Building a Second Suite

For years, many local governments discouraged or even outlawed the creation of self-contained living spaces called – “second suites” – in basements. I’m not sure why, but it probably had to do with fears of over crowding in neighbourhoods, with too many cars parked in the area. You may live in a region where the big shots still think second suites are a danger and make it illegal for anyone to live separately in a basement. On the plus side, having self-contained basement accommodation can help make homeownership more affordable and provide much-needed space for people who don’t need a full-size house.

The thing is, if you’re planning to make your finished basement into a truly separate (and legal) place to live for tenants or relatives, you need to build in features that aren’t necessarily part of typical finished basement construction. The requirements for a legal and practical second suites are higher than a regular finished basement and involve extra measures for fire safety, sound control, exiting the building, parking, sewage disposal and lack of commercial activity in the suite. It all makes good sense, too.

When my wife and I got married in 1988, we lived in the basement apartment at my grandfather’s house in Toronto, Canada for a few years. That let us save money and get our feet on the ground. That was the same basement apartment where my parents lived for a few years when they stepped off the altar in 1962. I’m not sure this little basement apartment was completely legal for either of us, but I didn’t want to check with the authorities in case it wasn’t. The ability to live very economically was something we needed.

Since you haven’t built a second suite yet, it’s wise to contact someone in local authority to find out exactly what’s required. As with most things in the world of building and renovations, details vary from place to place.

Second suites are usually defined as a separate living space within a single family dwelling. Total floor area of the second suite is usually limited to somewhat less than half of the total building size. Requirements for second suites in basements will vary from municipality to municipality, but these are the general features that a building inspector might look for:

Basement Suite Size & Ceiling Heights

Most second suites can’t be larger than about 1000 square feet, and they must be less than 40% of the total living space in the home above. That’s a rule of thumb, so check your local bylaws. Minimum ceiling height underneath beams, ducts and any other drop-down features is 78”. If your whole basement is too big for a second suite, you can simply include only part of the basement as finished living accommodation. That’s the best way to get around the maximum size restriction, though you’ll rarely have to do that. Basement need spaces for utility equipment and mechanicals, and these don’t need to be included in the 1000 square foot maximum size.

Second Suite Fire Separations

A second suite must typically be able to contain a fire and prevent it from spreading to the main living area for 45 minutes of burn time. One thickness of 5/8”-thick fire code drywall on each side of a wood frame wall satisfies this requirement. A single sheet of the same thing will do the job on ceilings.

It can get tricky meeting fire separation details where heating ducts or pipes extend between the main living area and the second suite. Hot water radiators or electric heating systems that don’t involve an exchange of air from one suite to another makes it easier to achieve this. Hard-wired, ionization smoke alarms will also need to be installed in both the main and secondary living spaces, plus a carbon monoxide detector if the building has a garage and/or any kind of fuel burning appliance. Installing a sprinkler system in the entire building often eliminates the need for some fire separation requirements. It might be easier to install a sprinkler system than a fire-resistant wall.

Basement Doors & Windows

Your second suite must have it’s own full-size entry door. This goes without saying, but it’s worth thinking about right up front. Where would you put such an entry door? Alternatively, windows in each bedroom must also be large enough and of a design to allow people to get out in the case of an emergency. This is the “egress” windows I spoke about earlier. As with most bedrooms in above-ground accommodations, bedrooms in basements must also have electrical outlets protected by arc fault circuit interruptors (AFCI). Click here for the previous lesson on AFCI and other electrical protection technology.

Second Suite Plumbing

Naturally, second suites need a kitchen sink, bathroom, toilet and a shower or bathtub. Some jurisdictions also require a minimum 3/4” diameter water supply pipe leading from municipal system. Some homes only have a 1/2” supply line, and this can’t deliver enough water flow to what amounts to potentially two households under the same roof. It could be fairly costly to have a 1/2″ diameter line upgraded to 3/4″ diameter, so check with municipal authorities as you plan. You can determine the diameter of your current line by measuring it where it comes in your basement. You’ll find 3/4″ diameter water line measures closer to 7/8″ outside diameter. That’s because in the world of plumbing, pipe and fitting sizes reflect the smallest inner diameter of a fitting the might be involved in the installation.

Heating & Ventilation Systems

Second suites are often required to have independent methods of heating, not merely extensions of the system used in the main part of the house. The idea here is to limit the spread of fire through things like forced air furnace ducts. Where heating or ventilation ducts do extend from one living area to another, a duct-style smoke detector and/or fire dampers keep fires from spreading to both living areas. Second suites also typically need both a bathroom exhaust fan and a kitchen range hood that exhausts air to the outdoors (as opposed to recirculating range hoods). If you have hot water heating, a single system is usually allowed since fire can’t spread where pipes go through walls and ceilings.

Second Suite Parking & Density

Most municipalities also require a separately accessible driveway for a legal second suite, and restrictions on home business occupations that may attract a regular stream of clients to the house. Only one second suite is usually permitted for any given home.