What Is a Carriage House? The Original Backyard Suite

Of all the words for a backyard home, “carriage house” is the one with the longest history and the least regulatory meaning. It describes a real building type that exists on thousands of older Canadian lots — and if you have one, you are sitting on the cheapest starting point for a second dwelling, provided you go in with accurate expectations about what converting it involves.

This guide covers what a carriage house actually is, how it relates to the coach house, what a conversion genuinely requires, what the sizing rules look like when you build new, and how to judge whether it is worth doing.

What is a carriage house?

A carriage house is a detached building in the rear yard of a property, originally constructed to store a horse-drawn carriage and often to stable the horses, with living quarters above for the coachman or groom. They were built in quantity in Canadian and American cities through the nineteenth and early twentieth centuries, on lots that backed onto service lanes.

When cars replaced carriages, most of these buildings became garages. Many were demolished. The ones that survived tend to sit on older, deeper lots in established neighbourhoods — which is exactly where a second dwelling is most valuable today.

In current usage, “carriage house” means one of two things: an original historical structure, or a newly built detached rear-yard home designed to evoke one. Both end up in the same regulatory category — an accessory dwelling unit, secondary to the main house, sharing the lot and normally the title.

Carriage house vs coach house

Historically these were the same building. “Coach house” and “carriage house” both described the outbuilding where the vehicle was kept, and the two words survive side by side out of regional habit rather than any legal distinction.

The practical difference today is only which one your municipality writes into its bylaw. A small number of Canadian municipalities — Surrey and Ottawa among them — use “coach house” as the live planning term. Almost none use “carriage house”: it is now descriptive language rather than a regulatory category. If you are looking for the rules that apply to you, search your city’s own word, which may be coach house, laneway house, garden suite or backyard housing depending on where you are.

That is the whole of the distinction, and it is worth spending no more time on. What actually determines your project is the condition of the structure and the rules of your municipality.

Can you convert a carriage house or garage into a legal suite?

Often yes — but “convert” undersells the work, and this is where budgets go wrong.

A building constructed to shelter a vehicle was never designed for year-round human occupancy. Converting it to a legal dwelling means bringing it to the same standard as new construction in most respects. Expect to deal with:

• The foundation. This is the big one. A garage slab is typically shallow, unheated and not built to carry an insulated, occupied structure through frost cycles. It usually has to be replaced, which means the “existing building” saves you less than you’d expect.
• Insulation and the building envelope. Walls, roof and floor all need to meet current energy requirements. In an older structure this often means opening everything up.
• Egress. A dwelling needs compliant means of escape — window sizes, door swings, and stair geometry if there’s a second storey. Original carriage-house stairs almost never comply.
• Fire separation. Required between the dwelling and any remaining garage space, and to neighbouring structures depending on setback.
• Servicing. Water, sanitary sewer and adequate electrical capacity have to reach the building. An existing garage may have a single lighting circuit and nothing else.
• Structure. Century-old framing may need reinforcement to carry modern loads and modern insulation weight.

The heritage caution. If the property is heritage-designated, you need heritage approval before you can get building permits, and that review can constrain what you’re allowed to change on the exterior. This is not a reason to abandon a project, but it is a reason to start the heritage conversation early — finding out after you’ve paid for drawings is expensive. Designation also sometimes brings access to conservation grants, which is worth asking your municipality about directly.

The honest summary: converting an existing structure is usually cheaper than building new, but by less than most people assume, and the gap narrows further the older and rougher the building is. Get a structural assessment before you commit to a number.

Building a new carriage house: what the rules control

If you’re building new, municipal rules will control the same handful of things everywhere, even though the numbers differ: height, site coverage, floor area, setbacks, separation from the main house, and design treatment.

Edmonton is a useful worked example because its current bylaw is unusually explicit. Under Section 6.10 Backyard Housing of Zoning Bylaw 20001, the City sets:

• Maximum height: 6.8 m — dropping to 4.3 m where the rear lot line abuts a residential site with a height limit of 12.0 m or less
• Maximum site coverage: 20%
• Maximum second-storey floor area per dwelling: 60.0 m², rising to 70.0 m² where the building meets the bylaw’s Inclusive Design requirements
• Minimum setback: 1.2 m, reduced to 0.6 m at the rear where it abuts an alley and no garage door faces it
• Minimum separation: 3.0 m from other principal buildings on the site
• Required: a main entrance separate from any garage door, plus a covered entrance feature

Note what that 60 m² figure actually is — a cap on the second storey, not on the whole unit. It is frequently repeated online as a total floor-area limit, which is wrong and would make the building sound far smaller than the bylaw permits. This is a good illustration of why the current bylaw text is worth reading rather than a summary of it.

Edmonton’s bylaw also states plainly that backyard housing must not be subdivided from the principal dwelling on the site, or form part of a bare land condominium — which answers the “can I sell it separately” question definitively for that city.

Every one of those numbers is municipality-specific. Toronto, Vancouver and Calgary set different heights, coverages and setbacks. Use Edmonton’s as a shape, not as your numbers.

What does it cost, and what does it rent for?

We don’t publish a national figure, because a credible one doesn’t exist — a conversion of a sound structure and a new two-storey build are different projects by a wide margin, and provincial cost bases differ too (B.C. charges 7% PST on many construction inputs; Alberta has no provincial sales tax).

What actually drives the number:

• Foundation — whether the existing one can stay, which for a garage slab it usually can’t
• Servicing distance — how far water, sewer and power have to travel to the rear yard
• Whether it’s one storey or two — a second storey adds stairs, structure and often triggers stricter height and setback rules
• Structural condition — for an original carriage house, the single largest unknown until someone opens it up
• Heritage review — where applicable, both a timeline and a design-constraint cost

On rent, a detached unit generally outperforms a basement suite of the same size, because a tenant gets a private building and their own front door. But your local one-bedroom market sets the ceiling, and any projection that ignores vacancy, maintenance and tax on rental income isn’t a projection.

Is a carriage house worth building?

It’s most likely to work when you already have a sound structure worth saving, when servicing is close, when the lot is deep enough that the build doesn’t consume the usable yard, and when you’re holding the property long enough for rent to repay a substantial capital cost.

It’s least likely to work when the existing building needs a full foundation replacement anyway — at which point you’re paying new-build prices for a constrained footprint and an awkward layout, and building fresh may give you a better unit for similar money. Being honest about that comparison early saves people a lot of money.

There’s also a middle case worth naming: some original carriage houses are worth restoring for reasons that aren’t purely financial — they’re characterful buildings on characterful lots, and the finished result is often more appealing than anything new. That’s a legitimate reason to proceed. It just shouldn’t be mistaken for the cheap option.

Our how it works page walks through how a project like this moves from feasibility to approvals to build.

See whether your existing structure is worth saving

The most useful question about a carriage house isn’t what to call it. It’s whether the building you already have can be converted economically, or whether you’d get a better unit for similar money by starting fresh — and that turns on the foundation, the servicing distance and your municipality’s dimensional rules.

HouseLyft’s free property assessment works through those specifics for your address. If you want background first, our secondary suites overview and zoning and bylaws guide cover the ground. When you want a straight answer about your own backyard, request your free report.