B+, B-, C
Multiple sub-tools: CASBEE for Buildings (New, Existing, Renovation), Urban Development, Cities

Many municipalities require CASBEE B+ or A as minimum for medium-large buildings.

6. Accessibility (Heart Building Law 2006)

6.1 Heart Building Law (Hito ni Yasashii Machizukuri / Barrier-Free Law)

Act on Promotion of Smooth Transportation of Elderly, Disabled Persons (2006) -- consolidated previous Heart Building Law + Traffic Barrier-Free Law.

Mandatory provisions for:

Designated Buildings: shops > 2000 m2, hospitals, hotels (> 50 rooms), restaurants > 200 m2, theatres + schools above certain size, public buildings
Specific Designated Buildings: subset with stricter standards

6.2 Key Dimensions (Heart Building Law + JIS S 0026)

Element	Dimension
Accessible route	1.2 m (1.5 m preferred); passing space 1.4 x 1.4 m every 50 m
Door clear width	800 mm
Ramp gradient	1:12 max; landings every 6 m run + at top/bottom
Lift cabin	1100 x 1350 mm (Type 1); 1400 x 1600 mm (Type 2 hospital)
Accessible WC	2.0 x 2.0 m; with multi-function: 2.2 x 2.2 m
Accessible parking	3.5 m + access; covered preferred
Tactile flooring	Per JIS T 9251; at platform edges, ramps, stair tops, level changes

6.3 Provision Counts

Accessible parking: 1 per 50 stalls (designated buildings)
Multi-Function Toilet (Tashinooyo Toiret): at least 1 per floor in designated buildings -- combines accessible WC + diaper change + ostomy + emergency call
Hotel accessible rooms: 1 per 50 rooms (designated)
Tactile guidance: comprehensive in transit + public buildings

6.4 Universal Design Beyond Compliance

Japan's robust UD culture extends beyond legal minimum:

Many municipalities have Universal Design Mark / Tsugou (Convenience) certifications
"ChojuJuutaku" (Long-Life Quality Housing) certification for housing
"Tokutei Hyouka" Designated Evaluation for housing accessibility

7. Structural Materials and Standards

7.1 Material Codes

Material	Reference
Reinforced Concrete	AIJ-RC / JASS 5
Steel Structures	AIJ-S / JASS 6
Composite (Steel-Reinforced Concrete -- SRC)	AIJ-SRC
Wood / Timber	AIJ-W / JASS 11 / JAS lumber + glulam standards
Masonry	AIJ-M / JIS A 5406 (block)
Foundations	AIJ-F / BSA Articles + JIS A 5525 (piles)

7.2 JIS Standards

The Japanese Industrial Standards (JIS) provide product-level specifications:

JIS A series -- civil + building
JIS B -- machinery
JIS C -- electrical
JIS G -- iron + steel

7.3 Wind (AIJ Recommendations 2015)

Japan uses basic wind velocity (Vref) at 30 m height -- varies city by city per AIJ map. Tokyo Vref = 34 m/s. Okinawa coastal (typhoon-prone) Vref up to 46 m/s.

Wind-resistant design also separate consideration:

Wind-cycle fatigue for tall buildings
Aerodynamic shape coefficients per wind tunnel testing for >60 m
Cyclonic/typhoon design distinct from synoptic wind, especially in Okinawa + Kyushu

8. Permit Workflow

8.1 Standard Workflow (Kakunin-shinsei)

Pre-application consultation (Jizen Sodan) with prefecture/Designated City Building Department
Preliminary calculations by Class 1 Architect (Ichi-kyu Kenchikushi)
Submit Building Confirmation Application (Kakunin-shinsei) to designated administrative officer OR private confirmation inspection agency
Confirmation Certificate issued (Kakunin Tsuuchi-sho) within statutory period (varies; 7-35 days)
Structural Calculation Conformance Judgment (Kouzou Keisan Tekigosei Hantei) -- if Tier 2/3 structural -- by accredited body
Performance Evaluation by BCJ (or other accredited) -- if Tier 1 structural
MLIT Minister Approval -- if super-high-rise OR special structure
Periodic Inspections during construction (Chuukan Kensa)
Article 7 Inspection (Kanseikensa) -- final
Inspection Certificate (Kanseikensa-Shomeisho) -- equivalent to certificate of occupancy

8.2 Architect Licensing

Class 1 Architect (Ichi-kyu Kenchikushi) -- can design any building scale
Class 2 Architect (Ni-kyu Kenchikushi) -- limited to certain scales/structures
Mokuzo Kenchikushi (Wood-Structure Architect) -- limited to wooden buildings
Examinations administered by MLIT-designated body; renewed periodically with CPD

8.3 Special Buildings -- Building Center of Japan (BCJ) Role

BCJ evaluates buildings beyond standard limits:

Super-high-rise (>60 m) -- structural performance evaluation
Base-isolated (Menshin)
Special structural systems (cable-stayed, tensile, etc.)
Long-span structures
Special materials (CLT large-scale, etc.)

