Don't Make These Mistakes When Buying a Secondary Suite

What is a Secondary Dwelling Unit?

A secondary dwelling unit, sometimes referred to as a secondary suite, an in-law apartment, or an accessory dwelling is a self-contained living space within an existing home. These units are different from renting out a room in your home, as they have their own private kitchen, bathroom, and living room.

These types of units are becoming increasingly more popular, both for homeowners due to the costs of long-term care for parents and relatives, or the need for additional income because of their affordability.

In this article, we’re going to highlight some important considerations before buying a new home or designing a secondary unit in your existing home.

Before You Buy Consider:


One aspect that seems simple but may get lost in the shuffle is how your tenant will access their unit. You may be thinking, “Well, the house already has a front door, right?”

Unfortunately, renting out a secondary dwelling isn’t as simple as giving someone your house key. A secondary suite is a rental unit inside your home, remember. It’s a completely separate space—and that means you need to follow some rules.

For instance, According to the City of Kingston:

Access to second residential units in existing dwellings shall be provided by means of the front entrance of the street, or by a 1200mm walkway down the side yard of the property. The second residential dwelling unit shall be provided with:

  • A separate exterior entrance located at the side, rear or front of the principal dwelling unit, or
  • A separate entrance provided through a common entrance vestibule within the principaldwelling.

These rules vary with every municipality, as a part of their zoning requirements. So, what does this mean? To state it simply, this means you need to provide your tenant with either a private entrance on the exterior of the building that accesses their unit directly (like a walkdown or walkout), or, alternatively, you can build a vestibule or foyer and provide them with a door to
access their unit from there.

When inspecting a home, one thing you should look for is how easy it would be to build a vestibule. For example, if you’re envisioning a basement unit, it’s good if the stairs are close to the entry way; this way, you can make the top of the stairs the private entry for your tenant. Remember, you can’t go through one unit to get to another unit.


Zoning is perhaps the most important aspect when developing a secondary unit. Before we get into the details, we want to stress how important it is to check the appropriate zoning for your area prior to purchase, as zoning can cause you a great number of headaches. Not sure where to check? We can help!

At the end of the day, we can renovate any part of the inside of your house, but we cannot move your house to a new zone. With that said, there are so many zoning-related items to highlight that we couldn’t possibly list them all here. This is why we suggest that everyone books a zoning check with us—which is available online.

However, the three most important things you should keep in mind are:

  1. The secondary unit requires a private kitchen
  2. You must provide access to a laundry room, though it can be shared between units, provided that both units can access it without going thru the other unit
  3. Windows are required to allow natural light into both the bedroom and the living room. When considering windows remember that it is much easier to enlarge or shrink windows than it is to install new ones.


Plumbing can be a major obstacle to overcome when searching for a home that can support a secondary unit. The Ontario Building Code has a minimum set of requirements that includes access to hot and cold water, a bathroom sink, a bathtub or shower, a toilet, a kitchen sink, and access to laundry facilities. Which is a lot of requirements and means not every home is suited for a secondary suite.

Determining whether or not a home’s plumbing can support a secondary unit is something you may be able to do yourself. The first step is to find a drain into the current plumbing, like a laundry tub. Once you’ve found one, you’ll need to figure out if it “pumps up” or “pumps down.”

A “pump up” requires a motor to grind sewage and pump it into the waste system (typically a septic tank). While a “pump down” or “gravity drain” requires no pump. Making this determination is important, as septic tanks are sized for the house and were not, when originally installed, considering that an extra unit and family would be occupying the space.

How to Find a Good Contractor

House of Three has many trusted contractors and can provide recommendations if you’re not sure where to start. However, if you intend on finding a contractor yourself, we recommend you look for a “General Renovation Contractor” and ask about their experience with secondary suites.

We recommend you look for this type of contractor, as they are investment oriented and are familiar with this process specifically. They will ask the right questions, know the correct lingo, and are better able to source materials.

Final Advice From Your Trusted BCIN Designer

Here are some of our more unique pre-designed blueprints for you to take a look at if you need ideas.

This is a garage design that uses a deck as its second storey. This would be ideal for a waterfront lot, cottage, or other recreational property that needs seasonal storage and entertaining space but doesn’t need a full residence.

Timing is Important

Don’t leave things to the last minute; we’ve seen clients be unable to get a building permit in time, be unable to have their lawyer close in time, and these are avoidable headaches. We strongly suggest you provide us with a minimum of 6 weeks before closing in order to avoid issues.

You're Not Living There!

Sometimes clients are insistent on large bedrooms or spacious living rooms. A client once had the kitchen reconfigured multiple times because he wanted a show stopper kitchen to maximize resale value—but it was a two-bedroom basement apartment was bought as a long term investment. They didn’t need a 5-star kitchen. Keep your rental units clean, affordable, and well maintained, and your tenants will be happy.

Remember, it’s a rental home—not your dream home.

Thank you for reading and we hope this has inspired you or given you guidance on your secondary dwelling journey. If you have any further questions or are interested in setting up a consultation with one of our trusted BCIN designers, you can reach us by following this link.

Want to read more?

Check out our previous blog post if you’re looking to start a custom build. Our Guide to Buying Land in Ontario covers everything you need to keep in mind when in the market for new property.