The National Building Code of Canada (NBC) defines fire safety under Objective OS1: “an objective of this code is to limit the probability that as a result of the design or construction of the building, a person in or adjacent to a building will be exposed to an unacceptable risk of injury due to fire.”

In simpler terms, fire safety is the reduction of the potential for harm to life as a result of fire in buildings. Although the potential for being killed or injured in a fire cannot be completely eliminated, fire safety in a building can be achieved through proven building design features intended to minimize the risk of harm to people from fire to the greatest extent possible.

Designing a building to ensure minimal risk or to meet a prescribed level of safety from fire is more complex than just the simple consideration of what building materials will be used in construction of the building, since all building materials are affected by fire. Many factors must be considered including the use of the building, the number of occupants, how easily they can exit the building in case of a fire and how a fire can be contained.

Even materials that do not sustain fire do not guarantee the safety of a structure. Steel, for instance, quickly loses its strength when heated and its yield point decreases significantly as it absorbs heat, endangering the stability of the structure. An unprotected, conventional cold-formed steel joist floor system will fail in less than 10 minutes under standard laboratory fire exposure test methods, while an unprotected, conventional wood joist floor system can last up to 15 minutes. Reinforced concrete is also not immune to fire. Concrete will spall under elevated temperatures, exposing the steel reinforcement and weakening structural members. As a result, it is generally recognized that there is really no such thing as a fire-proof building.

The NBC only regulates those elements which are part of the building construction. The building contents found in any building are typically not regulated by the NBC, but in some cases they are regulated by the National Fire Code of Canada (NFC).

The occupancy classification of buildings or parts of buildings according to their intended use accounts for:

• the quantity and type of combustible contents likely to be present (potential fire load);
• the number of persons likely to be exposed to the threat of fire;
• the area of the building; and
• the height of the building.

This occupancy classification is the starting point in determining which fire safety requirements apply to a particular building. The occupancy classification of a building within the NBC dictates:

• the type of building construction;
• the level of fire protection; and
• the degree of structural protection against fire spread between parts of a building that are used for different purposes.

Fires can occur in any type of structure. The severity of a fire, however, is contingent on the ability of a construction to:

• confine the fire;
• limit a fire’s effects on the supporting structure; and
• control the spread of smoke and gases.

To varying degrees, any type of construction can be designed as a system (combination of construction assemblies) to limit the effects of fire. This allows occupants sufficient time to escape the building and for firefighters to safely carry out their duties.

Occupant safety also depends on other parameters such as detection, exit paths, and the use of automatic fire suppression systems such as sprinklers. These concepts form the basis of the NBC requirements.

For further information, refer to the following resources:

Wood Design Manual (Canadian Wood Council)

Fire Safety Design in Buildings (Canadian Wood Council)

National Building Code of Canada

National Fire Code of Canada

CSA O86, Engineering design in wood

Fitzgerald, Robert W., Fundamentals of Fire Safe Building Design, Fire Protection Handbook, National Fire Protection Association, Quincy, MA, 1997.

Watts, J.M. (Jr); Systems Approach to Fire-Safe Building Design, Fire Protection Handbook, National Fire Protection Association, Quincy, MA, 2008.

Rowe, W.D.; Assessing the Risk of Fire Systemically ASTM STP 762, Fire Risk Assessment, American Society for Testing and Materials, West Conshohocken, PA, 1982.

Flame spread is primarily a surface burning characteristic of materials, and a flame-spread rating is a way to compare how rapid flame spreads on the surface of one material compared to another.

Flame-spread rating requirements are applied in the National Building Code of Canada (NBC) primarily to regulate interior finishes.

Any material that forms part of the building interior and is directly exposed is considered to be an interior finish. This includes interior claddings, flooring, carpeting, doors, trim, windows, and lighting elements.

If no cladding is installed on the interior side of an exterior wall of a building, then the interior surfaces of the wall assembly are considered to be the interior finish, for example, unfinished post and beam construction. Similarly, if no ceiling is installed beneath a floor or roof assembly, the unfinished exposed deck and structural members are considered to be the interior ceiling finish.

The standard test method that the NBC references for the determination of flame spread ratings is CAN/ULC-S102, published by ULC Standards.

Appendix D-3 of the NBC, Division B, provides information related to generic flame-spread ratings and smoke developed classifications of a variety of building materials.

Information is only provided for generic materials for which extensive fire test data is available (refer to Table 1 below). For instance, lumber, regardless of species, and Douglas fir, poplar, and spruce plywood, of a thickness not less than those listed, are assigned a flame-spread rating of 150.

In general, for wood products up to 25 mm (1 in) thick, the flame-spread rating decreases with increasing thickness. Values given in the Appendix D of the NBC are conservative because they are intended to cover a wide range of materials. Specific species and thicknesses may have values much lower than those listed in Appendix D.

