City of St. Thomas

The designs that are available for use in St. Thomas include options for Detached Additional Residential Units (ARUs), fourplex, sixplex and stacked townhouse modules. Designs were developed by architecture and engineering professionals and are designed to be:

• adaptable for a range of accessibility needs;
• energy efficient & climate resilient;
• cost-effective through standardization;
• reflective of regional climate zones, housing needs, and construction methods; and
• compliant with provincial codes and regulations.

The City of St. Thomas has pre-reviewed and supports the use of the following Ontario region designs from the CMHC Housing Design Catalogue: Accessory Dwelling Unit 01, Accessory Dwelling Unit 02, Stacked Townhouse 01, Stacked Townhouse 02, Fourplex 01, Fourplex 02, and Sixplex.


Credit: Canada Mortgage and Housing Corporation. ADU 01 (ON)

The Accessory Dwelling Units (known in St. Thomas zoning as ARUs) and fourplex types may work in most residential zones in St. Thomas except higher density zones where the sixplex and stacked townhouse designs may work.¹

^{1. Please note that not all housing types are permitted on every lot.  Zoning regulations for each permitted use such as, setbacks, lot frontage, lot coverage, parking and driveway widths will apply.} 

The benefits of using the Catalogue include:

• Cost effective - Using Housing Design Catalogue plans can save you money and time as you do not need to create plans from scratch. The plans are available to property owners free of charge and may be used by you and your qualified professional to assist you to complete user choices, locate the building on a site and design a foundation, parking areas and walkways, and plan for site services.
• Timely review - All small-scale residential projects (including Catalogue designs) will be reviewed for through the building permit process within 10 business days.  While each project must be reviewed for compliance based on the individual lot conditions, staff has pre-reviewed the Catalogue designs for general zoning by-law and building code compliance.
• Efficient inspections - Building inspectors will be familiar with the Catalogue designs.  Inspections can be requested though Building Services and are typically scheduled for the next business next day.

The Catalogue designs are ‘near permit-ready’.  They are code compliant and ensure the building architecture and systems have been designed so that the modifications required to prepare permit-ready drawings are minimal.

You will require a ‘qualified professional’ (for example a licensed designer with BCIN number or architect or potentially an engineer as needed) to assist in finalizing a ‘Derived Design’ (see Catalogue User Guide) so that they are adapted to your unique site conditions. 

This includes but is not limited to:

• designing a foundation/basement suitable for your site grading
• preparing a site plan to show how the building, parking, walkways, etc. will be laid out to comply with zoning
• preparing site servicing drawings 
• confirming heat load calculations
• selecting accessibility features
• selecting energy efficiency features

The designs also allow for individuals to make a design their own through material selection and aesthetic design choices. Colours and materials for cladding, roofing, and interior finishes will also need to be selected and incorporated into the design by your ‘qualified professional’.  The renderings provided in the Housing Design Catalogue are illustrative examples only.

• Understand your lot and the zoning rules to determine what plan will work on your lot.
• Check your survey to confirm lot size and easements,
• Look for infrastructure such as hydrants, streetlights, street trees, etc. that your project should avoid.
• Confirm the zoning rules that apply to your lot.  The zoning will permit up to 4 dwelling units on most residential lots subject to meeting regulations such as: minimum lot frontage, minimum number of parking spaces, maximum driveway or parking lot size, minimum building setbacks, maximum building height, minimum landscaped areas and providing unobstructed walkways.
• If considering an ARU, consult the City of St. Thomas ARU Guidebook.  The guide provides:
• Illustrations and examples of different Additional Residential Unit types and considerations
• a helpful overview of updated zoning regulations
• an overview of permit and approval processes
• a one-page checklist summary for your project
• answers to frequently asked questions about ARUs
• additional web resources and relevant contact information.
• Review the Housing Design Catalogue and User Guide, pick your plan, and download the technical design package.
• Retain a ‘qualified professional’ to help you complete your Derived Design based on the Catalogue plans and help you prepare a site plan, foundation plan and servicing plan.
• Visit Building Services for links to more information about Building Permits and submissions through the online portal.