Feasibility Check

Basement Conversion

These are units built in the basement of an existing home. They are common in the Toronto area. To legally register a unit, there are some specific requirements. The city refers residents to this Ontario website for a detailed guide for checking the requirements. Before you review the information provided by the website guide, check out our checklist below as a starting point to see if your home is a candidate for a basement suite. Remember to verify all local code requirements or hire a professional to do this for you!

Spatial Requirements

Measure the ceiling

The minimum ceiling height for a basement unit is generally 1.95m (6’-4-3/4”)

Measure the ceiling to see if it meets this minimum. If not, it will be expensive to make this change to register your unit as a legal basement suite. (It is possible to increase the height of the basement by underpinning, a construction method where the soil beneath the basement’s foundation is excavated and the foundations are extended and reinforced to create a higher ceiling height. This is expensive! Verify the ceiling height requirements with your local building code.)

Are there windows?

Natural light is a necessity for housing. If your basement already has windows this is a plus!

The size of windows you will need depends on how big your unit is and what type of room you are in. Some windows may need to be used as an exit (more on this below!) The building code has minimum window sizes for different areas in your unit. These are generally:

  • Living room or dining room - 10% of floor area
  • Bedrooms - 5% of floor area
  • Laundry room, kitchen, bathroom - no windows required.

If a window is used for exiting you may need a larger window. Window wells are a great way to get extra light into the basement - check out our construction catalogue for more details. Verify the window size requirements with your local building code.

Getting in and out safely


There are two ways you can provide access to units within a house:

Option 1) You can provide direct exterior access. This means each unit has its own fire-separated exit path from the main space of the unit to the exterior. In this case, each unit will have its own exterior ‘front door.’

Option 2) You can provide access to the exterior through a shared entryway (and or stairwell depending on the number of units.) This means units will share a ‘front door’ and have a small section of communal space from which they access each unit.

What kind of access do you have

Option 1 - Walk-Out Basement
This is the best option. A door from inside the unit opens directly to the outside.
Option 2 - Separate Entry Above
This is also a good option because you will not have to do a lot of work to allow access to the unit. A door at the main level, often at the side of the house, accesses a stair directly to the basement. These are often separated from the main floor living space.

Option 3 - Stair Close to an Entry
If you don’t have a separate entry to your basement, it is best if the stair is close to an entry door. You will need to build a wall to separate the basement entry from the main floor unit
Option 4 - Stair Far From an Entry
This option will require the most work. First, check to make sure you can access the stairs to the basement without disrupting the living space on the main floor.

You may also need to provide a second exit through a window in your unit that is large enough for a person to get through and easily open without any tools.

Electric, Heating/Air, and Plumbing

Check your utilities

Check your electrical service

Step 1 - Check the existing electrical service on your electrical panel

Find the circuit box. Find the main cut-off switch—this is typically the biggest switch in the box. The cut-off switch often has the number of amps written on it. You will likely need a minimum of 100 amps.

Step 2 - Use the chart below to calculate the existing electrical capacity (Coming soon.)

Step 3 - Check how many units you can add based on the existing electrical capacity. (Coming soon.)

Verify the level of electrical service you will need with a licensed electrical engineer or electrician.

Cost considerations

Whenever you are deciding what type of unit to add, it is important to understand what are the major cost considerations. For a basement unit these are:

- underpinning
- unit access
- fire and sounds separation
- adding plumbing (trenching new lines is expensive!)

Case study:

This basement renovation case study involves creating a distinct living unit by separating the existing stairwell and side entrance from the main floor unit. Existing windows are retained, with the addition of window wells for emergency exiting from bedrooms. The project introduces a new kitchen and non-load-bearing partition walls to create bedrooms. Plumbing is optimized by retaining existing infrastructure, making only the necessary additions.

Existing Basement Plan
Case Study Plan

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