The American Wood Council has additional information in their Design for Code Acceptance publication, DCA 1 Flame Spread Performance of Wood Products for the U.S.

Normally, the surface finish and the material to which it is applied both contribute to the overall flame-spread performance. Most surface coatings such as paint and wallpaper are usually less than 1 mm thick and will not contribute significantly to the overall rating.

This is why the NBC assigns the same flame-spread and smoke developed rating to common materials such as plywood, lumber and gypsum wallboard whether they are unfinished or covered with paint, varnish or cellulosic wallpaper.

There are also special fire-retardant paints and coatings that can substantially reduce the flame-spread rating of an interior surface. These coatings are particularly useful when rehabilitating an older building to reduce the flame-spread rating of finish materials to acceptable levels, especially for those areas requiring a flame-spread rating no greater than 25.

In general, the NBC sets the maximum flame-spread rating for interior wall and ceiling finishes at 150, which can be met by most wood products.

For example, 6 mm (1/4 in) Douglas Fir plywood may be unfinished, painted, varnished or covered with conventional cellulosic wallpaper. This has been found to be acceptable on the basis of actual fire experience.

This means that in all areas where a flame-spread rating of 150 is permitted, the majority of wood products may be used as interior finishes without special requirements for fire-retardant treatments or coatings.

In a room fire, the flooring is usually the last item to be ignited, since the coolest layer of air is near the floor. For this reason, the NBCC, like most other codes, does not regulate the flame-spread rating of flooring, with the exception of certain essential areas in high buildings:

• exits;
• corridors not within suites;
• elevator cars; and,
• service spaces.

Traditional flooring materials such as hardwood flooring and carpets can be used almost everywhere in buildings of any type of construction.

For further information, refer to the following resources:

Wood Design Manual (Canadian Wood Council)

Fire Safety Design in Buildings (Canadian Wood Council)

National Building Code of Canada

National Fire Code of Canada

CSA O86, Engineering design in wood

CAN/ULC-S102 Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies

American Wood Council

Table 1 : Assigned flame-spread ratings and smoke developed classifications

Surface Flammability and Flame-spread Ratings

In the National Building Code of Canada (NBC) “fire-resistance rating” is defined in part as: “the time in minutes or hours that a material or assembly of materials will withstand the passage of flame and the transmission of heat when exposed to fire under specified conditions of test and performance criteria…”

The fire-resistance rating is the time, in minutes or hours, that a material or assembly of materials will withstand the passage of flame and the transmission of heat when exposed to fire under specified conditions of test and performance criteria, or as determined by extension or interpretation of information derived therefrom as prescribed in the NBC.

The test and acceptance criteria referred to in the NBC are contained in a standard fire test method, CAN/ULC-S101, published by ULC Standards.

Horizontal assemblies such as floors, ceilings and roofs are tested for fire exposure from the underside only. This is because a fire in the compartment below presents the most severe threat. For this reason, the fire-resistance rating is required from the underside of the assembly only. The fire-resistance rating of the tested assembly will indicate, as part of design limitations, the restraint conditions of the test. When selecting a fire-resistance rating, it is important to ensure that the restraint conditions of the test are the same as the construction in the field. Wood-frame assemblies are normally tested with no end restraint to correspond with normal construction practice.

Partitions or interior walls required to have a fire-resistance rating must be rated equally from each side, since a fire could develop on either side of the fire separation. They are normally designed symmetrically. If they are not symmetrical, the fire-resistance rating of the assembly is determined based on testing from the weakest side. For a loadbearing wall, the test requires the maximum load permitted by design standards be superimposed on the assembly. Most wood-stud wall assemblies are tested and listed as loadbearing. This allows them to be used in both loadbearing and non-loadbearing applications.

Listings for loadbearing wood stud walls can be used for non-loadbearing cases since the same studs are used in both applications. Loading during the test is critical as it affects the capacity of the wall assembly to remain in place and serve its purpose in preventing fire spread. The strength loss in studs resulting from elevated temperatures or actual burning of structural elements causes deflection. This deflection affects the capacity of the protective wall membranes (gypsum board) to remain in place and contain the fire. The fire-resistance rating of loadbearing wall assemblies is typically lower than that of a similarly designed non-loadbearing assembly.

Exterior walls only require rating for fire exposure from within a building. This is because fire exposure from the exterior of a building is not likely to be as severe as that from a fire in an interior room or compartment. Because this rating is required from the inside only, exterior wall assemblies do not have to be symmetrical.

