Modern Coach House on Charlton

The property was purchased by Emma & Graham Cubitt in 2005 when they first moved to Hamilton, in part because it was a double-wide lot in the Kirkendall neighbourhood with the future potential for development of a second dwelling. An old shed and the back yard had for years been neglected and underused. The property is a few doors down from the HAAA park backs onto Ryerson Middle School and has no laneway access, so the new development would need to allow for secondary dwellings (or SDUs, sometimes called garden suites) because of the lack of laneway access.

Emma’s masters thesis on incremental intensification through urban alley infill developments had led to a decade of advocating for a zoning to allow SDUs across the city. With no certainty of this vision being fulfilled, but a desire to demonstrate that it would be both technically and financially feasible, they decided a prototype was needed to help the idea gain traction in the community. They also wanted to demonstrate these types of buildings could be built to the Passive House standard, enabling low-energy, low-carbon all electric living.

By mid 2020, the design was finalized and a permit issued for a garage/workshop – but one which could be readily converted to a dwelling whenever an SDU bylaw was in place. The Cubitts were able to refinance the primary house to fund the new building. Just Working Construction built the coach house between November 2020 – February 2021. Fortunately, the City’s planning staff were implementing a new SDU bylaw simultaneously, which Council approved in May 2021. This fortuitous timing enabled them to submit for a building permit to convert the garage/workshop into a secondary dwelling. This interior work was quickly completed in August-September 2021, and a family of four moved in immediately.

Costs of constructing the SDU

The final construction cost was $320,000 + HST. Including the insulated garage area, the total GFA is 110m2 (1,183ft2), or $270/ft2 + HST. Softs costs were $15,000 for architectural & engineering drawings, $1,000 for both permit applications, $3,500 for reduced development charges and $600 for a minor variance. Site landscaping costs were an additional $20,000 (for the SDU portion of the property). An HST refund application was submitted at the end of the project, with a 60% refund bringing HST down to $16,000. Total project cost was $375,000.

The construction costs are broken down as follows:

  • $40,000 General Conditions, Miscellaneous, Overhead & Profit
  • $4,000 Excavations
  • $15,000 Foundation (structural slab)
  • $24,000 Underslab insulation & Exterior wall insulation (5.5″ between studs + 3″ exterior Roxul Comfortboard)
  • $50,000 Framing*
  • $24,000 Windows & front door (all Passive House certified)
  • $33,000 Maibec siding
  • $12,000 Metal roofing
  • $22,000 Drywall
  • $5,000 Stairs & railing
  • $7,000 Kitchen Millwork & Appliances
  • $7,000 Interior Doors & Trim
  • $18,000 Interior finishes (Tile, Wood Flooring, Painting)
  • $25,000 Plumbing (Includes all new sewer drains in basement of the main house and the service connections for water and sanitary from the main house to the coach house)
  • $3,000 New 1″ water service upgrade to the property from City mains
  • $10,000 HVAC (Heat pumps & ERVs)
  • $20,000 Electrical & Lighting

A prototype for future SDUs

With a total GFA of 110m2 including the garage, or 75m2 not including the garage area, this SDU of 22′ x 27′ can fit seamlessly in to many lots in Hamilton. Houses like this can provide ample living space for a family of four, with two bedrooms and two washrooms. With the “upside down” typology with the bedrooms below and kitchen/living spaces above, the girls who now live in the house call it their “tree house” because the living spaces are literally up in the trees. This type of layout would also work well for a home office. We hope this prototype for sustainable living will be something that can be replicated on other properties across the city as one part of the solution to the housing crisis.

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