Fourplex vs Sixplex in BC: When More Density Costs More Than It Earns

More doors reduce land cost per unit—not necessarily total project cost

Land is a major expense in many Lower Mainland developments. Dividing it across more homes can make the project look more efficient.

In a hypothetical example, a $2.4 million site represents $600,000 of land cost per unit for four homes, or $400,000 for six. The land still costs $2.4 million. That calculation says nothing about the additional construction, consultant fees, servicing or financing needed to deliver the extra homes.

More units also do not guarantee more saleable floor area: permitted density, setbacks, height, lot coverage and circulation all matter. Compare the achievable layouts and supported sale prices or rents, rather than multiplying one unit’s value by six.

What changes when you go past four units?

The architect requirement needs early attention

BC’s Architects Regulation includes a residential building with five or more dwelling units within the reserved practice of architecture. Other triggers include building area over 600 square metres and four or more storeys, along with specified uses and circumstances.

A fourplex may fall outside those requirements, but four units alone do not establish an exemption. Have a qualified professional confirm the actual building configuration, particularly where units are spread across separate buildings.

For a project requiring an architect, budget for the scope of design, coordination and construction-stage services. The architect can add value; the practical issue is to include the cost and responsibilities before finalising the pro forma.

Reference: BC Architects Regulation, section 5.

Six units do not automatically mean Part 3

The architect threshold and the Building Code pathway are different tests. Part 9 can apply to qualifying residential buildings of up to three storeys and no more than 600 square metres of building area; the full code scope and occupancy must be checked. A six-unit building is not automatically a Part 3 building.

Stacked layouts still deserve careful review for fire and sound separation, exiting, accessibility and structural design. Ask which consultants and reports each concept requires, rather than assuming a fixed consultant list for every sixplex. Vancouver uses its own Building By-law, so confirm the applicable rules there.

Code overview: City of Surrey — Part 9 and Part 3 definitions.

Servicing can change the economics

Ask the design team and utilities to assess water, sewer, drainage and electrical capacity for both concepts. A site may need upgraded connections or other work; the need and cost depend on existing capacity and the design. Carry realistic allowances until quotes are available.

City fees: use the current schedule for your exact project

Do not rely on another builder’s fee total. Development cost charges, levies, amenity charges, permit fees and frontage works can use different calculations and exemptions. Additional floor area or units may increase charges, but the difference needs a site-specific calculation.

BC’s general development cost charge exemption for fewer than four self-contained residential units is subject to local bylaws and regulations. A fourplex is not automatically exempt.

Vancouver’s framework changed in 2026. Its new Amenity Cost Charge By-law took effect September 30, with transition provisions for applications already in progress. Older multiplex density-bonus examples should not be used as current quotes. Confirm the charges and application-date rules with the City.

Sources: BC — DCC exemptions; Vancouver — Amenity Cost Charges and transition provisions.

Parking and liveability are part of the investment

Check the rules for the address, not just the city. Provincial restrictions on parking requirements apply to specified small-scale housing near prescribed frequent bus service, as well as to residential uses in designated transit-oriented areas. These are specific legal categories, not a blanket exemption near every bus stop.

Where parking is required, test stall dimensions, access and turning space before treating the concept as feasible. Where minimums do not apply, assess the intended residents’ transport needs and buyer or tenant expectations.

For illustration, a requirement of 1.5 stalls per unit would mean six stalls for a fourplex and nine for a sixplex. This is arithmetic, not a statement of the current requirement in any municipality.

Liveability also depends on usable outdoor areas, privacy, daylight, sound separation, storage, bins, deliveries and EV charging. A good sixplex can address these needs; a poorly planned fourplex can overlook them.

For strata projects, clarify responsibility for shared repairs, insurance and common areas. Fewer owners do not guarantee fewer disputes. These design and management choices can affect operating costs and resale appeal, so include them in the comparison.

Parking framework: BC Local Government Act, sections 525.1 and 525.2.

Fourplex vs sixplex: what to compare

When can a sixplex be the stronger option?

A wider or larger lot, an efficient design, good transit access and supported demand may make the extra homes worthwhile. For a long-term rental hold, the financing comparison can be particularly important.

CMHC’s MLI Select requires a minimum of five units for standard rental housing. That can make a qualifying five- or six-unit rental project eligible for a financing pathway that a standalone four-unit project does not meet.

Unit count is only the starting point. The project must satisfy the program’s requirements and commitments, alongside lender and CMHC underwriting. Compare rent, operating expenses, debt service, premiums, available proceeds and timing before relying on an insured take-out.

For homes intended for strata sale, assess sale prices, absorption and mortgage-release conditions instead. Decide whether you will sell or hold before choosing the financing structure.

Program guidance: CMHC — MLI Select eligibility and requirements.

Run both scenarios before committing to drawings

1. Confirm the site envelope. Obtain zoning, survey and preliminary layouts, including access, trees, setbacks and any easements.
2. Price the design team and servicing. Request scope and fee estimates for both concepts, with unresolved items clearly identified.
3. Get current charges. Confirm municipal and regional fees, payment dates and any applicable exemptions or transition rules.
4. Support the revenue. Use comparable sales or rental evidence suited to the actual unit sizes, layouts and parking.
5. Map the cash requirements. Compare total costs, cash before and between draws, contingency, interest carry and a delayed-exit scenario.
6. Review financing and the exit together. Compare achievable loan proceeds and terms, then profit or rental cash flow relative to the equity invested.

For an initial lender review, bring the property address, ownership and existing debt, both concept budgets, available funds, builder experience and your intended sale or rental strategy. The best unit count is the one supported by the complete analysis.