What Is BNBC 2020?
The Bangladesh National Building Code (BNBC) 2020 is the comprehensive building regulation for Bangladesh, covering structural design, fire protection, electrical systems, plumbing, mechanical systems, accessibility, and construction practices. It replaced BNBC 1993 and represents a major update aligned with current international standards.
BNBC 2020 is not a standalone invention — it heavily references and adapts international codes and standards, primarily from the US (IBC, ACI, ASCE, NFPA, ASHRAE) with adaptations for Bangladesh-specific conditions including seismic zones, wind speeds, soil conditions, and climate.
BNBC 2020 Structure
| Part | Title | Key Content | Primary International Reference |
|---|
| Part 1 | Scope and Administration | Application, definitions, enforcement, permits | IBC Chapter 1 |
| Part 2 | General Building Requirements | Site planning, means of egress, accessibility, interior environment | IBC Chapters 10-12 |
| Part 3 | Classification of Buildings | Occupancy classifications, building height/area limits, construction types | IBC Chapters 3-5 |
| Part 4 | Fire Protection | Fire resistance, detection, suppression, means of egress, fire fighting access | NFPA 13, 72, 101 |
| Part 5 | Building Materials | Material specifications, testing, quality control | ASTM, ACI standards |
| Part 6 | Structural Design | Loads (dead, live, wind, seismic), concrete, steel, masonry, timber, foundations | ASCE 7, ACI 318, AISC 360 |
| Part 7 | Construction Practices | Site safety, formwork, concrete placement, quality assurance | ACI 301, 347 |
| Part 8 | Electrical and Communication | Power distribution, wiring, lighting, communication, lightning protection | IEC 60364, NEC (NFPA 70) |
| Part 9 | Plumbing and Drainage | Water supply, sanitary drainage, storm drainage, fixtures | IPC, UPC |
| Part 10 | Mechanical Systems | HVAC, ventilation, energy conservation | ASHRAE 62.1, 90.1, 55 |
Key Changes from BNBC 1993 to 2020
| Area | BNBC 1993 | BNBC 2020 | Significance |
|---|
| Seismic zones | 3 zones (Z=0.075-0.25) | 4 zones (Z=0.12-0.36) | Higher seismic forces for most of Bangladesh |
| Wind speeds | Basic wind speed map (lower values) | Updated wind speed map (195-260 km/h) | Higher wind loads, especially coastal |
| Concrete code | Based on ACI 318-95 | Based on ACI 318-14/19 | Modern ductility requirements, performance-based |
| Fire protection | Basic requirements | Comprehensive — references NFPA | Detailed sprinkler, alarm, egress requirements |
| Energy | Minimal | Energy conservation chapter (ASHRAE 90.1 based) | First mandatory energy provisions |
| Accessibility | Minimal | Dedicated accessibility requirements | First comprehensive accessibility provisions |
| Soil/foundation | Basic | Detailed geotechnical requirements | Liquefaction assessment required in seismic zones |
Occupancy Classifications
| Group | Description | Examples | IBC Equivalent |
|---|
| A | Assembly | Theatres, mosques, stadiums, restaurants >50 occupants | A-1 through A-5 |
| B | Business | Offices, banks, professional services | B |
| E | Educational | Schools, universities, training centres | E |
| F | Factory/Industrial | Manufacturing, assembly, processing | F-1, F-2 |
| H | Hazardous | Chemical storage, explosive manufacturing | H-1 through H-5 |
| I | Institutional | Hospitals, prisons, care facilities | I-1 through I-4 |
| M | Mercantile | Retail shops, markets, malls | M |
| R | Residential | Houses, apartments, hotels, dormitories | R-1 through R-4 |
| S | Storage | Warehouses, parking garages | S-1, S-2 |
| U | Utility | Agricultural buildings, fences, tanks | U |
Seismic Zones
| Zone | Z Factor | Areas | Design Implication |
|---|
| Zone 1 | 0.12 | Southwest Bangladesh (Khulna, Barisal, parts of Rajshahi) | Lowest seismic demand — but still requires seismic design |
| Zone 2 | 0.20 | Central Bangladesh including Dhaka, Comilla, Faridpur | Moderate seismic demand — most commercial buildings are here |
| Zone 3 | 0.28 | North-central Bangladesh (Mymensingh, Tangail, northern Dhaka) | Significant seismic demand — near Madhupur fault |
| Zone 4 | 0.36 | Northeast Bangladesh (Sylhet, Rangpur, Dinajpur) | Highest seismic demand — near Dauki fault |
Critical note: BNBC 1993 used Z=0.15 for Dhaka. BNBC 2020 uses Z=0.20 — a 33% increase in design seismic force. Buildings designed to the 1993 code may have insufficient seismic capacity by current standards.
Wind Speed Map
| Region | Basic Wind Speed (km/h) | Context |
|---|
| Dhaka | 195 | Inland — lowest wind zone |
| Chittagong | 225-245 | Coastal — cyclone exposure |
| Cox's Bazar | 245-260 | High cyclone risk zone |
| Sylhet | 195-210 | Inland — moderate |
| Coastal islands | 260 | Maximum — direct cyclone path |
Enforcement Reality
- Design vs construction gap: BNBC 2020 is technically rigorous, but enforcement depends on RAJUK/CDA capacity and willingness. Many buildings are constructed without full code compliance.
- Pre-2020 buildings: Buildings designed before BNBC 2020 (and many before BNBC 1993) may not meet current seismic, wind, or fire requirements. There is no mandatory retrofit requirement.
- Structural: Best enforced — RAJUK reviews structural drawings. But post-construction modifications and extra floors undermine the design.
- Fire: BNBC 2020 fire provisions are comprehensive but widely non-compliant. Many buildings lack basic fire detection.
- Electrical: BNBC 2020 references IEC 60364 but electrical installation quality varies enormously.
- Energy: Energy provisions are new in BNBC 2020 — enforcement is minimal.
- Accessibility: Provisions exist but implementation is rare beyond basic ramps.
References
- BNBC 2020 — Bangladesh National Building Code (Housing and Building Research Institute)
- ICC — International Building Code (IBC)
- ACI 318 — Structural Concrete
- ASCE 7 — Minimum Design Loads
- NFPA — Fire Protection Standards
- ASHRAE — HVAC and Energy Standards
- IEC 60364 — Low-Voltage Electrical Installations
