02/01/2026
Thinking About an SDU in Your Ontario Home? What You Need to Know About Building Code Requirements
Adding a Secondary Dwelling Unit (SDU) ,sometimes called a secondary suite, basement apartment, or additional dwelling unit, is one of the most effective ways to increase housing options, create rental income, or improve long-term property value. In Ontario, SDU rules are shaped by both municipal zoning and the Ontario Building Code (OBC), so it’s important homeowners understand what the Code actually requires before you start construction or renovations.
Here’s what every Ontario homeowner should expect:
1. SDU Basics: Legal & Permitted
An SDU is a self-contained living space with its own kitchen and bathroom inside or attached to a single residential property. Under the updated 2024/2025 Building Code, a “secondary suite” has a clear provincial definition and is permitted in detached, semi-detached, and townhouse dwellings ,but only one SDU per property under the Building Code’s specific suite provisions.
2. Building Permits Are Mandatory
You must apply for a building permit before beginning work. Permit applications typically require detailed construction drawings that show how your suite will meet structural, mechanical, electrical, plumbing and fire safety standards under the OBC. Inspectors will review the work at key stages.
3. Ceiling Heights & Space Requirements
Secondary suites have slightly relaxed ceiling requirements compared to standard homes: 1.95 m (about 6’5”) minimum in most living areas, with a minimum of 1.85 m where ductwork or beams are located. These minimums ensure the space is comfortable and safe. Natural light and ventilation requirements, especially for windows, must also be met.
4. Egress & Fire Safety
Safe means of exit are critical. The OBC allows a shared egress route between the main unit and SDU in some cases, but most municipalities still require safe exits and escape paths (like egress windows or doors). Fire safety barriers ,typically 5/8” Type X drywall assemblies , are required between units to slow fire spread.
5. HVAC, Alarms & Independent Controls
Each dwelling unit must have its own thermostat and independently controllable systems. Smoke and carbon monoxide alarms are required in each unit and should be interconnected so that if one sounds, all units are alerted.
6. Zoning & Municipal Requirements
Even if the Building Code allows an SDU, you still need to check zoning rules in your city or town. Zoning can dictate where an SDU is allowed, how large it can be, parking requirements, and whether detached SDUs (like laneway or garden suites) are permitted.
7. Plan for Inspections & Compliance
Building Code compliance isn’t just about drawings — it’s about passing inspections at framing, insulation, plumbing rough-in, and final occupancy. Working with qualified designers, engineers, and contractors who understand OBC requirements can save time and money.
Adding or legalizing an SDU can make your property more functional and future-ready, but it’s not a DIY job unless you’re ready to tackle detailed technical requirements. Getting the permits and inspections right protects your investment and your family or tenants.
At Jaber Contracting Inc., we help homeowners navigate permits, design compliance and code-ready SDU builds that meet Ontario’s regulations while maximizing the value of your property. Let’s build it right from the start.
Transform your home with Jaber Contracting Inc., your one-stop shop for construction and renovation needs in Ottawa. From design to engineering to construction, we offer comprehensive services to bring your dream home to life. Get a FREE quote today!
