Divide & Conquer

By Signe Langford

The opportunities and obstacles of multiplex conversions

When the Government of Ontario introduced Bill 185, it was designed to quicken government processes and encourage the building of at least 1.5 million homes by 2031. But in housing math, you can also get addition by division—as in creating more than one residential unit within a home. 

“To support the implementation of Additional Residential Units (ARUs), such as basement suites, our government brought forward Bill 185, the Cutting Red Tape to Build More Homes Act, 2024, which allows Planning Act changes that enhance regulation-making authority related to ARUs,” noted Bianca Meta, Press Secretary, Office of the Minister of Municipal Affairs and Housing. “This will allow the government to remove municipal zoning by-law barriers that may be limiting the development of ARUs.” 

Theoretically anyway. But obstacles remain. And while the process of adding one or more self-contained units to an existing structure may be faster and less expensive than building from the ground up, there are challenges, pitfalls, hidden costs and municipal hoops aplenty. We asked four builders to share their stories. 

Sensitive Design

In Toronto, Eurodale Developments is in the process of converting an existing four-plex into a 10-plex. Located directly across from iconic Casa Loma, Development Manager Brendan Charters describes how “architecturally sensitive” Eurodale is being with this retrofit. “We restricted the third floor from the existing roof ridge to the back. A small dormer in the existing roof is the only change you see from the street,” he notes. “All the windows are being replaced to match the existing fenestration and mullions, and we are not making the building any taller than the existing surrounding buildings. Now that’s sensitive! We only had one objection from a neighbour who was afraid of parking challenges. The rest of the neighbours were supportive and the committee members that approved it were very complimentary of the design and sensitivity of the proposal.”

Public sector support can be particularly dicey for such projects. “The multiplex housing file is always a bit convoluted,” Charters says. “The City is quick to advise how desperately they want new housing, and then put rules and practices into place that impede that end goal. And reasonable building examiners and field inspectors can make conversions run smoothly, or they can make it extremely challenging.”

Another frustration Charters expresses is a lack of communication between departments within the City. “Planning staff write a supportive report for the application, and then City legal, directed by local councillors, opposes the application to TLAB (Toronto Local Appeal Body). The Province mandated three units be permitted as of right, but many smaller bedroom municipalities pretend as if it’s not the case and is not permissible under their zoning bylaws, which is not a requirement for the permission!” 

Provincial mandates trump municipal bylaws, but that means time and money spent on a fight, a fight not everyone can afford, leaving some towns lagging behind their required housing numbers. 

How does Eurodale approach this inconsistency and pushback? “We remain active and link arms with other people in our industry and organizations—such as Expanding Housing Options in Neighbourhoods—with the City of Toronto to further the cause of gentle densification and missing-middle housing. We work at getting John Q. Public used to and accepting of this sort of building.”

Among the many ways the multiplex conversion process differs from building a new single-family home is that “if the builder is creating three units or three storeys or more, designers require a small-buildings BCIN (Building Code Identification Number), not just a house BCIN, as is most common,” Charters explains.

Once you’re physically into the home, requirements could include everything from separate HVAC systems to electrical upgrades. “In a new build—whether above, below or beside—or a new addition to an existing residence whereby you are creating a new suite, you have to achieve an STC (Sound Transmission Class) rating of 51 or higher for sound attenuation between suites,” Charters explains. “But when converting an existing building with more than one suite there’s no STC requirement. And you must achieve a 30-minute FRR (Fire Resistance Rating) versus 45 minutes in a new build. For this specific project, where there were already four existing suites, so we won’t be making any STC or FRR changes there, as the existing old lathe and plaster provide adequate FRR. And no STC rating is required under Part 11 of the OBC, as they are considered ‘existing’ and, therefore, acceptable assemblies for fire and sound. But for the new units, including the basement and third floor, we will be creating assemblies with a 45-minute FRR and an STC rating of at least 51.

“Another consideration is exterior open-air exits from lower-level units, which may require very costly fire shutter applications to openings above them,” Charters cites. 

