Triplex Design Guide for BC
Complete guide to building a triplex in BC — standardized designs, lot requirements, construction costs, and where triplexes are permitted.
Key Takeaways
- ✓ Triplexes provide 3 units on a single lot, offering a strong balance of density and neighbourhood fit.
- ✓ BC catalogue Triplex 1 is the standardized triplex design, with flexible unit mix configurations.
- ✓ Typical lot requirements are 40 ft frontage and 4,800 sq ft area.
- ✓ Total construction cost ranges from $1.0M to $1.7M depending on size and finishes.
- ✓ Triplexes remain Part 9 buildings under BC Building Code, keeping construction straightforward.
What Is a Triplex Under BC Building Code?
A triplex is a residential building containing exactly three dwelling units on a single lot. Under the BC Building Code, triplexes are classified as Part 9 residential buildings (up to 3 storeys, 600 m² per unit), allowing prescriptive construction methods similar to single-family and duplex construction.
The SSMUH legislation requires municipalities with populations over 5,000 to permit 3 to 4 units on lots previously zoned for single-family housing, making triplexes a viable option in most Metro Vancouver cities. Triplexes occupy a sweet spot between the simplicity of a duplex and the density of a fourplex.
Which BC Catalogue Designs Apply?
The BC standardized designs catalogue includes one triplex-specific concept. Using this pre-approved design can accelerate permitting and reduce professional fees.
Triplex
Three units arranged across 2-3 storeys with a combination of stacked and side-by-side configurations. The design allows flexible unit mixes -- from three equal-sized 2-bedroom units to a larger ground-floor unit with two smaller upper units. Each unit has an independent entrance and private outdoor space.
Lot Requirements
Triplexes require slightly larger lots than duplexes to accommodate the third unit and additional parking and outdoor space.
| Specification | Triplex 1 (Triplex) |
|---|---|
| Minimum Frontage | 40 ft |
| Minimum Depth | 100 ft |
| Minimum Lot Area | 4,800 sq ft |
| Typical Zones | R1, RS-1, RS-2 (larger lots) |
| Max Height | 10.7 m (35 ft) |
| Max FSR | 0.85 - 1.0 |
| Units | 3 |
Triplex 1 — Unit Stacking Configuration
UNIT 3 — Upper
1-2 Bedroom · ~650 sq ft
UNIT 2 — Middle
2 Bedroom · ~750 sq ft
UNIT 1 — Ground (Accessible)
2-3 Bedroom · ~850 sq ft
Illustrative stacking — actual unit sizes and layouts vary
Design Considerations
Accessibility
At least one unit must have a barrier-free path from the street and an adaptable principal floor. In practice, the ground-floor unit is designed as the accessible unit with level entry, wider corridors, and reinforced walls in wet areas. Upper units may be reached by stairs but should have adaptable features where feasible.
Fire Separation
All assemblies separating units require a minimum 1-hour fire-resistance rating. With three units, the number of fire-rated assemblies increases -- particularly in mixed stacked/side-by-side configurations where both vertical and horizontal separations are needed. Each unit must have independent egress.
Sound Transmission
Inter-unit assemblies must meet STC 55 (airborne sound) and IIC 55 (impact sound for floor/ceiling assemblies). With three units sharing walls and floors, careful attention to acoustic detailing at junctions is critical. Resilient channels and acoustic sealant at all penetrations are essential.
Privacy
Triplex design should create distinct "address" identity for each unit with separated entrances. Window placement should be offset to avoid direct sight-lines between units. Private outdoor spaces -- patios, decks, or balconies -- help each unit feel like an individual home.
Where Are Triplexes Permitted in BC?
Triplexes are permitted in most Metro Vancouver municipalities on lots that meet minimum size requirements. Some cities may require proximity to transit for 3+ unit developments.
| Notes | |||
|---|---|---|---|
| Vancouver | 6 | Adopted | Permitted on lots 40 ft+ frontage in R1-1 zones |
| Burnaby | 4 | Adopted | Larger lots in R1 zones; min 4,800 sq ft |
| Surrey | 4 | Adopted | All single-family zones meeting lot size |
| Coquitlam | 4 | Adopted | RS zones; transit proximity may ease requirements |
| New Westminster | 4 | Adopted | Most residential zones; lot size dependent |
| North Vancouver (City) | 4 | Adopted | RS zones with adequate lot size |
| Port Moody | 4 | Adopted | Select zones; lot size and frontage dependent |
| Port Coquitlam | 4 | Adopted | RS-1 zones; transit proximity preferred |
| Richmond | 4 | Adopted | Single-family zones; flood construction level applies |
| White Rock | 4 | Adopted | Select residential zones |
Cost Breakdown
Triplexes benefit from economies of scale compared to duplexes -- shared systems, a single foundation, and one roof covering three units.
Hard Costs
$400 - $480
per sq ft
Soft Costs
$100K - $140K
permits, design, fees
Total Project Cost
$1.0M - $1.7M
for all three units combined
Hard costs include foundation, framing, mechanical, electrical, plumbing, and finishes. Soft costs include architectural design, engineering, permits, surveys, legal, and project management.
Energy Requirements
All new triplexes must comply with BC Energy Step Code, typically Step 3 or higher depending on the municipality. Triplexes have excellent energy efficiency potential -- with three units sharing walls, heat loss is significantly reduced compared to detached homes. Key requirements include high-performance building envelope, heat recovery ventilation, and airtightness testing. The additional unit helps spread the cost of energy upgrades across more rentable area.
Run the Numbers for Your Property
Use the VanPlex proforma calculator to model triplex development scenarios on your specific lot -- including construction costs, financing, rental revenue, and return on equity.
Try the Proforma CalculatorFrequently Asked Questions
What unit mix options are available for a triplex?
Common configurations include three 2-bedroom units (ideal for families), two 2-bedrooms with one 1-bedroom (maximizes flexibility), or one 3-bedroom with two 1-bedrooms (great for owner-occupied with rental income). The BC Triplex 1 design accommodates all of these layouts.
What are the parking requirements for a triplex?
Under SSMUH legislation, municipalities cannot require more than one parking space per unit (three total). Properties within 400 m of frequent transit may have reduced or zero parking requirements. Tandem parking configurations are commonly used to fit spaces efficiently on the lot.
What fire separation is required between triplex units?
All assemblies separating dwelling units require a minimum 1-hour fire-resistance rating. This applies to both party walls and floor/ceiling assemblies in stacked configurations. Each unit must have independent egress to the exterior and interconnected smoke alarms within each unit.
Can I build a triplex on any single-family lot?
Not every lot qualifies. Triplexes typically require at least 40 ft of frontage and 4,800 sq ft of lot area. Lots in municipalities with populations over 5,000 must be zoned to allow 3-4 units under SSMUH, but the specific lot must still meet minimum size requirements set by the local bylaw.
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