Proposed National Building Code Changes for Encapsulated Mass Timber Buildings

Mass timber construction is a fast-emerging method in the construction industry, both in Canada and abroad; unsurprisingly, proposed regulatory changes to expand its use have therefore been the subject of significant interest and discussion within the industry. In particular, the proposed regulatory changes will bring greater alignment amongst Canadian model codes, with the goal of fostering harmonization between the national and provincial codes on the use of mass timber. Below, we review these proposed changes, and provide our takeaways on the awaited development of mass timber as an alternative method of construction.

Background

Mass timber buildings, which are easily spotted by their wooden aesthetic and biophilic design, use thick layers of engineered wood as structural load-bearing components such as beams, columns, and panels. In recent years, mass timber has received increased attention due to its role in sustainable construction (i.e. via the embodied carbon stored in the timber and the responsible forestry practices used as part of the manufacturing process), coupled with the cost and time efficiencies flowing from the increased use of prefabricated mass timber products. As a result, the adoption of mass timber construction continues to rise.[1]

In fact, the number of mass timber projects has increased two-fold since 2015, coinciding with changes to the National Building Codes (which, as discussed below, include a building code, fire safety code, and others), and in particular, the inclusion of permitted height allowances of up to six storeys for mass timber projects; in 2020, this was increased to a permitted height of up to 12 storeys.[2]

The Regulatory Landscape

However, the regulatory regime continues to evolve, portending more changes on the horizon for mass timber. In particular, the National Research Council (“NRC“) – a Federal Crown Corporation – publishes model codes (including a building code, fire safety codes, and plumbing and energy codes) for adoption by provincial and territorial authorities. Provinces and territories can then adopt these model codes in their entirety and modify them as they see fit, or they can publish their own independent code(s) that may or may not be based on the national model code(s). Manitoba, Saskatchewan, New Brunswick, Nova Scotia, Prince Edward Island, and the Territories have all adopted these model codes, while British Columbia, Alberta, Ontario, and Quebec have published their own independent codes.[3]

Earlier this year, the Canadian Board for Harmonized Construction Codes (“CBHCC”) hosted a public comment period led by the Joint Task Group for Harmonized Variations for Mass Timber (“JTG-HVMT”), which includes the provinces of British Columbia, Ontario and Quebec, on proposed changes to the National Building Code (the “NBC”) in relation to encapsulated mass timber construction (“EMTC”). The proposed changes were developed on an expedited basis to meet provincial needs and will be considered by the CBHCC after feedback has been analyzed and next steps are determined.

The CBHCC is made up of representatives from provincial, territorial, and federal public services and is responsible for developing the National Model Codes, which are subsequently published by the NRC. The CBHCC provides a forum for the provinces to provide input with respect to proposed changes to a given model code, so as to promote the harmonization of codes between jurisdictions. Notably, this is a rare instance of a province-driven proposal being hosted by the CBHCC and represents a noteworthy change in the code development process that (1) appears to be more responsive to provincial priorities and (2) creates consistency amongst various codes across Canada’s jurisdictions.[4]

In short, there appears to be a broad consensus at the provincial and federal level to expand the use of mass timber in order to allow for greater building occupancy, allow for taller mass timber buildings, and varying encapsulation requirements dependent on the building archetype and height.

Key Proposed Changes

In relevant part the key proposed changes to the NBC relate to Encapsulated Mass Timber Construction (“EMTC“). Under the NBC, EMTC is defined as the “type of construction in which a degree of fire safety is attained by the use of encapsulated mass timber elements with an encapsulation rating[5] and minimum dimensions for structural members and other building assemblies”. This often translates to a lower quantity of exposed wood surfaces, but greater levels of fire protection, as the limiting of exposed surfaces will delay ignition and combustion.

By contrast, EMTC is different than two other widely-known mass timber construction methods, known as “combustible construction”[6] and “heavy timber construction”[7]. Both combustible construction and heavy timber construction, which often have larger areas of timber exposure, each only stipulate a fire resistance rating of under 45 minutes, which mean that they fall below the degree of fire protection required of EMTC. In other words, combustible construction and heavy timber construction offer less fire safety protection than EMTC; as a result, they pose a greater hazard than EMTC, and are more restricted in their usability. In particular, these two types of construction have a lower permissible storey height in order to ensure compliance with fire safety standards, but provide some flexibility through the availability of larger areas of exposed timber surfaces.