Hydro requirements are front of mind, given the growing numbers of electric vehicles and a focus on reducing carbon. “But our grid infrastructure is not always what we need it to be for a particular site, and the monopoly system we have for utility providers can make this servicing challenging and costly,” Charters notes. “City sewer and water infrastructure can handle this type of gentle intensification, but the buildings’ services themselves will often need upgrading. The water supply service needs to be at least one inch, and the amperage from Hydro needs to be 100 amps for electricity draw for a new unit. Up until now, we’ve been able to avoid major upgrades by running gas to furnaces, dryers and stoves, but with the carbon reduction targets locally and nationally, we are staring down major electrification of homes, and that will mean major—and expensive—power upgrades from local utility providers.”

In 12 years of consulting with clients who want to add a self-contained unit or a second standalone unit to their property, Charters has seen his share of mistakes, miscalculations and misconceptions. “The top misconception is that the cost to build a multiplex is going to be the same as a single-family dwelling because they are the same shape, size and built form. But the number of additional kitchens and bathrooms alone really skews those cost-per-square-foot numbers, let alone the fire and sound construction work that must be undertaken,” Charters says. “The other misconception is that the City and the neighbours are going to be supportive of this new housing typology. If it’s a rental, the stigma and fear of the unknown by the local constituents quickly shows its face.” 

Still, Charters is fielding a growing number of calls to add additional residential units—and he understands why. “This is a great opportunity for young people to pool their resources and develop a low-rise housing alternative to the high-rise condo. And it’s perfect transition housing. For youth, it can be a transition out of their parents’ homes or from a shoebox condo into this low-rise product type. For an empty-nester or retiree, it allows them to remain on their property while adding some income and even potentially some mobility or maintenance help. And it provides the potential for multigenerational living, but with greater autonomy by having individual suites with locking doors. The options and opportunities abound. It just takes time for people to see the success of projects built before they are totally comfortable doing it themselves.” 

Upscale Offerings

In Ottawa, Amsted Design Build’s Director of Construction Lindsay Haley has also seen a growing interest in multi-unit conversions. “In some cases, it’s to provide private or semi-private multi-generational living, and for others it’s to provide supplemental income,” Haley says.

“In Maitland, Ontario, we were tasked with converting an 1820s stone carriage house into two upscale rental villas. As you can imagine, this came with a host of challenges. Even though there are government grants to encourage multi-unit dwellings, every city has its own considerations. In this case, the township would not allow this type of renovation, so we had to work closely with the planning department to acquire the appropriate zoning requirements. Further, adding a garage required a variance, which meant engaging the neighbours for their approval. There’s also the structural and systems requirements of dividing a single building envelope into two separate spaces. Given the age of the building, we were working with limited vertical height allowances and 24-inch-thick stone walls, which we could not impact. 

“To maintain the heritage of the building while creating height for the second floor, we added dormers and a rear extension, fabricating a ridge beam on-site for structural support,” Haley explains. “Given that we couldn’t change the outer structure, we had to maximize every available inch inside. This also came with its own challenges, given each unit required individual HVAC systems, plumbing and water supplies. Finally, we also had to adequately soundproof between units for privacy and ensure the necessary fire protection, while maintaining the open-beam design.

“One of the biggest challenges when creating attached multi-unit dwellings is the need for separation,” says Haley. “Fire is perhaps the biggest consideration, as it presents the greatest risk to the occupants. It demands things such as thicker drywall and a different application, fire-rated doors, higher standards for insulation values and secure openings. There must be a complete separation between units so that if a fire starts in one, it has the very best chance of staying contained. When you’re working within an existing structure, you can imagine the kind of intricate planning and execution that takes.”

For fire protection, Amsted used a double layer of 5/8” Type X drywall, which offers 45-minute to one-hour fire rating protection per layer. Amsted also used Rockwool’s Safe‘n’Sound stone wool insulation in interior partitions of residential wood, and steel stud construction where superior fire resistance and acoustical performance were required. The Safe’n’Sound product also offers strong acoustical dampening properties, while acoustical wall panels offer further noise reduction.  

“These projects,” says Haley, “are a delicate dance between professionals—designers, engineers, surveyors, trade partners, the construction team, inspectors and more. And that requires collaboration from design through to construction.” Part of our process involves bringing the trades on-site prior to the job starting to bring their expertise to design. And then, when things inevitably change throughout the job, you want your designer to be able to come back in and support any changes needed throughout construction.

