Building an ADU in Hamilton? Here’s What You Need to Know
- John Barnhart
- Aug 7, 2025
- 3 min read
Updated: Aug 7, 2025
As housing costs continue to rise, more Hamilton homeowners are looking for ways to create secondary income, house extended family, or increase property value — and Accessory Dwelling Units (ADUs) are one of the most effective ways to do just that.
Whether you're planning a basement apartment in Westdale, a garage conversion in Stoney Creek, or a garden suite in Dundas, we’ll help you navigate the process from start to permit approval — with plans that meet Ontario Building Code and Hamilton’s unique zoning requirements.
🏘️ What Is an ADU?
An Accessory Dwelling Unit (ADU) — also called a secondary suite, in-law unit, or garden suite — is a self-contained residential unit located on the same property as a primary home. It can be:
A basement apartment
A detached backyard suite
A converted garage or loft
A unit above a detached garage
In Hamilton, ADUs are permitted on many residential properties, but you'll need to follow specific rules regarding zoning, size, parking, and design to get approval.
📍 Why Hamilton Is Embracing ADUs
Hamilton’s population is growing — and with that comes the need for gentle intensification. ADUs are one of the city's preferred ways to increase housing supply without changing the character of existing neighbourhoods.
🔹 Benefits of Building an ADU in Hamilton:
Rental income from long-term or student tenants
Multi-generational living without buying a second home
Increased property value and resale flexibility
Affordability for young adults or aging parents
🏗️ ADU Rules in Hamilton (2025 Update)
Every ADU project must follow both zoning by-laws and the Ontario Building Code. While specifics vary depending on your property and neighbourhood, here are some general guidelines:
✅ Zoning & Lot Requirements
Most R1, R2, and R3 zones allow one additional residential unit
Detached units (e.g. garden suites) must meet setbacks and access rules
Corner lots and wider lots are often easier to work with
✅ Ceiling Heights
Must be at least 6'5" (1.95m) throughout
Beams and ducts can be reduced to 6'1" (1.85m) in existing buildings
Some flexibility applies under Part 11 of the Ontario Building Code
✅ Egress & Fire Safety
Bedroom windows must meet egress requirements (minimum 3.77 sq. ft. clear opening, sill height no higher than 39")
Smoke and CO detectors must be hardwired and interconnected
✅ Plumbing & HVAC
Each unit must have a kitchen, bathroom, and laundry access
HVAC systems must be designed for safe airflow and temperature control
A heat loss calculation may be required for permit approval
🧱 Do You Need a Permit for an ADU in Hamilton?
Absolutely. All ADUs in Hamilton require a building permit with:
BCIN-stamped drawings
Site plan and zoning review
HVAC and heat loss design (if applicable)
Engineered foundation or slab details (for detached suites)
Skipping permits can lead to fines, delays, and major resale issues.
🧰 How The Building Permit Guy Can Help
We specialize in permit-ready drawings for secondary suites and ADUs across Ontario — and we know Hamilton’s zoning inside and out.
Our services include:
BCIN-certified drawings
Site plans
HVAC / heat loss calculations
Coordination with engineers (if required)
Full permit application support
Whether you’re a homeowner or contractor, we take care of the red tape so you can focus on building.
🎯 Ready to Start Your ADU Project?
We’re currently offering a limited-time promo on ADU drawing packages — check it out here:👉 thebuildingpermitguy.ca/adu-promo
Or get in touch for a free consultation:📧 info@thebuildingpermitguy.ca
📍 Serving Hamilton and all of Ontario
