Fire Separation code can be the wall that separates an owner from the reality of legally opening an income-producing second suite. Going with the spirit that beside every obstacle there exists a path forward, we’ll break down the walls of mystery in the Code and build them back up with solutions.

Two-Suite Residential Building Code Requirements

In a 2-suite residential building, any wall that separates one building compartment from the other is a Fire Separation Wall. This includes any walls on the same storey which are shared between both suites where one side is part of the main suite and the other side is part of the secondary suite. Stairwells count as living space, so in the common scenario of a lower level entry stairway to an upper suite that runs through the lower suite, the stairwell walls are a Fire Separation. Walls between living space and enclosed garages are also Fire Separations; exterior walls that face in to an open carport are not. Walls which face on to the exterior of the building are not Fire Separation walls, though there are cases where a continuous wall section runs from being exterior in to becoming an interior separation wall, so special care must be taken to make sure that the wall design meets both exterior environmental separation needs and is also built in accordance with Fire Code. A related tricky scenario when building additions is where a once exterior wall becomes an interior Fire Separation Wall and new Code sections all of a sudden apply. Mix all this in with the fact that Codes have changed a lot over time, and the lights might look a little dimmer overtop the challenge of renovating an existing structure and making a legal Fire Separation suite.

Owners and builders have many options when building a Fire Separation for a secondary suite, a good thing for the experienced and educated practitioners who can use the multitude of solutions to fit their budget and aesthetic tastes while achieving safety and protection. With so many options, it might seem hard to pin down and choose the right approach. When doing renovations and additions to create a second suite, existing structural design details must be incorporated in to the creation of a Fire Separation, making it difficult if those details do not fit in to what is prescribed in the Code. That’s a problem less encountered in new construction, however, with many different products on the market and the needs and desires of owners, such as soundproofing and energy efficiency, even in new construction the design may not fit what’s spelled out in the Code. Let’s explore the three methodologies of meeting Code when designing and building a Fire Separation Wall.

Step Required to Meet Fire Code

1) Prescribed construction assembly. There are over 260 different Fire Resistance wall designs listed in Table A-9.10.3.1.A in the BC Building Code. That’s a lot of options, starting with the simple and most common designs in wood-framed construction which are used in the majority of residential designs in BC. Many houses that are being converted for a secondary suite have wall details that match a design in Table A-9.10.3.1. If one can be so lucky, it’s still up to the owner, builder or engineer to prove to the code official that this is the case.

2) Engineering Evaluation based on testing to CAN/ULC S101. There are many additional acceptable construction details and products in the marketplace that are not listed directly in the Code, not a show stopper though, as the Code provides guidance as to how approved laboratories can perform tests that demonstrate compliance of the fire-resistance rating. Appendix D-1.1.5 addresses this and directs the user to lists of rated products and assemblies by laboratories such as Underwriters Laboratories of Canada (ULC) and Intertek Testing Services (ITS). Another laboratory source in BC is QAI Laboratories (QAI) located in Vancouver. Earlier we discussed cases where a structural addition on to an exterior wall converts the once exterior wall in to an interior wall, making it a Fire Separation. If the exterior wall was designed with specialty products for the exterior, such as waterproofing and insulations, it would have to be proven that a sample wall construction with those products was tested and met the requisite Fire Resistance rating. Take an example of an exterior wall constructed with Insulated Concrete Forms, which is not one of the prescribed wall details in Table A-9.10.3.1.A, being converted in to an interior suite-separation wall by an add-on to the exterior side of the building. The building official would ask to see that a laboratory has tested and listed such a wall assembly for interior Fire Separation standards. See the example of a Logix ICF laboratory listing design, which would qualify for such a condition.

3) Component Additive Method. Appendix D-2.3 has list tables of materials of known fire-resistance minutes (e.g. 5/8” Type X gypsum board is worth 40 minutes). One can design a Fire Separation by adding each component’s individual contribution to the sum total by stacking layers until the minutes add up to the needed rating, up to 90 minutes. This method is convenient in the renovations scenario if an existing wall doesn’t meet the design criteria though it contains materials that are listed in these tables such as 2×4 framing lumber. Spaced at 16” o/c, framing lumber has a contribution rating of 20 minutes, which can be left in place and then built on top of with other materials such as gypsum board to eventually make it qualify as a Fire Separation, saving the owner from having to start over with entirely new design and materials.

Once the base wall assembly details make it through the criteria for being a Fire Separation, any through penetrations and openings, such as those for electrical, plumbing, and doorways, must be installed in such a way that the Fire Resistance of the whole assembly is not comprised. We’ll dive in to that subject next time in the Alair Homes Victoria blog series on Fire Code for secondary suites.

Chris Bowness, P.Eng., owner and general manager of Alair Homes Victoria, previously worked in the field of Fire Safety laboratory testing for 12 years, and has tested and evaluated thousands of fire-rated construction products to the methods described in the BC Building Code.