Can I build it out of wood? Does it need to be sprinklered? What does the fire rating of my floor assemblies, roof assemblies, or mezzanines need to be? In this post, I will discuss how to answer some of these fundamental questions when it comes to Part 3 buildings in Canada.

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Articles 3.2.2.20. to 3.2.2.90. of the Building Code essentially provide various design options for your building, and will answer many fundamental questions such as allowable size, construction type, and sprinkler requirements. Because these Articles determine so much about the building, including type of construction (combustible, noncombustible), they are frequently referred to as “construction articles.”

Construction articles will provide requirements on these items, each of which has its own section in this post:

1. Major occupancies
2. Building height
3. Building area
4. Number of streets facing
5. Sprinklers
6. Construction type (combustible or noncombustible)
7. Structural fire-resistance

If you know the first 4 factors (use, size, streets facing), you can determine the construction article with the minimum requirements. You can also work backwards if, for example, you want to determine the maximum size a building can be without requiring sprinklers or noncombustible construction.

When doing this exercise, it is important to remember that most buildings will fit under more than one construction article, but there will typically be one set of requirements that will be lower than the others; the lowest requirements are the code minimum, and need to be met or exceeded. As long as a building meets all of the requirements of a single construction article, it is considered as code compliant.

In this post I will discuss the basic process I perform to classify simple buildings, and provide some common pitfalls for each section. More complex scenarios, such as multiple major occupancies, are not discussed.

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1. Major Occupancies

The first thing I do when determining construction requirements is to classify the major occupancy (use). The major occupancy of a building is a defined term that means the principal occupancy of the building. Separate major occupancies can also be assigned to individual parts of a building, such as a suite, where there are multiple uses within a building.

The construction articles (3.2.2.20. to 3.2.2.90.) are organized in alphabetical order by the Group and Division of the major occupancies, so classifying the use first will help narrow your search. The Group and Division classifications are provided in Table 3.1.2.1. of the Building Code. For most occupancies, determining the classification is straightforward. Extra caution is needed when dealing with Group B and Group F occupancies.

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Common Pitfall: Subsidiary Occupancies

Some occupancies are considered to be subsidiary to the major occupancy of the building or suite. These non-major occupancies are commonly referred to as subsidiary occupancies, which exist only to serve the major occupancy (i.e. the occupancy would not exist if the major occupancy was removed). A common example is office space within a larger retail or industrial suite – the office space would not exist if it were not for the industrial space.

Subsidiary occupancies are not considered when determining the construction article, but need to be considered for other code requirements where the code refers simply to the “occupancy” of a space (as opposed to the “major occupancy”).

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2. Building Height

Next up is to determine the building height, in number of storeys; the construction articles generally do not depend on the height in metres, thought here are some notable exceptions (Article 3.2.2.50. limits the height from the first storey to the uppermost floor to 18 m for example).

Steps to determining building height:

1. Calculate grade
2. Determine the first storey
3. Count number of storeys from first storey to the top of the building

Grade and first storey are both defined terms:

Grade is the lowest of the average levels of finished ground adjoining the exterior walls on each side of the building.

Confusing? Follow these steps: calculate the average level of finished ground separately for each side; grade is the lowest of these averages.

First storey is the highest storey that is a maximum of 2 m above grade.

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Common Pitfall: Grade Calculation

Grade is defined differently in the Building Code than it is in many zoning bylaws. It is NOT an average of finished ground on all sides of a building.

If grade is determined incorrectly, it can result in an incorrect building height and large differences in construction requirements.

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3. Building Area

Building area is the greatest horizontal area above grade defined by the outside surface of exterior walls, or the centreline of firewalls (if applicable).

To determine building area:

1. Project the outline of all above grade exterior walls onto a single plane
2. Trace the resulting outline of these projections
3. Calculate the area of this new outline

Overhangs from above grade storeys will increase the building area as it is defined in the Building Code.

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Common Pitfalls: Building Area

Building area is not any of the following:

• The gross area of all floors
• The outline of the lowest storey only (unless there are no overhangs in the building)
• Unenclosed balconies and overhangs for roofs are not considered for building area

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4. Number of Streets Faced

All sprinklered buildings only need to face a single street. For unsprinklered buildings, the construction article may require the building to face additional streets to facilitate fire department response. The required number of streets faced will increase with increasing building area.

