Top 8 changes coming to Ontario Building Code affecting residential construction

The winter holidays are upon us, but what a lot of people don’t realize is that while most people bring in the New Year by blowing party horns, builders brace themselves for changes to the Ontario Building Code (OBC) coming as early as Jan. 1, 2017 that will push up the cost and complexity of building.

Many interim changes will also be phased in during the lead-up to the next edition of the OBC with a proposed in-effect date of January 2019.

So here are four changes coming that affect low-rise residential construction, as well as four that affect high-rise (some affect both) that we think will be of particular interest to builders.

1. Supplementary Standard SB-12 (Energy Efficiency for Housing): SB-12 introduces new prescriptive compliance packages that represent an energy-efficiency improvement in new homes of approximately 15% over the preceding version. Along with this improvement comes the requirement to utilize technologies such as a heat/energy recovery ventilator (HRV/ERV) and drain-water heat recovery (DWHR). SB-12 also permits performance-based compliance utilizing energy modelling software (i.e., HOT2000, REM/Rate) or adoption of voluntary programs (i.e., Energy Star or R2000).

Phase-in date: Jan. 1, 2017

Estimated cost increase per low-rise home: $2,000+

  1. Two-Unit Houses: Changes are proposed to increase the affordability of newly built houses with a secondary unit. These requirements would include permitting houses with secondary suites to be built of combustible construction, require a 30-minute fire separation between two units, possess interconnected hard-wired smoke alarms and permit either combined or independent HVAC systems.

Phase-in date: July 1, 2017

  1. Radon Mitigation: This is an expansion of the existing OBC requirement which currently includes mandatory radon mitigation in only three Ontario areas – the City of Elliot Lake, the Township of Faraday and the Geographic Township of Hyman – and certainly not the GTHA. This change would align with the model National Building Code (mNBC) and require radon mitigation in the construction of all new houses and large buildings (condos). Supplementary Standard SB-9 outlines potential approaches to mitigating radon ingress, namely sub-slab depressurization, utilization of high-strength concrete and impermeable vapour barriers.

Phase-in date: January 2019

Estimated cost increase per low-rise home: $1,000+

  1. Stairs and Guards:
    This change moves to harmonize with the mNBC and would mandate longer stair runs with deeper tread depth (increase from 210 mm to 255 mm) and limit the “climbability” of guards. Therefore, a typical house staircase would lengthen, thus impacting usable interior space. The reasoning behind this change is that a deeper tread depth should provide better foot placement for stability, resulting in fewer falls.

Phase-in date: January 2019



1. Supplementary Standard SB-10 (Energy Efficiency Requirements): SB-10 outlines compliance paths that represent a 13% improvement over the current energy-efficiency level for buildings. The compliance paths include improvements to insulation, mechanical heating/cooling devices, more stringent requirements for greenhouse gas emissions and peak electric loads as well as encouragement for the use of renewable technologies to reduce the carbon footprint of new buildings. The compliance paths are based on revised energy codes, namely ASHRAE 90.1, ASHRAE 189.1 or the National Energy Code of Canada (NECB).

Phase-in date: Jan. 1, 2017

  1. Structural Integrity – Seismic Considerations: This is another change that is moving to harmonize with the mNBC, largely impacting Part 4 (Structural Design) of the OBC. The proposed changes are intended to introduce minimum levels of lateral strength and toughness in buildings and to remove the trigger exempting the application of seismic design. While previous versions of the OBC did not require seismic design in low zones, it was never meant to imply that earthquakes could not exist in these regions. The driving cause of this change stems from recent data that indicates that no region is entirely free from earthquake hazards and earthquakes can occur in low seismic regions.

Phase-in date: January 2019

Estimated cost increase: 0.2% of the total building cost (source: Ministry of Municipal Affairs [MMA])

  1. Design Load Requirements:
    This change builds upon the previous one; buildings will have revised design requirements with respect to wind loads, load combinations and loads due to snow and rain, harmonizing with the mNBC.

Phase-in date: January 2019

Estimated cost increase: 0.1% of the total building cost (source: MMA)

4. Sound Proofing: This OBC change builds on existing requirements and will harmonize with the mNBC. Changes include considerations to address “flanking noise,” which is noise that travels from one unit to another through gaps or discontinuities in walls, floors and other structural elements. Increased soundproofing requirements will be mandated between dwelling units in multi-unit residential buildings to cut down on noise transmission from other units and common areas. This change will also affect certain attached low-rise housing units, such as townhouses.

Phase-in date: January 2019
That’s just a quick overview. There are more than 400 other changes that we have not touched upon here. In analyzing the cost implications, each change may appear to have a relatively minor incremental cost, but when considering the aggregate costs, these changes can add up quickly.

For more information on these changes, including an overview document and an index of the proposed OBC changes, click on this link.


Courtesy of Paul De Berardis is RESCON’s director of innovation and building science as well as chair of the Building Innovation Group. Email