St. Catharines · Garden Suite Construction
Garden Suite Construction in St. Catharines
Four pre-approved detached ADU designs, from 37 m² to 80 m², are published by the City of St. Catharines through its Housing Accelerator Fund work. They are already reviewed for the Building Code and for zoning size and height. The City estimates about $130,000 plus HST for the smallest, the 37 m² Beech.
Garden Suites in St. Catharines
What’s different in St. Catharines
| Permit office | City of St. Catharines Planning and Building Services (official site, opens in a new tab) |
|---|---|
| Units per lot | Up to two accessory units, one or both detached, under By-law 2024-032. |
| Pre-approved designs | Four models, 37 m² Beech to 80 m² OCI large. Setbacks, servicing and parking checked per lot. |
| City cost estimates | About $130,000 plus HST for the Beech model to $225,000 for the OCI large. |
| Parking | 0.5 spaces per accessory unit: one space covers one or two units. |
| Development charges | Exempt for a qualifying detached unit. Permit fees still apply. |
| ADU grant | Up to $80,000 for detached units until funding ran out in April 2026. |
Worth knowing first
Grantham and Merritton lots have room for a backyard unit
Post-war lots in Grantham, Western Hill and Merritton are deep enough to place a single-storey unit well behind the main house. They have a straight run for sewer and water and a side yard wide enough for access. In Merritton, some owners replace an old garage with the unit, because accessory buildings share one lot coverage limit. The City’s estimates don’t reflect every site. Trenching 30 m (100 ft) of sewer and water, a hydro upgrade, tree removal and a frost-protected foundation on clay can add $40,000 to $120,000. We separate building and site costs on the quote.
The scope, pricing tiers and 5-step process are the same everywhere we work. See Garden Suite Construction ›
Frequently asked questions
Garden Suites in St. Catharines: three local questions
Yes, if your lot meets the setbacks, parking and servicing for that design. The 4 pre-approved models run from 37 m² to 80 m² (about 400 to 860 sq ft) and are reviewed for the Building Code and zoning size and height. Planning and Building Services still checks setbacks, parking and connections for your property. We measure the yard and confirm sewer depth and side-yard access first.
Only half a space per unit. Zoning By-law 2013-283 requires 0.5 parking spaces per accessory dwelling unit, which works out to 1 space for one or two units, on top of the main house’s requirement. On a single-wide driveway that can decide the project. A tandem space or a widened driveway can solve it, subject to curb-cut rules. We check parking on your survey first.
Through the main house’s existing connections. The unit’s drain ties into the house sewer lateral, and a new water line branches from the main supply, sized for two households. Gravity drainage works when the lateral is deep enough. Otherwise a pump is required. Hydro comes from Alectra Utilities as a sub-feed from an upgraded 200 A panel. Runs over 30 m (100 ft) add noticeably to the cost.
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