The NBC permits the authority having jurisdiction to accept results of fire tests performed according to other standards. Since test methods have changed little over the years, results based on earlier or more recent editions of the CAN/ULC-S101 standard are often comparable. The primary US fire-resistance standard, ASTM E119, is very similar to the CAN/ULC-S101 standard. Both use the same time-temperature curve and the same performance criteria. Fire-resistance ratings developed in accordance with ASTM E119 are usually acceptable to Canadian officials. Whether an authority having jurisdiction accepts the results of tests based on these standards depends primarily on the official’s familiarity with them.

Testing laboratories and manufacturers also publish information on proprietary listings of assemblies which describe the materials used and assembly methods. A multitude of fire-resistance tests have been conducted over the last 70 years by North American laboratories. Results are available as design listings or reports through:

• APA
• Intertek
• QAI Laboratories
• PSF Corporation
• Underwriters’ Laboratories of Canada
• Underwriters’ Laboratories Incorporated

In addition, manufacturers of construction products publish results of fire-resistance tests on assemblies incorporating their proprietary products (for example, the Gypsum Association’s GA-600 Fire Resistance Design Manual).

The NBC contains generic fire-resistance rating information for wood assemblies and members. This includes fire and sound resistance tables describing various wall and floor assemblies of generic building materials that assign specific fire-resistance ratings to the assemblies. Over the last two decades a number of large research projects were conducted at the National Research Council of Canada (NRC) on light-frame wall and floor assemblies, looking at both fire resistance and sound transmission. As a result, the NBC has hundreds of different wall and floor assemblies with assigned fire-resistance ratings and sound transmission ratings. These results are published in the NBC Table A-9.10.3.1.A. Fire and Sound Resistance of Walls and NBC Table A-9.10.3.1.B Fire and Sound Resistance of Floors, Ceilings and Roofs. Not all assemblies described were actually tested. The fire-resistance ratings for some assembles were extrapolated from fire tests done on similar wall assemblies. The listings are useful because they offer off-the-shelf solutions to designers. They can, however, restrict innovation because designers use assemblies which have already been tested rather than pay to have new assemblies evaluated. Listed assemblies must be used with the same materials and installation methods as those tested.

The previous section on fire-resistance ratings deals with the determination of fire-resistance ratings from standard tests. Alternative methods for determining fire-resistance ratings are permitted as well. The alternative methods of determining fire-resistance ratings are contained in the NBC, Division B, Appendix D, Fire Performance Ratings. These alternative calculation methods can replace expensive proprietary fire tests. In some cases, these allow less stringent installation and design requirements such as alternate fastener details for gypsum board and the allowance of openings in ceiling membranes for ventilation systems. Section D-2 in NBC, Division B, Appendix D includes methods of assigning fire-resistance ratings to:

• wood-framed walls, floors and roofs in Appendix D-2.3. (Component Additive Method);
• solid wood walls, floors and roofs in Appendix D-2.4.; and,
• glue-laminated timber beams and columns in Appendix D-2.11.

The most practical alternative calculation method includes procedures for calculating the fire-resistance rating of lightweight wood-frame wall, floor and roof assemblies based on generic descriptions of materials. This component additive method (CAM) can be used when it is clear that the fire-resistance rating of an assembly depends strictly on the specification and arrangement of materials for which nationally recognized standards exist. The assemblies must conform to all requirements in NBCC, Division B, Appendix D-2.3. Wood and Steel Framed Walls, Floors and Roofs.

While the information currently contained in Appendix D-2.4. addresses more historic construction techniques, there has been some resurgence in the use of such assemblies, and the information can be particularly useful when repurposing historic buildings.

NBC, Division B, Appendix D also includes empirical equations for calculating the fire-resistance rating of glue-laminated (glulam) timber beams and columns, in Appendix D-2.11. These equations were developed from theoretical predictions and validated by test results. Large wood members have an inherent fire resistance because:

• the slow burning rate of large timbers, approximately 0.6 mm/minute under standard fire test conditions; and,
• the insulating effects of the char layer, which protects the unburned portion on the wood.

These factors result in unprotected members that can stay in place for a considerable time when exposed to fire. The NBC recognizes this characteristic and allows unprotected wood members, including floor and roof decks, that meet the minimum sizes for heavy timber construction to be used both where a 45-minute fire-resistance rating is required and in many noncombustible buildings. The calculation method in Appendix D determines a fire-resistance rating for glulam beams and columns based on exposure to fire from three or four sides.

The formula for columns or beams which may be exposed on three sides applies only when the unexposed face is the smaller side of a column; no experimental data exists to verify the formula when a larger side is unexposed. If a column is recessed into a wall or a beam into a floor, the full dimensions of the structural member are used in the formula for exposure to fire on three sides. Comparisons of the calculated fire-resistance ratings with experimental results show the calculated values are very often conservative. A designer may determine the factored resistance for a beam or column by referring to CSA O86 Canadian Wood Council’s Wood Design Manual.

