Decoding building safety codes: A comparative guide to global building standards

By Avinash Gupta, P.Eng., CBCO, CRBO, LBO, Mohamed S. Mohamed, P.E., P.Eng., and Dominic Esposito, P.Eng.

The most important activity in case of a fire emergency in a building is evacuating occupants to a safe place inside or outside the building before the environment becomes untenable. For the occupants to travel to a safe place (e.g. refuge area) within a building or reach an exterior discharge (street or alley), every occupiable space must have an adequate number of exits and obstruction-free means of egress.

There is a National Building Code of Canada (NBC) proposal to consider including a single exit for residential occupancies. This article summarizes different provisions in other countries that permit a single exit to be provided.

The principal objective of providing more than one independent and remote exit is to ensure that if one exit is blocked by smoke or fire, other exits are available to occupants to evacuate a building safely. Remoteness is not a defined term; nonetheless, exits located at each end of long corridors or sides of a floor areas will satisfy the requirement of a remotely located exit. However, except for small buildings covered under Part 9 of the NBC, the distance between exits is required to be not less than one-half of the floor area’s maximum diagonal dimension but no less than 9 m (30 ft) where a public corridor is provided.

Two examples of fire fatalities in buildings associated with insufficient provision of available exits are the following:

Boston’s Cocoanut Grove nightclub fire was one of the deadliest fires in the United States in 1942. In just 15 minutes, 492 people were killed in the most devastating nightclub fire in history. The reason? A revolving door at the front of the club was more or less the only available means of exit, and the mass exodus quickly jammed it; smoke and flames rapidly killed hundreds trapped inside it.

Grenfell Tower in the U.K. is one of the recent fires that comes to mind. It occurred in June 2017, killing 72 people, while 74 residents were hospitalized for non-fatal injuries. Grenfell Tower was designed to be operated under a “stay put policy” in the event of a fire, assuming a complete evacuation would never be necessary. The building was not sprinklered or provided with a fire alarm system and only had a single central exit stairwell. The residents were trapped in the building as it had only one exit, and corridors were obstructed with rubbish, such as old mattresses.

A means of egress is required to provide an unobstructed and continuous path of travel from any point in a building to leave buildings, structures, and spaces. A means of egress is comprised of access to exit, exit, and exit discharge.

The NBC permits a single exit for a building that is two storeys high with other conditions. For example, for a non-sprinklered building serving a Group C occupancy (other than those regulated by Part 9 and dwelling units opening to the exterior), a single exit is permitted for a 100 m² (1,076 sf) maximum floor area and where the travel distance is a maximum of 15 m (49 ft). For a sprinklered building serving a Group C occupancy, a maximum floor area of 150 m² (1,615 sf) floor area and a travel distance to exit not more than 25 m (82 ft) is applicable.

Building and life safety codes used in other countries permit a single exit in buildings under specific conditions. Examples include the National Fire Protection Association, Life Safety Code (NFPA 101), International Building Code (IBC), Australian, New Zealand, and British codes. It is not practical to include the foundational principles of every prescription contained in these codes; therefore, this piece decrypts major different requirements of NFPA, IBC, and Australian codes in a tabular format for the quick understanding of the reader.

Decoding National Construction Code (NCC) of Australia

This broad comparison and analysis is limited to exits and some of the few related issues.

The premises of the pending NBC proposal to consider including a single exit for residential occupancies, Group C, up to three storeys for Part 9 buildings of the NBC and up to six storeys is the following:

• Total occupant load served by the exit is not more than 60
• The number of dwelling units on each storey is limited to four, and the floor area of each unit is not more than 150 m² (1,614 sf)
• The building is sprinklered throughout
• The building is equipped with a fire alarm system

The current NBC permits a single exit for residential occupancies with specific prescriptions.

Australia’s National Construction Code (NCC) permits a single exit from each storey if specific conditions are met. For Class 2 buildings, in addition to any horizontal exit, at least two exits are required from each storey if the building has an effective height of more than 25 m (82 ft); however, it does not apply to a part of a storey that is provided with direct egress to a road or open space. For a single exit, the travel distance requirements apply. Regarding travel distance for Class 2 buildings, the entrance doorway is to be a maximum of 6 m (19 ft) from an exit or from a point from which travel in different directions to two exits is available or 20 m (65 ft) from a single exit serving the storey at the level of egress to a road or open space.