Haley agrees with Charters that the most common misstep with this sort of project is underestimating the cost, which is driven up by creating that complete separation between units. While aspects like fire separation are non-negotiables, there are a host of other decisions that homeowners and builders must make surrounding the home’s systems that require a careful weighing of options. Some may impact individual unit comfort. For instance, providing a furnace for each floor of a three-storey triplex ensures year-round comfort controlled by each occupant. Having separate hydro meters helps monitor costs and provide accurate per-unit billing for tenants. Of course, the cost for two or three of anything will add to the upfront investment, and that can be problematic if it occurs in the midst of a project. 

Going to Great Heights

Charles Wah, president of Hamilton-based Gateway Group, is also familiar with unanticipated costs. But sometimes it’s the municipality that unexpectedly digs deep into your pockets. Wah originally planned on converting a grand century home in Hamilton into four units last year, but after the City of Hamilton decided not to waive the $90,000 in development charges and cash-in-lieu of parkland dedication for the fourth unit, Wah revised the plan to three legal units. 

“The City of Toronto waives DCs and cash-in-lieu of parkland dedication for up to four units, whereas the City of Hamilton only waives them for up to three,” Wah notes. “Although Hamilton permits four units publicly, the development charges make it impractical. It’s also an expense most homeowners are not aware of when they enter into such projects.”

As always, the devil is in the details, Wah explains. “A house in the Ontario Building Code is defined as a dwelling with up to two units. But the requirements for three units and above become significantly more stringent, which makes it more complicated to meet. For example, the required basement ceiling height is 6’11” for new homes versus 6’5” for older homes. And since dwellings containing three units or more are considered a ‘small building’ and not a ‘house,’ any basement apartment needs to be at least 6’11” in height. Fortunately, in the new code coming into effect in 2025, it appears they will get rid of the 6’11” height requirement for basements in ‘small buildings.’” 

Egress requirements are a consistent challenge with multiplex conversions, including Wah’s Hamilton project, as ‘small buildings’ require a second means of egress if the entrances are shared. “In most places in the world, only one point of egress is required,” Wah notes.  

Another speed bump Wah encountered during the seven-and-a-half-month project was having to upgrade the municipal water line to one inch due to the number of plumbing fixture units being installed, which is what the town uses to determine the estimated water demand. The electricity had to be upgraded to 200 amps, although that was expected. 

Rising Costs

Speaking of speed bumps, Novacon Construction President and Construction Manager Pavel Bigas had embarked on a Bloor West conversion just as Covid hit. When the usual challenges inherent in reformatting a single-family home into a multiunit dwelling were combined with the pandemic-related logistics and skyrocketing material prices, this quickly became the most challenging project in Bigas’s two-decade-long career.  

“The owner bought the property as an investment and had been working with an architect for approximately one and a half years to get through all the red tape of zoning, permits and design issues with gutting and adding on to a home that was literally 1.5 inches away from the neighbour’s wall,” Bigas relates. “The initial budget he was given by his architect was approximately $400,000 to $500,000. When he came to us and other contractors, we were all in the $800,000-$900,000 range, which was a huge shock to the client. 

“With all of the new laws coming through allowing multiplex homes, some of the biggest issues came from the neighbours, as the old NIMBY attitude is quite common, especially in our higher-end neighbourhoods where home values are in the $2-million-plus range,” says Bigas. 

“Beyond the typical back-and-forth delays of seeking approvals with the building department, a particular challenge was that after removing the existing roof to add the third floor, we discovered the neighbour’s previous roofer had attached their roof to ours, making that process quite difficult and adding further costs and time.” The drain on time is always hard to avoid in such projects, Bigas observes. “Every point of penetration must be fireproofed to be OBC-compliant. Even simple things like pot lights require a special fire-rated housing for each unit, which in some cases costs as much as the actual pot light installation itself. All bulkheads had to be well-thought-out to meet these requirements, where typically they are almost afterthoughts. We utilized hydronic in-floor heating in this unit since we were already underpinning and lowering the basement. We wired each unit with a separate panel that runs from one main service line out to the street. It does cost more but keeps each unit separate. If a fuse blows in one suite, we are not bothering the other tenants.”

It’s a key to success in multiplex conversions: When it comes to splitting up a single structure, the better you keep them apart, the more the whole building grows in harmony. 

It’s all part of that ‘addition by division’ math. 

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