The building industry has evolved over thousands of years to develop multiple types of construction. With so many variations, it has become essential for regulatory authorities to establish guidelines that ensure the safety and security of building occupants. In India, the NBC (National Building Code) has specified kinds of construction that ensure this safety and streamline building processes. Keep reading to understand the building construction types as per NBC regulations in India, along with important guidelines for different building types.
Types of Construction As per NBC
The Indian National Building Code (2016): Volume 1 divides construction types on the basis of the following factors:
Construction Classification Based on Fire and Life Safety
Based on the levels of fire safety, the National Building Code of India has classified the types of construction buildings into four different types, each with decreasing levels of fire resistance:
Type 1
This kind of construction represents the highest levels of fire safety standards in India. It involves the use of materials that have a very high fire resistance rating for all structural and non-structural components, including beams, columns, slabs and roofs. Such buildings can typically resist fires for 2-4 hours and provide optimal fire safety.
Type 2
This type of construction projects have a good fire resistance, but lower than the Type 1 projects. Structural components such as beams, columns and slabs here have a fire resistance rating of 2-4 hours, while non-structural elements have a resistance of around 2 hours.
Type 3
Type 3 kinds of construction work have much lower fire resistance. In this type, a combination of both combustible and non-combustible materials is used for construction. This type can be adopted for small and/ or low-rise buildings where occupants can quickly access exits in case of a fire.
Type 4
Construction work types with minimal fire resistance come under this category. Majorly, combustible materials such as timber are used for structural framing, walls and roofs. Such construction can only be adopted in temporary structures or very low-occupancy buildings in low-density areas.
NBC Requirements of Fire Ratings for Different Construction Types
As per NBC regulations, the following fire resistance ratings are required for a building to be classified under the different kinds of construction explained above:
| Fire Resistance Rating (minimum value in minutes) | ||||
| Type 1 | Type 2 | Type 3 | Type 4 | |
| Exterior walls | 60 – 240 | 60 – 120 | 60 – 120 | 60 |
| Interior bearing walls, bearing partitions, columns, beams, girders,trusses (other than roof trusses) and framing: | 180 – 240 | 90 – 120 | 60 – 120 | 60 – 120 |
| Floors | 120 | 90 | 60 | 60 |
| Roofs | 60 – 120 | 60 – 90 | 60 | 60 |
| Fire check doors and lift enclosures | 120 | 120 | 120 | 120 |
For more detailed information, refer to Part 4: Fire and Life Safety of the NBC (2016): Volume I.
Types of Construction Based on Building Occupancy
Residential (Group A)
This group includes any building which provides sleeping accommodation for normal residential purposes. It may or may not include cooking and dining spaces. Residential construction is further sub-categorised as follows:
- Subdivision A-1: Lodging and rooming houses
- Subdivision A-2: 1 – 2 family private dwellings
- Subdivision A-3: Dormitories
- Subdivision A-4: Apartment houses
- Subdivision A-5: Hotels
- Subdivision A-6: Starred hotels
Typical spaces included in residential buildings are bedrooms, living rooms, dining rooms, washrooms and kitchens.
Educational (Group B)
Educational construction includes any buildings that are used for instructing, educating or recreation for more than 20 students. This includes schools, colleges, tuition centres and training academies. This type of buildings is further divided into two types:
- Subdivision B-1: School buildings up to senior secondary level (with a minimum of 20 students)
- Subdivision B-2: All others/ training institutions (with a minimum of 100 students)
Typical Features:
Educational buildings generally have the following features/ spaces:
- Small to large-sized classrooms with desks or working areas
- Office spaces for the teaching staff and administration
- Common spaces and facilities such as washrooms, libraries, labs and playgrounds.
- Assembly spaces such as halls, fields/ grounds and auditoriums.
- Circulatory spaces like corridors, lifts and staircases (generally designed to be slip-resistant and child-friendly)
Institutional (Group C)
This type of construction includes any building which is used for purposes such as medical or other treatment or care of people suffering from physical or mental illness, disease or infirmity, care of infants or aged persons and for penal or correctional detention. Such buildings typically provide sleeping accommodation for the occupants. They are further classified into the following types:
- Subdivision C-1: Hospitals and sanatoriums
- Subdivision C-2: Custodial institutions
- Subdivision C-3: Penal and mental institutions
Typical Features:
Institutional buildings generally have the following features/ spaces:
- Small to large-sized wards/ cells (can be individual or shared) with beds and washroom facilities (may be common washrooms or attached).