In summary, the proposed changes to the NBC would permit EMTC to be employed in (i) buildings up to 18 storeys with a 70-minute minimum encapsulation rating, (ii) buildings up 12 storeys with a 50-minute minimum encapsulation rating, and/or (iii) buildings up to 6 storeys with a 0-minute encapsulation rating – across 7 new building “archetypes”.[8]

There are 6 proposed changes in total:

• EMTC Proposed Change 01: EMTC, Various Heights and Occupancy Types, Sprinklered — New Construction Article Summarizing All EMTC Building Types. This proposal introduces changes to several new building archetypes and to reflect the increase of maximum building heights, along with sprinkler requirements for all proposed buildings.
• EMTC Proposed Change 02: Encapsulation of Mass Timber Elements — Encapsulation of Mass Timber Elements. This proposal introduces two other encapsulating ratings, being 0-minute and 70-minute ratings, which are now in addition to the existing 50-minute rating for EMTC.
• EMTC Proposed Change 03: Encapsulation Materials — Prescriptive Option for 70 min Encapsulation Rating. This proposal allows for the 70-minute encapsulation rating to be achieved through the construction of two layers of 5/8″ Type X gypsum wallboards.
• EMTC Proposed Change 04: Encapsulation Cladding — Tiered permissions for combustible cladding. This proposal introduces the types of cladding to be used on the exterior wall of an EMTC building, and specifically the allowance of 100% combustible cladding where the building is less than 4 storeys – and lower cladding permissions as the building height increases.
• EMTC Proposed Change 05: Major Occupancy Fire Separations — Removal of requirements for higher fire-resistance rating (FRR) in EMTC major occupancy separations. This proposal removes existing requirements for higher fire-resistance rating in major occupancy fire separations of EMTC buildings, on the basis that such requirements are outdated and inconsistent with modern fire safety principles.
• EMTC Proposed Change 06: Additional Requirements for EMTC — Revised measures for protection of EMTC during construction. This proposal defines the requirements related to the construction and assembly of encapsulated mass timber projects, and standards related to exposed surfaces during the construction phase.

These proposals are based on the International Building Code (“IBC”) 2021 elements, and the existing historical limits for buildings and fire safety principles in practice from the NBC. The joint task force had also independently commissioned a transferability report to compare the EMTC provisions in the IBC and their applicability to the Canadian context. The transferability report concluded that the NBC can adopt some of the fire and structural provisions with a handful of conservative modifications. By way of example, the IBC recommends that IV-B (Mass timber protected exterior, limited exposed timber interiors) allow for 100% mass timber ceilings and integral beams, whereas the NBC continues to require no more than 25% exposure of similar areas.

Takeaways

As focus shifts towards greater Environmental-Social-Governance (ESG) goals, more businesses are considering sustainable construction materials in their construction plans. EMTC is likely to gain further traction following the 28^th Conference of the Parties to the UN Framework Convention on Climate Change (commonly known as “COP28”, which was held in November and December of 2023 in Dubai) as the environmental and financial benefits of building with mass timber continue to offer an appealing avenue for the various jurisdictions to explore in order to meet those requirements.

These proposed changes collectively improve the viability of EMTC as a viable construction method by establishing clear performance criteria, and it therefore stands to reason that it will encourage even wider adoption of EMTC in future Canadian projects. This will naturally be of interest to the construction industry as a whole, including those seeking low carbon alternatives to traditional construction materials and methods at a time when the regional, national, and international markets continue to struggle through supply chain disruptions and material shortages.

The JTG-HVMT public review and consultation closed on February 16, 2024. Subject to comments received, these changes are expected to be adopted by provinces as early as spring 2024. As of now, Ontario has not decided whether to adopt the proposed changes based on this initiative, and the province will likely undertake a technical review of the proposed changes. We await with interest to see how Ontario and other provinces proceed with this initiative.

[1] According to the 2021 State of Mass Timber Buildings in Canada Report, there were nearly 800 mass timber projects built or under construction across Canada as of 2021: https://cfs.nrcan.gc.ca/publications?id=40364.

[2] National Building Code, Division B Part 3 Fire Protection, Occupant Safety and Accessibility, s. 3.1.6 Encapsulated Mass Timber Construction.

[3] For example, the Ontario Building Code incorporates approximately 60% of the NBC.

[4] In this context, “public review” refers to members of the public submitting comments/feedback, via an online portal, on each of the proposed changes, including whether they should be approved, altered (and if so, how), or rejected.

[5] Under the NBC, the “encapsulation rating” is the amount of time that a material or assembly will delay the ignition and combustion of encapsulated mass timber when it is exposed to fire under specific test conditions and performance criteria.

[6] “Combustible construction” means construction that does not meet the requirements or criteria for (1) “non-combustible construction” as set out in the CAN/ULC-S114 “Standard Method of Test for Determination of Non-Combustibility in Building Materials” or (2) encapsulated mass timber construction.

[7] “Heavy timber construction” means combustible construction in which a degree of fire safety is attained by placing limitations on the sizes of wood structural members and on the thickness and composition of wood floors and roofs and by the avoidance of concealed spaces under floors and roofs.

[8] In essence, an “archetype” – which term does not carry an authoritative definition – is generally understood to refer to a building categorized according to a combination of (1) its function (e.g. residential single family, residential multi-family, office, commercial, etc.), and (2) its occupancy capacities (such as building height and floor/mass ratio, and how many units or individuals can occupy each floor).

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