What Are The Top 3 Things People Forget When Designing A Multiplex?

Daniel Clarke
May 29
7 min read

Your SSMUH project will suffer if you don't address several aspects of designing and building that are unique to a multiplex.

If you take into account the considerations I explain below, you will substantially de-risk your project and be more confident in avoiding traps as the project unfolds.

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Many people approach multiplex development with what seems like a promising assessment, yet they often overlook or underestimate critical factors unique to multifamily buildings—factors that can erode profit margins or undermine the project to the point that it no longer delivers a worthwhile return to families or to investors.

Developing a SSMUH requires a large investment and can be a tragic gamble. If you have determined that creating a multiplex will provide adequate return on investment as a sale or through rental revenue, or if your family has determined that it can afford the development and construction costs of a multifamily home, the calculation almost certainly shows a very tight margin. There is essentially no room for error or big surprises. I'm going to explain the reasons behind some of these big surprises.

#1 A Multiplex Is Not Just A Big House

The building code requirements for a house and for a duplex are significantly and substantially more relaxed than those of a building that contains three or more dwelling units. If your architect or designer doesn't factor these into the design, the city building permit review staff will flag them - or they will be identified by the building inspector during the construction phase.

Exemptions

The design of single-family houses and duplexes rely on exemptions that don't apply to buildings with 3 or more dwelling units. The general topics of fire protection, exiting, accessibility, acoustic separation, HVAC specifications, and specific structural load calculations are introduced for a three-dwelling unit building and may not be familiar to house designers or to some architects who specialize in single-family and duplex architecture.

Adaptability

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Adaptable dwelling units are residential suites that are designed with certain sizing and features that enable simple renovations to make the unit suitable for people with limited mobility or other impairments. The new building code - applicable everywhere except in Vancouver - states the requirements for an adaptable dwelling unit and requires a certain portion of the residences to be adaptable dwelling units. A city may have a bylaw that requires a higher portion of new units to be adaptable. Since an adaptable dwelling unit generally takes up more space, the profitability of a project intended for sale or rental revenue may be reduced or destroyed.

#2 Are You Even Eligible

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At first glance, the messaging from the provincial government - often largely repeated by the city governments - is tantalizing: "ALL SINGLE-FAMILY ZONES CAN HAVE MULTIPLEXES" or something similar. For the most part, that's more or less true. Many interested property owners also understand that there are exceptions. To avoid wasting time and possibly wasting money on pointless design exercises or even a feasibility study, you need to ensure that your lot is eligible for a SSMUH development. If it is you must then quickly understand generally what type of multiplex you are permitted to build.

Zoning Basics

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It seems that everyone or virtually everyone understands zoning, but it's worth elaborating on the topic. The zoning for your lot must be one in which SSMUH is permitted. Some cities have developed or are adopting variations on single-family zoning, and some of those zones don't permit multiplexes.

The restriction may stem from infrastructure limitations (water supply, sewer capacity), from physical factors (geological limitations, unsuitable slopes), or from heritage concerns (e.g. Old Town villages and the like) where higher density, new homes would disrupt the intrinsic and unique appeal of the single-family developments there (for example a cluster of restored listed heritage buildings).

Heritage Controls Are Strict

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While not strictly a zoning issue, the form and character aspect of your proposed building is also a point to consider. Even if the city allows you to build a multiplex, you may not be allowed to build the type of multiplex you envisioned. In most jurisdictions, the Planning department still must review the proposal to ensure that the building fits with the neighbourhood or with the vision for what the neighbourhood will become. In an area where there is a lot of heritage or character construction, the only successful proposal may need to reflect that aesthetic.

I've also heard from house owners who hoped to reconfigure the house and create an addition, to create a multiplex. In Vancouver, a multiplex is not an option for a renovation. It's also not an option for a heritage building. The Multiple Family Conversion Dwelling, however, is a similar option that could apply.

Minima and Maxima

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The provincial legislation excludes lots that are larger than roughly 40,000 sq.ft..I was approached by an owner of a large lot at the edge of the city. While he had a logical, modified proposal for the city to develop small-scale multi-unit housing suitable for that site, he was told flatly, "No.".