- Office spaces for the administration and working staff
- Waiting rooms, lounges and consultation rooms
- Common spaces and facilities such as washrooms and canteens
- Circulatory spaces like corridors, lifts and staircases
Assembly (Group D)
Assembly building structure types include any building where not less than 50 persons congregate or gather for amusement, recreation, social, religious, patriotic, civil, travel or similar purposes. This includes,
- Theatres
- Assembly halls
- Auditoriums
- Exhibition halls
- Museums
- Skating rinks
- Gyms
- Restaurants
- Religious places
- Dance halls
- Club rooms
- Passenger stations
- Air terminals
- Surface and marine public transportation services
- Stadiums
Typical Features:
Assembly buildings may often have the following features/ spaces:
- Small to large-sized gathering spaces (lounges, auditorium seating, dining tables, etc, depending on the type of building)
- Office spaces for the administration and working staff
- Common spaces and facilities such as washrooms, food courts and waiting areas.
- Large circulatory spaces like corridors, lifts and staircases (each with a minimum width of 1.5m to allow large crowds to move simultaneously).
Business (Group E)
Business buildings include any building which is used for transaction of business, for keeping of accounts and records and similar purposes, professional establishments, service facilities, etc. City halls, town halls, courthouses and libraries are part of this type of building construction project if their principal function is the transaction of public business and keeping of books and records.
Typical Features
Business buildings generally have the following features/ spaces:
- Small to large-sized meeting spaces/ rooms for conducting daily activities/ functions.
- Office spaces for the administration and working staff
- Common spaces and facilities such as washrooms and canteens
- Circulatory spaces like corridors, lifts and staircases (with larger widths to accommodate a large number of people)
- Storage rooms/ record-keeping rooms.
Mercantile (Group F)
This category includes any spaces used as shops, stores, markets or for display and sale of merchandise, either wholesale or retail. These kinds of buildings are further subdivided as follows:
- Subdivision F-1: Shops, stores, departmental stores, markets (any with a covered area <500 sq m).
- Subdivision F-2: Shops, stores, departmental stores, markets (any with a covered area >500 sq m).
- Subdivision F-3: Underground shopping centres.
Typical Features:
Mercantile buildings often include the following spaces/ features:
- Mechanical ventilation systems like air conditioners, coolers and heaters.
- Small to large-sized retail spaces (may also include kiosks and pop-up stores)
- Common facilities like washrooms, food courts, gaming centres, movie theaters and restaurants.
- Large circulatory spaces like corridors, lifts, escalators and staircases (each with a minimum width of 1.5m to allow large crowds to move simultaneously).
- Storage and administrative spaces
- Parking facilities.
Industrial (Group G)
These include any building in which products or materials of all kinds and properties are fabricated, assembled, manufactured or processed. It includes assembly plants, industrial laboratories, dry cleaning plants, power plants, generating units, pumping stations, fumigation chambers, laundries, buildings or structures in gas plants, refineries, dairies and saw-mills. Different building types under this category are:
- Subdivision G-1: Buildings used for low hazard industries
- Subdivision G-2: Buildings used for moderate hazard industries
- Subdivision G-3: Buildings used for high hazard industries
Typical Features:
Industrial buildings generally have the following features/ spaces:
- Good natural ventilation as well as extremely effective mechanical ventilation systems to ensure the removal of toxic air.
- Thoroughly detailed emergency evacuation pathways, including fire-escape staircases, corridors and exits.
- Large halls/ spaces used for manufacturing, processing and other such functions.
- Small administrative and office spaces, along with washrooms and storage facilities.
Storage (Group H)
This type of building structures includes any structure that is mainly used for the storage or sheltering of goods, ware or merchandise (excepting those that involve highly flammable or explosive products or materials), vehicles or animals, as well as for servicing, processing or repairs related to storage. It includes:
- Truck and marine terminals
- Garages
- Hangars
- Grain elevators
- Barns and stables
- Cold storage facilities
- Freight depots
- Transit sheds and storehouses.
Typical Features:
The presence of comparatively few people in relation to the total area is a defining feature of storage buildings. They include spaces like:
- Large storage areas with shelves, racks, cupboards and other interior partition features to organise storage elements efficiently.