In addition, single exit requirements are to be directly compared with the related construction provisions listed in the code. For example:

1. a) Construction is to be Type A, meaning noncombustible construction, except for Type C, which is combustible for a two-storey building with at least two exits.
2. b) Fire resistance level (FRL)—Structural adequacy (min)/integrity (min)/insulation (min) for the loadbearing walls of a stair must be 90/90/90 and -/60/60 for non-loadbearing.
3. c) FRL between two sole-occupancy units is 90/90/90 for loadbearing and -/90/90 for non-loadbearing.
4. d) FRL for a public corridor is 90/90/90 for loadbearing and -/60/60 for non-loadbearing.
5. e) FRL for a floor assembly is 90/90/90.
6. f) An automatic sprinkler system is not required for a building up to six storeys—assuming each storey is 3 m (10 ft).

The palpable evidence demonstrated above, the Australian code undeniably allows a single exit; however, its tone and tenor, fabric, texture, grammar, flavour, concept, and architecture do not, without a doubt, resonate with the principal tenet and philosophy of the current NBC. The two codes exhibit gaps in the type of construction, fire-resistance level of the floor, roof, internal and external walls, public corridor, automatic sprinkler requirement for a three-storey high building, and travel distance; therefore, cherry-picking a portion of the code may lead to unpredictable consequences.

The 2021 edition of the IBC permits a single exit in buildings not more than two storeys high (also permitted for three-storeys high apartment buildings—Group R2) combined with not exceeding a maximum number of occupants in the space/storey and meeting a maximum travel distance to the exit. Such criteria vary for each occupancy group. For example, given that Group R2 occupancies are always required to be sprinklered, the IBC allows a single exit to extend up to three storeys above grade, where the floor contains up to four dwelling units and the maximum travel distance to the exit is not more than 38 m (124 ft).

The single exit criteria in the IBC assumed the risk of exit blockage in case of emergency is insignificant if the storey is relatively close to the level of exit discharge and limited in size, the travel distance to exit is short, and the number of occupants is limited. The 2021 edition of NFPA 101 generally requires no less than two exits to be provided for the space/storey where the occupant load is not more than 500. Still, it contains detailed criteria that need to be met to allow for a single exit in a storey and does not extend to all occupancies. Storeys containing new educational occupancies are to be provided with two exits, while other occupancies must be provided with access to not less than two exits from the storey. However, in comparing the single exit criteria applicable to new apartment buildings in NFPA 101 with those in the IBC, NFPA 101 applies the common path of travel threshold, but the total number of storeys in the new apartment building is increased to four; but the following restrictions apply:

• The exit stairway does not serve more than one-half storey below the level of exit discharge.
• Travel distance from the dwelling unit entrance to the exit is not more than 10.7 m (35 ft).
• Specific fire resistance-rated separation requirements are met for exit stairways, corridors, and for separation between dwelling units.

NFPA 101 evaluated risk factors beyond those in the IBC as they may affect the reliability of a single exit allowance. As such, building designers required to comply with NFPA 101 must carefully evaluate the basis of compliance with single exit requirements compared to the IBC.

Conclusion

The proposal to include a single exit without credible research specific to the Canadian codes defies the essential structural chemistry of an evacuation mechanism. The precursor to two minimum exits is that an alternative exit is available if one exit is blocked by smoke or fire during an emergency. What does the design want to accomplish, and what auditable benefits must be diagnosed first? A proposal to permit a single exit should demonstrate a saving in cost or improve the landscape of the building or any other visible benefits. It is not enough to proceed with a change without careful evaluation of these impacts. As narrated and comparison formulated in the sidebars, the Australian, NFPA, and IBC codes are distinctively different from NBC, and thus, to include these provisions, additional analysis and re-configuration of the provisions may be required to avoid unintended consequences.

Different requirements between National Building Code of Canada (NBC) and Australia’s
National Construction Code (NCC)

 

