Multiplex forms: side by side, stacked, front and back, houseplex and courtyard

The names, and where each one is written down

Some names for small multi-home buildings are written into bylaws, and where a bylaw defines a word, that definition decides what a city will approve. One term comes first. A dwelling unit, which most bylaws shorten to unit, is one self-contained home. Surrey's Zoning By-law 12000 defines it as one or more habitable rooms used for living and sleeping, with cooking equipment (or the hook-ups for it) and at least one bathroom with a toilet, sink and shower or bath.

Each name in the table below counts principal homes. A principal home is a main unit. A secondary suite is a smaller home tucked inside a principal home. The difference matters because Surrey's duplex may hold a secondary suite in each half, which makes 4 homes in a building still called a duplex. Surrey's houseplex holds 3 or 4 principal homes and no suites at all.

Sixplex has no definition in any bylaw read for this guide. The word describes six homes on one lot, the number British Columbia's small-scale housing law requires cities to allow on lots of 281 square metres or more within 400 metres of a frequent bus stop, in the areas the law covers. A sixplex can be one building of six homes, or a mix of buildings and suites that adds up to six. The suites chapter of this guide shows how those mixes count.

Side by side: a shared wall from ground to roof

In a side-by-side layout, each home runs from the ground floor to the roof, and neighbours share a wall. Surrey's bylaw calls the two-home version on separate lots a semi-detached residential building: two structurally independent homes divided vertically by a party wall. The BC Building Code defines a party wall as a wall jointly owned and used by two parties, built on the line between two parcels of land that are, or can become, separate properties.

Because each home reaches the ground, each can have its own door at ground level. That fits Vancouver's definition, which gives every multiplex home its own direct exterior entrance, and Surrey's term ground-oriented, which it defines as a home with independent exterior access and a private open space other than a balcony or deck.

Each side-by-side home also has more than one storey. Sentence 9.10.9.16 (3) of the BC Building Code requires a home of 2 or more storeys, counting a basement, to be separated from the rest of the building by a fire separation rated at least 1 hour. A fire separation is a wall or floor built to slow a fire, and its rating is the time it is tested to hold. So the shared walls in a row of two- or three-storey homes are 1-hour walls.

Side-by-side homes can also be divided into separate titles. The province's policy manual notes that side-by-side homes in one building, built to the code, can be strata titled. Strata title makes each home a separate legal lot that can be sold, with the shared parts owned in common. Burnaby's R1 summary adds fee simple rowhousing, where each home sits on its own lot with no strata. The ownership guide on this site covers both routes.

Stacked: one home above another

A stacked layout puts one home on top of another. BC Assessment's actual use codes, which the province's policy manual lists, call the two-home version an up and down duplex and give separate codes for strata and non-strata buildings. In a stacked triplex or fourplex, some homes sit on the ground floor and others above them, reached by their own outside stair or a shared one.

Stacking changes what the floor between homes must do. Under Article 9.10.9.16, suites in a residential building must be separated from adjacent rooms and suites by a fire separation rated at least 45 minutes, and that includes the floor between an upper and a lower home. Article 9.11.1.1 sets a sound rating between a home and every other space where noise may be made, and the building code chapter of this guide gives the numbers. A floor carries sound the same way a wall does, so the floor design matters as much as the wall design in a stacked plan.

Exits change too. Article 9.9.9.3 requires a second and separate way out for a home whose door opens onto an exit stair serving more than one suite, a corridor served by a single exit, or an exterior passageway or balcony that serves more than one suite, has a single exit stair and sits more than 1.5 metres above the ground. A design that gives each upper home its own outside stair falls outside that article, because each stair serves one suite.

Stacked homes can be separate strata lots. Section 68 of the Strata Property Act places the boundary between strata lots in the middle of the wall, floor or ceiling between them. The limit the manual names applies to suites: a secondary suite cannot be strata subdivided from the main home it sits in.

Front and back: two buildings on one lot

A front and back layout uses two buildings, one near the street and one near the rear lot line or the lane. BC Assessment's codes group front and back duplexes with side-by-side ones, in strata and non-strata versions. Vancouver's definition allows a multiplex across one or more buildings on a site, and Burnaby's R1 district sets separate rules for front and rear principal buildings.

Burnaby's July 2026 summary shows how a city shapes this form. A front principal building may be 10 metres above grade, at 2.5 storeys for 1 or 2 homes and 3 storeys for 3 to 6 homes. A rear principal building may be 7.5 metres and 2 storeys. Both heights are 0.5 metres lower for a flat roof, and the storey counts include a basement or cellar. Front and back principal buildings must be at least 6 metres apart.

The rear building can be a principal building or an accessory one. Surrey defines a coach house as an accessory home above or attached to a detached garage, secondary to the main building on the lot. Burnaby treats buildings commonly called laneway homes as single-family dwellings, which it calls principal buildings. The next chapter covers these smaller rear homes.

Fire safety between two buildings on one lot depends on distance. The province's policy manual explains that the BC Building Code sets spatial separation rules to stop fire spreading from one building to another, and that those distances can be larger than the zoning setbacks. It says design changes or sprinklers can bring the two into line.

The houseplex and the courtyard

A houseplex places its homes inside the shape of a large house. Surrey's bylaw defines it as a multiple unit residential building of at least 3 and no more than 4 principal homes that resembles a large house, such as a triplex or fourplex, in which secondary suites are not permitted. From the street it looks like one house. Inside, the homes can be side by side, stacked or a mix of both.

Surrey allows the houseplex in its R3 zone, and only on a corner lot, a through lot or a lot with lane access. The Surrey chapter of the zoning guide covers those zone rules.

A courtyard layout turns the homes toward shared open space in the middle of the lot. The province's policy manual lists four detached homes, such as a cottage court, among the ways to place four homes on a lot. It asks cities to remove rules on which way the doors of non-principal homes may face, and names a courtyard arrangement or shared green space as a way to make new homes more livable. Burnaby's R1 summary lists cottage courts, meaning multiple detached single-family dwellings on one lot, among its allowed forms.

Which form fits a given lot is a separate question. Lot area, frontage and access decide it, and the unit-types chapter of the multiplex design guide covers that decision. This chapter only names the shapes, so that a plan, a listing or a bylaw makes sense when you read it.