BCJ issues evaluation certificate which the Confirmation Inspection Agency relies on.

9. Climate Design Parameters

9.1 Tokyo (Region 5)

Parameter	Value
Cooling design DB (0.4%)	32-34 deg C
Cooling design WB	26-27 deg C
Heating design DB (99.6%)	0 to -2 deg C
Annual CDD (base 18C)	1100-1300
Annual HDD (base 18C)	2000-2200
Annual GHI	1400 kWh/m2
Wind 3-sec gust (typhoon)	50-55 m/s 0.4% probability
Snowfall	< 100 mm typical / yr

9.2 Sapporo (Region 2)

Parameter	Value
Heating design DB	-8 to -10 deg C
Annual HDD	3500+
Snow ground load	1.5-3.5 kN/m2 (depends on neighbourhood)

9.3 Okinawa (Region 8)

Parameter	Value
Cooling design DB	32-33 deg C
Cooling design WB	28 deg C
Annual CDD	5000+
Annual HDD	~50
Typhoon wind	extreme; design 60+ m/s 3-sec gust
Salt-laden corrosion	severe

10. Quick Numeric Reference

Parameter	Value	Source
Floor-to-floor residential	2.8-3.0 m	BSA + practice
Floor-to-floor office	3.5-4.0 m	Class A spec; 2.5 m min clear
Hotel ceiling clear	2.4 m min	BSA
Corridor width residential (multi-storey)	1.2 m	BSA Enforcement Order 119
Corridor width Special Building	1.6 m	BSA Enforcement Order 119
Stair width residential	1.2 m	BSA Enforcement Order 23
Stair max riser	23 cm (residential); 18 cm (Special)	BSA
Stair min going	15 cm (residential); 24 cm (Special)	BSA
Travel distance sprinklered (general)	50 m	BSA Enforcement Order 120
Seismic C0 (Level 1)	0.2	BSA + AIJ-S
Seismic C0 (Level 2)	1.0 (general); 1.5 (important)	BSA + AIJ-S
UA Tokyo (Region 5)	0.87 W/m2K max	Sho-Energy Ho
Yoseki-ritsu Commercial	200-1300%	City Planning Act
Kenpei-ritsu Residential	30-60%	City Planning Act
Daylight hours required (Region 5 winter)	3 hours mid-winter	Local ordinance

11. Application Workflow

Identify prefecture / Designated City (or special wards in Tokyo).
Identify use district + yoseki-ritsu + kenpei-ritsu + height limit + daylighting setbacks.
Determine if Special Building (Tokushu Kenchikubutsu).
Determine structural review tier (1, 2, 3, 4) per BSA Article 20.
Apply BSA + Enforcement Order + MLIT Notifications for general design.
Apply Fire Service Act + Local Fire Department for fire-fighting systems.
Apply Sho-Energy Ho for energy.
Apply Heart Building Law if Designated Building scale.
Apply AIJ-RC / AIJ-S / AIJ-W standards for structural materials.
Engage BCJ or other accredited body if structural performance evaluation needed.
Cite clauses: "Building Standards Act Article 20", "BSA Enforcement Order Article 120", "MLIT Notification 1457 of 2000 (Kokuji)", "AIJ Recommendations for Loads on Buildings 2015", "Sho-Energy Ho 2015 Article 11", "Heart Building Law Implementation Standards Section 13".

12. Authoritative Sources

MLIT (Ministry of Land, Infrastructure, Transport and Tourism) -- mlit.go.jp
Building Center of Japan (BCJ, Nihon Kenchiku Center) -- bcj.or.jp -- structural evaluation, technical guidelines
Japan Architectural Institute (AIJ, Nihon Kenchiku Gakkai) -- aij.or.jp -- structural recommendations
Architectural Institute of Japan -- JASS series -- Japanese Architectural Standard Specifications
JIS via Japan Standards Association (JSA) -- jsa.or.jp
Fire and Disaster Management Agency (FDMA, Shobo Cho) -- fdma.go.jp
Japan Society of Civil Engineers (JSCE) -- jsce.or.jp
Institute for Building Environment + Energy Conservation (IBEC) -- ibec.or.jp -- CASBEE
METI (Ministry of Economy, Trade and Industry) -- meti.go.jp -- ZEB/ZEH subsidies
Japan Sustainable Building Database (CASBEE certified projects) -- ibec.or.jp/CASBEE
Tokyo Metropolitan Government Bureau of Urban Development -- toshiseibi.metro.tokyo.lg.jp
Each prefecture building department -- prefectural government websites
Architect license examination via Japan Architects Association -- jia.or.jp

Cross-references: load building-codes for general code structure (Japan BSA is distinct -- two-statute fire system); fire-life-safety for general principles overlaid by BSA fire-resistance + Fire Service Act active provisions; accessibility-design for global frameworks then Heart Building Law; building-sustainability for CASBEE + LEED + Passivhaus comparison; structural-systems for seismic-specific design (Japan two-level + base isolation expertise); building-envelope for severe climate (subarctic to subtropical) + typhoon detailing.