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Common Pitfall: Determining the number of streets facing

A building is only considered to be facing a street if its principal entrance is between 3 m and 15 m from the street. Additionally, for a building to be facing 2 streets, 50% of its perimeter needs to be within 15 m of a street. For 3 streets, this is increased to 75%. These requirements are given in Article 3.2.2.10. of the Building Code.

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Example: Determining the Construction Article

If you know the size (height and area) and use of the building, you will be able to determine all the construction requirements based on the applicable construction article(s). For unsprinklered buildings, you may also need to know the number of streets facing. There is often a single article with the lowest requirements that will be chosen as the code minimum for the project.

Example: Group C (residential) major occupancy, 3 storeys, 1200 m2 building area

Construction Article – 3.2.2.52. is the code minimum IF the building faces 3 streets. If it does not face 3 streets, the code minimum construction article would be 3.2.2.54. (Group C, up to 3 Storeys, Sprinklered) and the building would need to be sprinklered. Streets facing can be the triggered for requiring sprinklers in a building.

Article 3.2.2.53. cannot be used, since the allowable building area for a 3 storey building is exceeded (see below).

1200m2 is the maximum building area for 3 storey building face 3 streets, under 3.2.2.52.

Building area in example exceeded allowable under Article 3.2.2.53.

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5. Sprinklers

The requirement for sprinklering a building will be stated clearly in one the Sentences in the construction article (it is also typically written in the title of the Article). The code states requirements; it does not state when something is not required, unless it is an exception to a requirement somewhere else in the code. Therefore, if there is no statement that sprinklers are required, the building likely does not need to be sprinklered.

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Common Pitfall: Sprinklers

The need for sprinklers can arise from other parts of the building code as well, most commonly to allow relaxations from other code requirements. Here are some examples of sprinkler relaxations or triggers (outside of the construction article trigger):

• Increased unprotected openings in exterior walls for sprinklered buildings
• Increased travel distances for sprinklered buildings
• Fire code sprinkler requirements depending on storage configurations or other special hazards

Certain municipal bylaws also require sprinklers for certain buildings, so always ensure you check with the local requirements of your project as well. The Vancouver Building By-law requires sprinklers for all newly constructed buildings, with limited exceptions (see 1.3.3.6. of Division A).

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6. Construction Type

The applicable construction article will either state that a building is required to be of noncombustible construction, or that it is permitted to be of combustible or noncombustible construction.

Combustible construction is a permission. Noncombustible construction is a requirement.

The upcoming 2020 National Building Code will contain a new construction type: encapsulated mass timber. The 2018 British Columbia Building Code has already adopted some of these changes for use in select jurisdictions.

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Common Pitfall: Noncombustible construction

Buildings of noncombustible construction are required to be built entirely out of noncombustible materials, unless a specific exemption is provided in the Building Code. A long list of exemptions are provided in Subsection 3.1.5.; however, the exemptions often come with restrictions. For example, combustible interior finishes are permitted within specific thickness and flame-spread rating restrictions, which are different between ceilings and walls.

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7. Structural Fire Resistance

Most construction articles will provide structural fire resistance requirements for floor assemblies, mezzanines, roof assemblies, and loadbearing assemblies. Occasionally there will be no structural fire-resistance requirements for one or more of these assembly types. In some rare cases, there are no structural fire-resistance requirements (see Article 3.2.2.27.).

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Common Pitfalls: Fire-Resistance Ratings

Occupied roof assemblies need to be provided with a fire-resistance rating based on the requirements for floor assemblies, per Article 3.2.2.13.

Some construction articles will require a fire-resistance rating for combustible assemblies, but no rating for noncombustible assemblies (see below).

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Now You Know (The Basics)!

This post provides some basic information on how buildings are classified in the Canadian building codes and highlights some pitfalls that I see frequently that can have big consequences on your project’s construction requirements. I hope it was helpful, particularly for those of you new to navigating these complex documents.

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