Item	Description of items for a residential occupancy, three- and six-storey buildings	NBC 2020	NCC (2022)
1.0	Definition and classification	Residential occupancies are classified as Group C, used by persons for whom sleeping accommodation is provided. It includes hotels, motels, boarding and lodging, construction camps, etc.	A building containing two or more sole-occupancy units each—being a separate dwelling classified as Class 2. Sole-occupancy unit means a room or other part of a building for occupation by one or joint owner, lessee, tenant, or other occupier to the exclusion of any other owner, lessee, tenant, or other occupier and includes a dwelling. It does not include hotels.
2.0	Construction type	NBC allows combustible, noncombustible, used singly or in combination. NBC permits encapsulated mass timber construction for sprinklered buildings.	Australian code classifies construction into three types; Type A, the most fire-resistant; Type B, and Type C, the least fire-resistant.   Type A—materials that have a low contribution to fire hazard. These materials include concrete, masonry, and non-combustible steel. Type C—materials that have the least fire resistance. These include combustible construction. Type A—NCC is required for the three- and six-storey buildings containing sole-occupancy units. Type C—combustible construction for Class 2 buildings up to two storeys, provided it has access to at least two exits or its own direct access to road or open space.
2a	Floor assembly (fire-resistance rating [FRR])	Floor assemblies are to be fire-separated with a required FRR of 60 or 45 minutes, depending on the type of construction and if a building is sprinklered or not.   NBC does not separate the time needed to withstand flame passage, heat transmission, and temperature maintenance.	Structural adequacy (min)/Integrity (min)/Insulation (min) (Fire-resistance level [FRL])—90/90/90.
2b	Roof assembly (FRR)	Roof assemblies are to have a FRR of 60 minutes in certain instances.	Structural adequacy/Integrity/Insulation (FRL)—90/60/30
2c	Loadbearing internal walls and columns (FRR)	These are to have a FRR not less than that required for the supported assembly.	Structural adequacy/Integrity/Insulation (FRL)—90/-/-
2d	Loadbearing external walls–most stringent condition (FRR)	These are to have a FRR not less than that required for the supported assembly.	Structural adequacy/Integrity/Insulation (FRL)—90/90/90
3.0	Spatial separation	Spatial separation depends on the building’s use, the maximum area of an exposed building face, and the percentage of allowed unprotected openings.	To avoid spread of fire between buildings on adjoining allotments, this is verified by limiting heat flux based on their locations within the boundaries of an adjoining property. For example, for the building’s location on the boundary, heat flux limit is 80 kW/m2.
4.0	FRR of fire separation between suites	It is 45 minutes FRR for a three-storey building and 45 minutes or 60 minutes depending on the fire-resistance rating of the assembly above it.	Structural adequacy/Integrity/Insulation (FRL)—90/90/90 for load bearing and -/90/90 for non-loadbearing walls.
5.0	Public corridor-fire separation between it and the remainder of the storey	It is to have a minimum FRR of 45 min.	Structural adequacy/Integrity/Insulation (FRL)—90/90/90 for load bearing and -/60/60 for non-loadbearing.
6.0	Vertical shaft FRR	It is to be fire-separated with a minimum FRR of 45 minutes.	Structural adequacy/Integrity/Insulation (FRL)—90/90/90 for load bearing and -/90/90.
7.0	Electrical room FRR	For a storey that is not sprinklered throughout, FRR is 60 minutes. For a sprinklered building, a fire separation is not required (dependent on equipment).	A FRL of no less than 120/120/120 for a room containing emergency equipment operating in an emergency.
8.0	Automatic sprinkler system	It is not required for a three-storey building. For others, it depends on the type of construction, building area, and the building height. It is required for using encapsulated mass timber construction.	For a Class 2 building, sprinklers are required throughout the whole building if any part of the building is four storeys or more and an effective height is not more than 25 m (82 ft).
9.0	Fire alarm system	It is to be installed in buildings with an automatic sprinkler system, except for buildings with fewer than nine sprinklers. A fire alarm system is required in a building greater than three storeys, including the storey below the first storey or where a residential occupancy with sleeping accommodation of more than 10 is provided. Other conditions/exceptions also apply.	An automatic smoke detection and alarm system is to be provided in a Class 2 building or part of a building.
10.0	Fire separation of exit FRR	It is to be a minimum of 60 minutes but not less than 45 minutes if the floor assembly above the storey is 45 minutes.	For three- and six-storeys it is 90/90/90/ for loadbearing and -/60/60/ for nonloadbearing walls for exit stairs with common walls.
11.0	Maximum travel distance to an exit	For a building with two exits, it is 45 m (147 ft) for a sprinklered building and 30 m (98 ft) for a non-sprinklered building.	The entrance doorway of any sole-occupancy unit is to be not more than 6 m (20 ft) from an exit or from a point from which travel in different directions to two exits is available; or 20 m (65 ft) from a single exit serving the storey at the level of egress to a road or open space; and no point on the floor of a room which is not in a sole-occupancy unit is more than 20 m (65 ft) from an exit or from a point at which travel in different directions to two exits is available.
12.0	Number of exits	Every floor area intended for occupancy must be served by at least two exits. A single exit is permitted based on specified conditions such as building height, occupant load, floor area, and travel distance.	Every building is to have at least one exit from each storey.   Class 2 buildings, in addition to horizontal exit, at least two exits are provided from each storey if the building has an effective height of more than 25 m (82 ft). However, the above requirements do not apply to part of a storey that is provided with direct egress to a road or open space; and for a single exit, the travel distance requirements mentioned in Row 11 are met. (Refer to row two for two exits in Type C construction)
13.0	Emergency lighting	Emergency power for lighting is to be designed and installed so upon failure of the regular power, it will assume the electrical load automatically for 30 minutes.	An emergency lighting system is to operate at the minimum required level of illuminance for at least 90 minutes.