As well, the CSA O86 standard includes an informative Annex B that provides a method to calculate fire-resistance ratings for large cross-section wood elements, such as beams and columns of glued-laminated timber, solid-sawn heavy timber and structural composite lumber.

Further information on the calculation of fire resistance of heavy timber members is available in the American Wood Council’s publication Technical Report 10: Calculating the Fire Resistance of Exposed Wood Members (TR10).

For further information, refer to the following resources:

Wood Design Manual (Canadian Wood Council)

Fire Safety Design in Buildings (Canadian Wood Council)

National Building Code of Canada

National Fire Code of Canada

CSA O86, Engineering design in wood

CAN/ULC-S101 Standard Method of Fire Endurance Tests of Building Construction and Materials

ASTM E119 Standard Test Methods for Fire Tests of Building Construction and Materials

American Wood Council

Sultan, M.A., Séguin, Y.P., and Leroux, P.; “IRC-IR-764: Results of Fire Resistance Tests on Full-Scale Floor Assemblies”, Institute for Research in Construction, National Research Council Canada, May 1998.

Sultan, M. A., Latour, J. C., Leroux, P., Monette, R. C., Séguin, Y. P., and Henrie, J. P.; “RR-184: Results of Fire Resistance Tests on Full-Scale Floor Assemblies – Phase II”, Institute for Research in Construction, National Research Council Canada, March 2005.

Sultan, M.A., and Lougheed, G.D.; “IRC-IR-833: Results of Fire Resistance Tests on Full-Scale Gypsum Board Wall Assemblies”, Institute for Research in Construction, National Research Council Canada, August 2002

Heavy timber construction

Performance of Adhesives in Finger-joined Lumber in Fire-resistance-rated Wall Assemblies

Fire Separations & Fire-resistance Ratings

The vulnerability of any building in a fire situation is higher during the construction phase when compared to the susceptibility of the building after it has been completed and occupied. This is because the risks and hazards found on a construction site differ both in nature and potential impact from those in a completed building. And, these risks and hazards are occurring at a time when the fire prevention and protection elements that are designed to be part of the completed building are not yet in place.

For these reasons, construction site fire safety includes some unique challenges. However, an understanding of the hazards and their potential risks is the first step towards fire prevention and mitigation.

It is important to comply with applicable regulations related to fire safety planning during construction, and cooperation between all stakeholders in establishing and implementing a plan goes a long way in reducing the potential risk and impacts of a fire on any construction sites. In addition to province-wide regulations, local governments and municipalities can also have specific laws, regulations or requirements that must be followed. The local fire department can be a resource in directing you to these additional regulations or requirements.

Construction site safety has the potential to impact productivity and profitability at any phase of the project. Given that provincial or municipal regulations provide the minimum requirements for construction site fire safety, consideration should also be given to the specific characteristics, objectives and goals of the project, which could provide incentives to exceed the regulated standards for construction site fire safety. It can be prudent to assess and implement various ‘best practices’, based on the specific needs of your site, which can provide an additional level of protection and build a culture of fire safety.

Most construction site fires can be prevented with knowledge, planning and diligence; and, the impact of those fires that might occur can be significantly lessened. Understanding and addressing both the general and specific hazards and risks of a particular construction site requires education and training, as well as preparedness and continued vigilance.

For further information, refer to the following resources:

• “Construction Site Fire Safety: A Guide for Construction of Large Buildings” – by Centre for Public Safety and Criminal Justice Research, University of the Fraser Valley for CWC, 2015
• “Construction Site Fire Response: Preventing and Suppressing Fires During Construction of Large Buildings” – by Centre for Public Safety and Criminal Justice Research, University of the Fraser Valley, 2015
• “Report on Course of Construction (Fire) Best Practices Guide” – by Technical Risk Services for CWC, 2014
• “Comparison of the Canadian Construction Site Fire Safety Regulations/Guidelines” – by Sereca for CWC, 2014
• Quick Facts – Insurance and Construction Series (CWC, 2005):
  • “No. 1 – Course of Construction Insurance Basics“
  • “No. 2 – Course of Construction Risk Control“
  • “No. 3 – Course of Construction – Site Risk Control Guidelines“

• “Fire Safety and Security: A Technical Note on Fire Safety and Security on Construction Sites in British Columbia” – by Wood Works! British Columbia, 2013
• City of Surrey, BC – Construction Fire Safety Plan Bulletin

• Fire Safety During Construction of Five and Six Storey Wood Buildings in Ontario: A Best Practice Guideline – by Ministry of Municipal Affairs and Housing of Ontario, May 2016
• “Fire Safety and Security: A Technical Note on Fire Safety and Security on Construction Sites in Ontario” – by Wood Works! Ontario, 2013