The lot was a 50-foot wide R3 in the older part of Kanata, off Castlefrank. Detached two-car garage at the back. The owners had been talking about a coach house since the City of Ottawa updated the zoning rules to allow them as-of-right on most residential lots.
They came to us in May 2025. Footings went in September. Tenants moved in March 2026. The unit rents at a reliable long-term rate including utilities, and the appraisal lift it added to the property meaningfully outpaced the build cost. The owners treat it as a long-horizon investment that pays back through both rent and equity.
Here is how the build came together.
The lot and the rules
Kanata has a mix of zoning, but most older residential lots are R1, R2, or R3 under By-law 2008-250. Coach houses, formally called secondary dwelling units (SDUs) when detached, are allowed on most of these lots provided you meet setbacks, lot coverage, and the height cap.
For this lot, the relevant numbers were: 1.2 metre side and rear setbacks, total lot coverage of accessory structures capped at 40 percent of the rear yard, height cap of 6.7 metres at the highest peak, and a maximum unit floor area of 80 square metres or 40 percent of the principal dwelling, whichever is less.
The principal house was 1,940 sq ft. Forty percent of that is 776 sq ft. We designed at 720 sq ft to keep a comfortable margin.
The free 48-hour lot feasibility review
Before we sign anything, we run a no-cost zoning and feasibility check on your lot. Setbacks, coverage, height, sewer connection point, and rough budget. We will tell you in two business days whether your lot can hold a coach house and what size makes sense. If it cannot work, we say so.
The plan
The brief was specific. The owners wanted a unit they would happily live in themselves if their adult kids ever needed a place. That set the bar above "rental finish" from day one.
720 sq ft, single storey above a slab. Footprint 24 x 30. Inside the envelope:
- One bedroom, 11 x 12, fits a queen bed plus a 10-foot wall closet
- Study, 8 x 9, big enough for a desk, file cabinet, and a daybed for guests
- Three-piece bathroom with walk-in shower, no tub
- Open kitchen and living, 14 x 22, with 10-foot ceilings
- Separate entrance off the side yard, with a 5x6 covered porch
- In-suite laundry tucked into a closet off the kitchen
The 10-foot ceilings did more for the feel of the space than any finish we picked. A 720 sq ft unit with 8-foot ceilings reads as small. The same plan with 10-foot ceilings reads as a designer apartment.
Servicing: where most coach house budgets blow up
Mechanical, water, sewer, and electrical from the principal house to the coach house was the single largest cost driver on this build, and the one people underestimate most. Trenching distance, sewer elevation, and panel capacity all swing this line item hard from lot to lot.
Water service: a new 1-inch line trenched 22 metres from the existing house service to the new unit, with a separate shutoff. The trenching length, the line, the lawn patching, and the inspection all factor in. Longer runs cost more.
Sewer: gravity drop to the existing sanitary connection at the front of the lot. We had to confirm the elevation worked before pouring slab. When a gravity drop is not feasible and a pump is required, this line item climbs.
Electrical: the existing panel had no room. We upgraded the principal house to 200 amp, ran a 100 amp subfeed in conduit to the coach house, and installed a separate meter. Whether your existing panel has spare capacity is a major swing factor here.
Gas: high-efficiency combi boiler for heat and hot water. Single appliance, no furnace, no separate water tank. Extension of the gas line from the principal house, separate meter, and the appliance install round it out.
Patching, restoration, and lawn re-seeding close out the servicing scope.
Where the budget goes
Every owner gets a detailed written breakdown before work begins. Here are the scope lines that make up a coach house build, ordered roughly by how much each one moves the budget. We itemize each so clients understand exactly what is included.
- Permit, BCIN drawings, site plan, survey
- Excavation, footings, foundation, slab, drainage
- Framing, roof trusses, sheathing, sheathing membrane
- Windows and exterior doors (high-performance triple-glaze)
- Siding (fibre cement plus a wood accent), soffit, eaves, fascia
- Roofing (architectural asphalt, ice and water shield)
- Insulation, vapour barrier, drywall, taping, paint
- Servicing (water, sewer, gas, electrical subfeed) — usually the single largest driver
- HVAC, plumbing rough and finish, electrical rough and finish
- Kitchen (in-house cabinet shop, quartz, appliances)
- Bathroom (tile, shower, vanity, fixtures)
- Flooring (luxury vinyl plank throughout, tile in bath)
- Trim, doors, hardware, finish carpentry
- Landscaping (entrance walk, side stairs, lawn restoration)
- Project management, supervision, contingency, final cleaning
The biggest variables between one lot and the next are servicing distance, finish level, and site conditions. Those three decide whether your build lands at the lean end or the premium end of the range.
The rental math, honestly
Tenants are a recently-retired couple on a reliable long-term lease that includes hydro and gas. The owners deliberately set rent mid-pack for the Kanata market because they wanted dependable long-term tenants, not maximum yield.
To work out payback honestly, take gross annual rent, then subtract the property tax delta, the insurance increase, a maintenance reserve, and minor repairs. What is left is net cash flow per year.
Divide the construction cost by that net cash flow and you get the number of years to recover the build from rent alone.
That is not the whole story. The build also lifted the appraised value of the property, and that equity gain materially outpaced the construction spend. The owners can refinance against it, sell into it, or leave it sitting.
Counting the equity gain plus the rent, the effective payoff is meaningfully faster than rent alone suggests.
The coach house is the best small-scale real estate investment available to most Ottawa homeowners right now. It uses your existing land, your existing services, and zoning that finally allows it.
What we would tell anyone considering it
Three things matter more than the design.
First, run the lot test before you fall in love with the idea. Setbacks, coverage, sewer elevation, and tree protection rules will make or break the project. We do this for free in 48 hours so nobody spends a year on a dream that the zoning kills.
Second, build it as a unit you would live in. A cheap rental finish trims the build cost a little up front, but it costs you in lower rent and faster wear for the next 25 years. The math is not close.
Third, plan for occupancy from the design phase. Separate entrance, separate utilities, separate parking, soundproofing in any shared walls. Tenants who feel like they are in a real home stay longer and pay reliably.
The build timeline week by week
For anyone considering a coach house build, this is roughly what the calendar looks like:
- Weeks 1-3: permit drawings, structural review, BCIN drawing set, City of Ottawa intake
- Weeks 4-9: permit review and revisions (Ottawa typical turn time)
- Weeks 10-12: permit issued, site preparation, tree protection fencing, lot stake-out
- Weeks 13-14: excavation, footings, foundation forms
- Weeks 15-16: foundation pour, foundation drainage, backfill, slab prep
- Weeks 17-18: slab pour, in-floor heating loops if specified
- Weeks 19-22: framing, roof trusses, sheathing, sheathing membrane
- Weeks 23-24: windows and exterior doors install, roofing
- Weeks 25-28: rough plumbing, rough electrical, rough HVAC, City inspection
- Weeks 29-30: insulation, vapour barrier, drywall, taping
- Weeks 31-34: trim, paint, kitchen install, bathroom install, flooring
- Weeks 35-36: finish plumbing, finish electrical, appliance install, final inspection
- Weeks 37-38: deficiency walkthrough, occupancy permit, final cleaning, tenant ready
From contract to occupancy: roughly 9 to 10 months on a typical Ottawa coach house. The permit phase eats about 6 to 9 weeks of that and there is no shortcut for it. We submit a clean drawing set on day one of permit intake, which keeps revision cycles to a minimum.
Curious whether your lot can hold one? See our coach house service page or call 613-862-4555 for the free 48-hour lot review.