Secondary Suites: A Guide for New Homes

This article is Part 3 in a series on Secondary Suites: Read Part 1, and Part 2 here.

There’s so much information available out there for homeowners looking to build secondary suites that it’s almost too much to take in. Yet despite all of that information, there is very little information to help guide the owners of new homes—because the law is different for you.

Homes built within the last five years are required to comply with new building code laws, meaning they must be in compliance with Section 9 of the Ontario Building Code. Unfortunately, the great guide provided by the Ontario government is a little sparse on details for owners who fall into the New Home category.

So, if you’re the owner of a new home, this guide will help answer some of your more detailed questions—questions whose answers you may be struggling to find online. However, please note this guide is not meant to be exhaustive.

Can I build a secondary suite on my property?

You will need a building permit to build a secondary suite on your property, and unfortunately, not every lot is suitable to host one. There are municipal by-laws, laws set out by the Ontario Building Code, and zoning requirements that can nix your plans, so it’s very important to get this right before you continue.

There are so many variables when it comes to zoning and permits that it would be impractical to try and list every requirement here. You will need to consult with a BCIN-licensed designer or your municipal planning and building office in order to complete this first step.

Outside your home, it’s important to make sure you have the space to install a ramp. A quick rule of thumb for determining if you’ll have room for a ramp is to add 10 inches of ramp for every inch of height. So, if your stairs are 10 inches tall, you’ll need 100 inches of ramp.

Does the age of my house matter?

Yes, it does. In order to maintain the quality of homes across the province, the Ontario Government requires that new houses comply with the latest building code standards; these standards are also how the government intends to increase the environmental efficiency of homes in the province.

What qualifies as a new home is, thankfully, quite simple.

If your home was built less than five years ago, your home is considered a new home and must comply with the latest standards. Why are there different building standards you might ask? Well, the Ontario Government sets out in Section 11 of the Ontario Building Code alternative requirements for old homes in situations where complying with the newest standards may be considered impractical.

Do rooms need to be a certain size in a secondary suite?

Because your secondary suite is an independent living space, the building code sets standards for what that living space must consist of. This includes what rooms must be a part of the unit (not shared) and the minimum size of those rooms. Fortunately, the room-size requirements for new homes and old homes are the same—though please note your local municipality may require larger dimensions in their bylaw.

Below you will find the minimum requirements as set out by the Ontario Building Code. Do note that in instances where an entirely separate room is not possible, the code sets out requirements for shared spaces, like a kitchen and dining room combo.

Room Dimensions
Room Minimum Floor Space
Living room 13.5 m² (145 sq. ft.)
Living room combined with a kitchen and a dining area (in a unit with sleeping accommodation for not more than two persons) 11.0 m² (118 sq. ft.)
Dining room 7.0 m² (75 sq. ft.)
Dining room if combined with other spaces 3.25 m² (35 sq. ft.)
Kitchen area and bedrooms combined with other spaces in dwelling units 4.2 m² (45 sq. ft.)
Kitchen in unit with sleeping accommodation for not more than 2 persons 3.7 m2 (40 sq. ft.)
Master bedroom without built in cabinets 9.8 m² (105 sq. ft.)
Master bedroom with built in cabinets 8.8 m2 (95 sq. ft.)
Bedroom without built in cabinets 7.0 m² (75 sq. ft.)
Bedroom with built in cabinets 6.0 m2 (65 sq. ft.)
Bathroom Sufficient space to accommodate a toilet, sink, and tub.
Living room, dining, kitchen and bedroom spaces combined 13.5 m² (145 sq. ft.)
City of Kingston: Housing Guide (PDF)
Ceiling Heights

When it comes to ceiling heights, things get a little more complicated. The height of your ceilings can greatly impact the location of your secondary suite, and new homes have strict requirements. For example, a common place for a secondary suite is the basement. However, basements can be tricky as their ceilings are often low, which can cause issues for living rooms which require 2300mm (7’-6 9/16”).

The dimensions for ceiling heights are very specific so please read the table below carefully.

Room Minimum Ceiling Height
Living room or space, dining room or space, kitchen or kitchen space 2300 mm over at least 75% of the required floor area with a clear height of 2100 mm at any point over the required area
Bedroom or bedroom space 2300 mm over at least 50% of the required area or 2100 mm over all of the required floor area. Any part of the floor having a clear height of less than 1400 mm shall not be considered in computing the required floor area
Basement space 2100 mm over at least 75% of the basement area except that under beams and ducts the clearance is permitted to be
Bathroom, water closet room or laundry area above grade 2100 mm in any area where a person would normally be in a standing position
Passage, hall or main entrance vestibule and finished rooms not specifically mentioned 2100 mm
Attic 50% of the floor area must have a ceiling height of 2030 mm. The other 50% of the floor area may have a ceiling height between 2030 mm and 1400 mm.
Stairs 1950 m (6’-5”) headroom
City of Kingston: Housing Guide (PDF)

Are there window and door requirements when building a secondary suite?

This may surprise you, but yes, there are both requirements for windows and doors and their sizes in your secondary suite. In fact, the Ontario Building Code is very specific when it comes to the size of your windows. This is to ensure that people are able to safely enter your home, and safely exit if there is an emergency like a fire.

The table below may be confusing to read at first, seeing as it uses “floor area” to determine the size of your windows. So, what does that mean? It means that if you have a living room that has an area of 13m2 (139.93 sq. ft.), your window must be 10% the size of that. So, the window in your living room would need to be 1.3m2 (13.99 sq. ft.) or for instance, 4’-8” x 3’-0”.