Your lot may instead be not large enough - or it may be too narrow. Another owner with whom I spoke owned a lot that was 1' narrower than the minimum required for a multiplex. Again, the response from the city was an unflinching, "No.".

Access To Your Lot

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The city is typically concerned with the access to the property. The local fire department may be agreeable to a multiplex only if there is a rear lane, such as in Vancouver. Under Vancouver's rules, a lot without rear vehicular access are not eligible. In most cities, the Planning staff may also have restrictions on or requirements for vehicle access from a main street, so that traffic is not endangered.

#3 Zoning Bylaws and Building Codes Are Not The Only Regulations

Some drafting firms may be more familiar with the building code but less aware of municipal Planning department regulations outside of the city's Zoning Bylaw.

City Master Planning Underpinnings

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The "master plan" document upon which all zoning is based is almost always called an Official Community Plan (OCP). Vancouver however had a mosaic of regulations that comprised the Vancouver Plan - an umbrella campaign that stitched together the other rules to achieve common goals. The Vancouver Plan will soon be transformed into an Official Development Plan (ODP). Regardless of the master plan's format, there exist various rules.

Neighbourhoods Set The Tone

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Neighbourhood Plans strive to distinguish or maintain the distinction of different parts of the city beyond the distinction that a zoning type provides. The associated character of a neighbourhood plan may determine to some degree what form or style the city wants a multiplex to exhibit. In a similar fashion, a neighbourhood with a strong heritage character in many of its buildings may not have a neighbourhood plan, but the Development Permit application for your multiplex project may elicit City Planner review comments suggesting styling that complements the existing heritage architecture.

In some cities, the regulations that are adopted may lead you to refer to the dwelling unit density - the number of units that are permitted to be built in a given area. In a similar fashion, the city may mandate certain parts of the city to be rental-only. Being limited to creating only a rental building may render a multiplex project non-viable.

Regardless of the extent and structure of these Planning-related regulations, the common aspect is their subjective nature and corresponding subjective review for compliance for approval by the Planning department.

What Is Your Plan Now?

For the last two-thirds of my 25 years in the architectural profession, I've worked largely on multifamily and mixed-use buildings -- projects for which I needed to develop a solid and broad understanding of a variety of city regulations both technical and aesthetic.

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The underlying characteristic of my SAPPHR Strategy(tm) - the process I developed for designing projects - is a pragmatic, investigative, and detailed approach. Working away without first understanding all the relevant constraints and other parameters wastes everyone's time and more importantly leads to critical compromises.

Maybe this is your first construction project, or maybe it's your twentieth; a fruitful outcome whether financial or not is why you're investing the effort and money. A thorough process that confirms all the city's requirements helps to ensure smooth sailing and an outcome that matches your initial objective.

Alternatively, the "figure it out as you go" approach usually ends up somewhere you didn't plan to go. The building falls short of what was intended, and the whole exercise brings into question the decision to have gone ahead with it at all.

If you or an acquaintance is interested in developing a multiplex, the initial research phase is the best time to investigate all the restrictions - not after you've drawn the site plans.

The SAPPHR™ Strategy is a framework and methodical progression through pre-design and design to delete assumptions, optimize design, and unnecessary construction work. You can download a copy of the SAPPHR™ Strategy client manual at the link below.

>>> DOWNLOAD CLIENT MANUAL <<<

For those poised to take the first step to better buildings, I offer a free, 30-minute consultation - the Diagnostic Session. You're not just investing in a property; you're contributing to a sustainable future, crafting a legacy for either your family or for your brand.

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DISCLAIMER:

The information included in this article is to an extent generic and intended for educational and informational purposes only; it does not constitute legal or professional advice. Thorough efforts are made to ensure the accuracy of the article, but having read this article, you must understand and agree that Daniel Clarke Architect Inc. disclaims any legal liability for actions that may arise from reliance on the information provided in this article. I am an architect in BC, but readers are recommended to consult with their own architect on their specific situations before making any decisions or exercising judgement base on information in the article.