Adding a secondary suite by renovating existing space is not automatically cheaper or faster than building new. Here is how the two paths actually compare.
Written by Serge, Founder, Kelowna Carriage Homes
A homeowner adding a rental unit generally chooses between renovating existing space, usually a basement or a garage, into a secondary suite, or building a new detached carriage home in the back yard. Both routes can produce a fully legal, permitted unit. The right one depends on the lot, the existing structure, and the budget, not on which is inherently better.
A secondary suite conversion generally runs $60,000 to $150,000 and moves faster than new construction, since the foundation, framing, and roof already exist. Construction time is often measured in weeks to a few months rather than the 5 to 8 months a new structure takes.
That speed depends on what the existing space allows. A basement with adequate ceiling height, a legal egress window path, and reasonable access to plumbing lines converts efficiently. One without those, needing excavation to lower the floor or a full new plumbing run, closes much of the cost gap with new construction.
A turnkey carriage home generally runs $350,000 to $550,000, based on 2025 BC laneway-home cost data, with 3 to 5 months of design and permitting followed by 5 to 8 months on site. The cost is higher, but the result is a fully separate structure with its own private yard and parking, typically commanding higher rent than a basement suite in the same neighbourhood.
New construction also means full design freedom: the layout is not constrained by an existing foundation or ceiling line, which matters if the goal is a two-bedroom unit or a specific accessibility feature.
Renovation makes sense on a tight lot without room for a detached structure, where the existing basement or garage already has usable ceiling height and natural light, or where the budget or timeline cannot support a multi-season build. It also suits an owner who wants rental income sooner rather than a larger structure later.
Building new makes more sense when the lot has room, when the main house has no usable convertible space, or when the goal is the higher rent and full privacy a detached unit provides. It is also the only option when the desired unit would exceed what a basement or garage footprint can hold.
A renovation can carry its own hidden costs: cutting a new egress window into a foundation wall, adding a separate electrical panel and meter, fire-rating the ceiling or walls between units, and correcting moisture or insulation issues common in older basements. A new build carries different ones: distance from the property to the water and sewer main, site grade, and tree removal all move the price before a single wall goes up.
A practical rule: if a basement conversion needs a full new staircase or a major structural opening to meet code, the cost gap with a new carriage home narrows considerably, and the decision comes back to which structure suits the lot and the long-term plan.
More on new-build costs is on the carriage homes page; more on conversions is on secondary suites.
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Costs, timelines, rents, and incentive amounts on this page are estimates from the sources cited, current as of September 2026. Each is confirmed in writing in your free feasibility study. Licensed and insured; documentation available on request.