Building Types | Triplex
Triplex: Permitted Everywhere, Built Almost Nowhere
Bill 44 made the triplex legal on essentially every former single-family lot in BC. Builders have mostly chosen four units instead. The reason is not the legislation — it is the floor-plate geometry of the standard 33-foot lot.
Key Takeaways
- ✓Triplex is permitted on every SSMUH lot but built rarely.
- ✓Three units rarely fit Vancouver's market either as family homes or as rental studios.
- ✓Triplex makes sense on wider lots, on retained-character conversions, and for multi-generational use.
- ✓Stacked triplexes typically trigger BC Building Code Part 3 (multi-unit residential).
Three Common Configurations
Stacked triplex (three storeys)
One unit per floor, one shared stair. Common in Montreal walk-ups and increasingly in Vancouver SSMUH applications. Each unit gets the full footprint of the building per floor.
Two-up, one-down
Two upper units stacked, one ground-level unit at grade. Often the result of converting a single-family house with an existing basement suite into a stratified triplex.
Front + rear duplex
A front-facing duplex with a rear unit accessed off the lane. Three doors, three independent units. Bridges the duplex and fourplex shape.
Why The Math Is Awkward
A 4,000 sq ft Vancouver lot at 0.7 FSR yields 2,800 sq ft of building. Divide by three units and each one comes in around 930 sq ft. That unit size sits in the gap between BC's two strongest demand pools: families want at least 1,200 sq ft and a real second bedroom, while the rental and pied-a-terre market wants 500–700 sq ft at lower price points. The triplex unit overshoots the rental market and undershoots the family market.
Push to four units at the same FSR and each unit drops to 700 sq ft — squarely inside the rental and entry-level strata market. Push to two units (duplex) and each becomes 1,400 sq ft — back in the family market. Three units sits between two equilibrium points.
When Triplex Is the Right Call
Triplex works on lots between 50 and 70 feet wide where the floor plate naturally divides into three rather than four. It works on lots with a retained character house where one unit is the original heritage shell. It works for multi-generational families that want one unit each for grandparents, parents, and adult children. It works on corner lots where two of the three units can have street frontage on different streets.
It does not work on standard 33-foot mid-block lots where the FSR is the binding constraint. On those lots, a fourplex almost always returns better economics.
Code Path Considerations
A stacked triplex with one common stair pulls the project into BC Building Code Part 3. That changes fire separation, sprinkler, exit-sign, and accessibility requirements relative to a Part 9 small-residential build. A triplex configured as front + rear duplex with three independent egress paths can sometimes stay under Part 9. The choice has cost implications.
Confirm the code path with a building official or BC-registered architect before relying on a Part 9 design for a three-unit building. Mistakes are expensive at the framing stage.
Best For
- ✓ Wide lots where four units force an awkward division.
- ✓ Retained-character conversions where the original house anchors one of the three units.
- ✓ Multi-generational use cases with three distinct family groups.
Usually Fails When
- ✕ Standard 33-foot lots with no special constraints — fourplex usually wins.
- ✕ Markets that want either tiny rental units or family homes, not the middle.
- ✕ Owners assuming Part 9 code applies to all three-unit configurations.
What To Verify Before Spending Money
- → Whether your lot geometry actually favours three units over four.
- → The BC Building Code path with a registered design professional before applying.
- → The strata or rental tenure that fits three larger units in your local market.
Frequently Asked Questions
Why are triplexes uncommon in built BC SSMUH?
When does a triplex make sense?
Are triplexes still legal everywhere a fourplex is?
Does a triplex trigger BC Building Code Part 3?
What is the financing pattern for a triplex?
Official Sources Referenced
Screen Your Lot for Missing Middle
Enter any BC address to see what Bill 44 SSMUH unit count, lot coverage, and FSR your parcel actually qualifies for.