 

Different requirements between National Building Code of Canada (NBC) and Australia’s National Construction Code (NCC) continued

National Fire Protection Association, Life Safety Code (NFPA 101) compared to International Building Code (IBC)

Item	Description of items for residential occupancy, three- and six-storey buildings	National Fire Protection Association, Life Safety Code (NFPA 101), 2021	International Building Code (IBC), 2021
1.0	Definition and classification	New apartment building definition: A building or a portion of a building containing three or more dwelling units with independent cooking and bathroom facilities.	Group R-2 (apartment houses) undefined.
2.0	Construction type	Not specified	Depending on height, area, and other requirements, allowance ranges from Type I to type V.
2a	Floor assembly (fire-resistance rating [FRR])	Not specified	Ranges from 2 to 0 hours, depending on the applicable construction type.
2b	Roof assembly (FRR)	Not specified	Ranges from 1.5 to 0 hours, depending on the applicable construction type. Exemptions apply.
2c	Loadbearing internal walls and columns (FRR)	Not specified	Ranges from 3 to 0 hours, depending on the applicable construction type. Conditions that allow FRR apply.
2d	Loadbearing external walls—most stringent condition (FRR)	Not specified	Ranges from 3 to 0 hours, depending on the applicable construction type. Conditions apply.
3.0	Spatial separation	Not specified	External wall fire resistance rating ranges between 1 and 0 hours, depending on fire separation distance and construction type. Per cent of unprotected openings restriction apply where the required FRR is 1 hour.
4.0	FRR of fire separation between suites	0.5 hour (sprinklered building)	1-hour FRR (required construction type IA to IIA) 0.5 hour FRR (construction type IIB to VB)
5.0	Exit access corridor-fire separation between it and the remainder of the storey	0.5 hour (sprinklered building)	0.5 hour (sprinklered building)
6.0	Vertical shaft FRR	2 hours (height > 3 storeys) 1 hour (height ≤ 3 storeys)	2 hours (height > 3 storeys) 1 hour (height ≤ 3 storeys except if FRR of Floors required > 1 hour)
7.0	Electrical room FRR	Not specified	Applicable if required by NFPA 70
8.0	Automatic sprinkler system	Mandatory in all buildings	Mandatory in all buildings
9.0	Fire alarm system	Required in buildings where height ≥ 4 storeys	Required where any of the following conditions exist: •Dwelling units ≥ 3 storeys above lowest exit level •Dwelling units > 1 storey below height exit level serving the unit
10.0	Fire separation of exit FRR	2 hours (height > 3 storeys) 1 hour (height ≤ 3 storeys)	2 hours (height > 3 storeys) 1 hour (height ≤ 3 storeys)
11.0	Maximum travel distance to an exit	61 m (200 ft) from dwelling unit entrance door to exit (sprinklered buildings)	76 m (250 ft)
12.0	Emergency lighting	Required where height ≥ 4 storeys or where number of dwelling units	Required in buildings required to have 2≥ exits
13.0	Number of exits	Not less than two for occupant load ≤ 500 One is permitted where: •Number of storeys ≤ 4 •Number of dwelling units ≤ 4 per storey •The building is sprinklered •Stair does not go more than half storey below exit level •Travel distance from unit entrance door to exit ≤ 10.7 m (35 ft) •Corridor FRR ≥ 1 hour •Stairway enclosure FRR ≥ 1 hour •Stairway door FPR ≥ 1 hour	Not less than two for occupant load ≤ 500 One is permitted where: •Number of storeys ≤ 3 •Number of dwelling ≤ 4 storey •Maximum travel distance to exit 38 m (125 ft)

 

Authors

Avinash Gupta, P.Eng., is a building code engineer at AG Building and Fire Protection Engineers in Ontario. He is
an active member of code development committees like Use and Egress. His responsibilities include helping professionals and others understand building codes and finding alternative solutions that meet the code’s objectives. His ability to provide these alternative solutions is a testament to his problem-solving skills and can be reached via email at [email protected].

Mohamed S. Mohamed, P.E., P.Eng., is a manager and senior fire and life safety consultant for Jensen Hughes in Riyadh, KSA. Prior to joining Riyadh office, he worked for Jensen Hughes in Canada where he provided code consulting and alternative compliance consulting services. Mohamed occasionally participates in co-authoring life safety articles.

Dominic Esposito, P.Eng., is a manager and senior project consultant (code consulting/fire protection) for Jensen Hughes in Ottawa. His role is to provide clients with cost-effective solutions that maintain their overall design objectives while maintaining safety. The solutions are for the fire and life safety and accessibility requirements of the codes.

Exit discharge path within stairs.

Photo ©ambrozinio/courtesy Bigstockphoto.com

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