Door Dimensions
Room Minimum Width Minimum Height
Dwelling unit entrance, vestibule or entrance hall 810 mm 1980 mm
Stairs to a floor level that contains a finished space, All doors in at least one line of passage from the exterior to the basement, Utility rooms 810 mm 1980 mm
Walk in Closet 610 mm 1980 mm
Bathroom, water closet and shower room 610 mm 1980 mm
Rooms located off hallways permitted to be 710 mm wide 610 mm 1980 mm
Rooms not mentioned above and exterior balconies 760 mm 1980 mm
City of Kingston: Housing Guide (PDF)
Window Dimensions
Room Units less than 5 years old
No Electric Lighting Electric Lighting
Living room and dining room areas 10% of floor area 10% of area served
Kitchen area 10% of floor area Window not required
Bedrooms 5% of floor area 5% of area served
Laundry 4% of floor area Window not required
Bathrooms 0.37 m2 (4 sq. ft) Window not required
Basement egress window Unless a door at the same floor level provides access directly to the exterior, there must be a minimum of one window for egress that is:
  • Can open from the inside without the use of tools,
  • provides an individual, unobstructed open portion having a minimum area of 0.35 m2 (3.8 sq.ft) with no dimension less than 380mm (15”)
  • needs no support to keep it open
  • has 0.55 m (22”) outside clearance in front of the window
City of Kingston: Housing Guide (PDF)

How do I prepare my plumbing and septic for a secondary suite?

If you get your water from a private well and you waste goes to a private septic system, the secondary suite will need to use that as well. The problem this poses may be obvious—how do you know if your plumbing can support a second unit?

In the City of Kingston or County of Frontenac, you’ll need to contact a local septic installer to get your septic tank sized (they may have records of the original tank if you request them, but these are not always available). If you’re not in Kingston, your local health unit or building department may be able to help guide you.

Each secondary dwelling unit must have:

  1. Hot and cold water
  2. One bathroom sink, bathtub (or shower), and toilet
  3. One kitchen sink
  4. Access to laundry facilities (may be shared)
  5. Its own water shutoff valve

If your plumbing or your septic system is not able to support a secondary suite, you will need to upgrade your system. If you are on municipal water and sewer services, you will need to check with your local municipal building department for direction, as every city has different rules and regulations in their bylaws.

How to ensure fire safety in a secondary suite?

Well, we’ve covered some aspects of fire safety already, like ensuring your windows and doors are in compliance with the building code. And just like zoning and building permits, there’s so much to cover we couldn’t possibly do it all here, but let’s cover the basics for new homes.

Smoke and CO alarms in secondary suites in new homes:

In new homes, all smoke alarms must be hardwired, meaning they cannot be battery operated and must be interconnected within the suite. They must also be paired with a strobe light.

Carbon Monoxide alarms are required when there is a fuel-burning appliance in any suite in the dwelling—or if there’s an attached garage. These alarms must be mechanically fastened, hardwired, and interconnected within the suite.

Fire separations in secondary suites:

Fire separations, or fire partitions, are walls inside of a building that are used to delay the spread of fire. Their purpose is to provide occupants with time to vacate the premises as well as give firefighters time to arrive. In a secondary suite, fire separation is required between suites.

Requirement Units less than 5 years old
Fire separations 45 minute horizontal and vertical separation between units and exits including structural elements supporting fire rated assemblies
Wall assemblies around the furnace and other common areas (i.e. – public corridor, common laundry room) are to be 45 min fire rated
Exit enclosure is to be a 45 min fire rated separation
Dampers on ductwork penetrating a fire separation.
Fire stopping on any penetrations through a fire separation
Doors 20 minute fire rated doors between dwelling units with self-closing devices
Sound transmission Wall and floor assemblies separating dwelling units are to have a 50 STC
City of Kingston: Housing Guide (PDF)
Spatial separation for secondary suites:

Spatial separation refers to the distance between buildings on a property and the property line. The purpose of setting out these distances is to prevent the spread of fire between properties—a major issue in cities in the past. Spatial separation also needs to be considered between the primary dwelling and the secondary dwelling when your secondary dwelling is detached, sometimes referred to as a carriage house or granny pod.

Maximum Total Area of Exposing Building Face, m2
Maximum Aggregate Area of Glazed Openings, % of Exposing Building Face Area
Limiting Distance, m
< 1.2 1.2 1.5 2 2.5 3 4 6 8 10 12 16 20 25
10 0 8 12 21 33 55 96 100 - - - - - -
15 0 8 10 17 25 37 67 100 - - - - - -
20 0 8 10 15 21 30 53 100 - - - - - -
25 0 8 9 13 19 26 45 100 - - - - - -
30 0 7 9 12 17 23 39 88 100 - - - - -
40 0 7 8 11 15 20 32 69 100 - - - - -
50 0 7 8 10 14 18 28 57 100 - - - - -
100 0 7 8 9 11 13 18 34 56 84 100 - - -
Over 100 0 7 7 8 9 10 12 19 28 40 55 92 100 -
City of Kingston: Housing Guide (PDF)

What are the requirements for heating and ventilation in a secondary suite?

While it is permissible to share heating and ventilation between units, we highly recommend splitting up your ductwork. Splitting it up will allow each unit to control their temperature individually, which you will greatly appreciate once both dwellings are inhabited.

Do note, however, that if you decide to separate your ventilation system, you’ll be required to install a smoke detector that will automatically cut power when it’s activated. You may also be required to install dampers, but this is not always the case.

Ready to build your secondary suite?

We hope this guide has been helpful to you! If you have further questions, or you’re reading to start planning, you can contact us today!