The new Ontario Building Code is released, effective January 1, 2025, and the three-month grace period is behind us.

These changes were long anticipated, with the Ontario Government first announcing their intentions last April (2024). Among the latest changes is an increase in the permissible height of encapsulated mass timber construction (EMTC) from 12-storeys to up to 18-storeys for certain occupancies. A significant driver behind this change is the province-wide need for affordable housing, as well as to support local forestry and manufacturing industries.

The benefits of mass timber are clear – quieter and faster construction, with less embodied carbon than traditional building materials – but the lack of familiarity around this material has limited its adoption in modern construction. Historically, “Heavy Timber Construction” has been widely accepted in the codes but its application has been limited to shorter buildings requiring lower fire resistance ratings. Over the past two decades, there has been extensive testing of mass timber structures, both with and without encapsulation assemblies, to determine acceptable safety thresholds that would allow for its use more broadly. That testing led to an update to the National Building Code for 2020, and the changes were subsequently adopted by British Columbia (2024) and now Ontario (2025).

The new Ontario Building Code aligns the province with the changes to the National Building Code and similar amendments in other provinces and US States. It acknowledges and welcomes the possibilities that EMTC can offer local markets − an increase in safe, sustainable, and scalable mass timber adoption in our built environment.

What has changed exactly?

The changes to EMTC are classified by major occupancy groups (see Figure 1 below). Both multi-unit residential developments (Occupancy Group C, including apartments and hotels), offices and banks (Occupancy Group D) are now permitted up to 18-storeys under the new building code. Additionally, Occupancy Group A-2 (including schools, libraries, and restaurants), a type that was not previously specified in the code for EMTC, is now permitted up to 18-storeys. This typology is one of many new occupancy groups now permissible for EMTC under the new code, including assisted living care facilities (B-3), retail / markets (E), factories, workshops, and labs (F-2), and warehouses / parkades.

While the ability to build to 18-storeys is the prevailing headline since these code changes were announced, there is an argument to be made that the expansion of other typologies that can apply EMTC in Ontario is just as exciting. Another significant change: the new allowance for exposed timber up to eight and nine storeys for Group C and Group D buildings, respectively, and height increases for other occupancies as well.
It’s a lot of change at once – with a lot of potential applications.

Figure 1: Minimum encapsulation requirements of Encapsulated Mass Timber Buildings

The current state of Mass Timber in Ontario.

While this change has only taken effect this year, the market has long anticipated that this change was coming, with several multi-unit residential developments beyond 12-storeys planned around Toronto in particular. Depending on the development, the ability to transition a planned development from 12-storeys to 18-storeys would mean meeting a new minimum encapsulation requirement of 70 minutes. And though the methods of achieving a safe, compliant, and performative mass timber may be different, the structural considerations for a taller building remain similar regardless of the materiality.

So, now that it’s permitted in the code, and if the design expectations are not significantly more than a taller building of a different material type (and the benefits of mass timber are clear), will we see a rush of mass timber buildings in Ontario?

With focussed effort to overcome a few pre-existing challenges, it certainly should.

The reticence surrounding mass timber, particularly in Ontario, and particularly for multi-unit residential buildings, has less to do with what the code allows, and more to do with the implied, associated risks. The knowledge surrounding mass timber in the industry as a whole is simply not as deep as other material types, and there are often concerns around both cost competitiveness and available, constructable solutions. Assumptions about floor-to-floor heights and grids need to be revisited rather than taken for granted from other structural systems. Pricing needs to be conducted holistically to account for reductions in other categories such as finishes, foundations, schedule and other general conditions of construction.

Yet, there are many mass timber developments that are moving forward – across the GTA as well as the province as a whole – projects that ASPECT has first-hand experience with.

How are these mass timber projects becoming a reality? Truth time: mass timber can be price competitive AND constructable. You just need to go about it the right way… with the right team members at the table.

The opportunity.

Despite the misconceptions, this is an exciting time for mass timber in Ontario. The multi-unit residential market, particularly in Toronto, is opening up to other delivery methods, compared to what we’ve seen in recent memory. The local demand for the larger / taller towers (beyond the long-planned, star-chitect associated developments that are already well underway) has diminished. In the midst of this, there are new possibilities to make better use of interesting sites across the city – spaces for infill developments, and for “upzoning”, that allows for a “middle-tier” of housing and “middle-tier” of heights – heights that now also permit the use of EMTC. These sites are located in established communities, on major streets, with existing infrastructure and amenities in desirable neighbourhoods. In turn, this reality is opening up the possibility for a mix of buildings (and building types) that hold the potential to embroider the fabric of the city.

Beyond multi-unit residential developments, the expansion of EMTC possibilities to additional occupancy types holds the potential to incorporate new and exciting design solutions in Ontario that were not previously explored. Daycares, long-term care facilities, schools – these building types all stand to substantially benefit from the material quality associations, physiological and psychological benefits, and biophilic connections offered by mass timber.

And we all stand to benefit from buildings that incorporate materials with lower embodied carbon.

The possibilities are growing.

A new year always signals a call for positivity, resetting us on a course for change that we always wished for ourselves and others. And while our own, personal resolutions may not have made it past January (we always try so hard, though…), the new changes to the Ontario Building Code stand to create a lasting impact on our buildings and our communities. The code allows for it… what will we all choose to do next?

ASPECT has been involved in the design and construction process of mass timber and tall timber projects across Canada – including the first EMTC building constructed in BC. We’re here to help walk you through these new changes as you make decisions for your project, and to apply our multi-faceted understanding of mass timber to help normalize its use in new ways that are equally exciting and pragmatic.