- Small offices and washroom facilities
- Circulatory spaces like corridors, staircases and lifts (with larger sizes and capacities to facilitate the movement of large and/or heavy goods).
Hazardous (Group I)
Hazardous types of building structures include any building or portion of a building used for the storage, handling, manufacturing or processing of:
- Highly flammable or explosive materials or products that have the potential to burn extremely quickly and/ or to produce toxic fumes or explosions. Example: Fireworks manufacturing units.
- Highly corrosive, toxic or noxious alkalis, acids or other liquids or chemicals that produce flame, fumes, and explosive, poisonous, irritating or corrosive gases. For example, petrol pumps and mines.
- Any material producing explosive dust mixtures that cause matter to split into fine particles that are susceptible to spontaneous ignition. For example, nuclear power plants.
Typical Features:
Hazardous buildings generally have the following features/ spaces:
- Good natural ventilation as well as extremely effective mechanical ventilation systems to ensure the removal of toxic air.
- Thoroughly detailed emergency evacuation pathways, including fire-escape staircases, corridors and exits.
NBC Guidelines for Different Types of Construction
The NBC also provides guidelines for each type of construction work, in which some of the important ones are as follows:
Floor Area Ratios
Floor Area Ratio (FAR) depicts the maximum area that can be built on a plot of land. The allowed FAR for different construction types are:
| Floor Area Ratios for Buildings Facing One StreetThat is Atleast 9m Wide | ||||
| Type 1 | Type 2 | Type 3 | Type 4 | |
| Residential | UL | 2 | 1.4 | 1 |
| Educational | UL | 2 | 1.4 | 1 |
| Institutional | UL | 1.5 | 1 | 0.8 |
| Assembly | UL | 1 | 0.7 | 0.5 |
| Business | UL | 2.9 | 2.3 | 1.6 |
| Mercantile | 8 | 1.8 | 1.4 | 1 |
| Industrial | 7.5 | 1.9 | 1.6 | 1.3 |
| Storage | 6 | 1.5 | 1.3 | 1 |
| Hazardous | 2.8 | 1.1 | 0.9 | NP |
Here, UL stands for ‘unlimited’, while NP stands for ‘Not Permitted’.
However, the permissible FAR in different cities, areas and locations are also dependent on several other factors like municipal regulations and land use classifications.
Access Pathways
For fire safety in buildings, NBC has defined the minimum width of stairways, ramps and other level surfaces (such as corridors and walkways) to be designed for different construction types based on the number of people expected to use the building:
| Staircase Width per Person (mm) | Width of Ramps and Level Components per Person (mm) | |
| Residential | 10 | 6.5 |
| Educational | 10 | 6.5 |
| Institutional | 15 | 13 |
| Assembly | 10 | 6.5 |
| Business | 10 | 6.5 |
| Mercantile | 10 | 6.5 |
| Industrial | 10 | 6.5 |
| Storage | 10 | 6.5 |
| Hazardous | 18 | 10 |
Exit Distances
To ensure safe exits in case of fires and other hazards, the maximum travel distance across a floor to reach an exit is as follows:
| Maximum Travel Distance to an Exit in a Floor (m) | ||
| Types 1 and 2 | Types 3 and 4 | |
| Residential | 30 | 22.5 |
| Educational | 30 | 22.5 |
| Institutional | 30 | 22.5 |
| Assembly | 30 | 30 |
| Business | 30 | 30 |
| Mercantile | 30 | 30 |
| Industrial | 22.5 – 45 (based on subdivision) | Not Permitted |
| Storage | 30 | Not Permitted |
| Hazardous | 22.5 | Not Permitted |
Ensuring the Best Services for All Building Construction Types
In any kind of construction project, fire and life safety, along with structural stability of the building, are of utmost importance. Brick & Bolt, a tech-enabled construction company, conducts 470+ quality checks (QASCON) in all its projects, ensuring that premium quality is maintained throughout. The company provides end-to-end construction services with the aid of architects and contractors who are well-versed with national and international building codes, ensuring compliance with every safety regulation. Top-quality building materials supply is also assured, streamlining construction processes greatly. To get the best building services for all types of construction projects, contact Brick & Bolt today!
Apoorva H P Achar