Feasibility Check

Horizontal Split

These are units built by splitting your house to create a new unit on one of the floors. This split could be in the attic or on another floor in your house. To register your unit legally, there are some specific requirements you will need to meet. The city refers residents to this Ontario website for a detailed guide for checking these requirements. Click here to learn more. Before you review the information provided by the Ontario website guide, check out our checklist below as a starting point to see if your home is a candidate for this kind of new suite.

Remember to verify all code requirements with your local code, or hire a professional to do this for you!

Spatial Requirements

Measure the Ceiling

>>Generally, if your new unit is in an attic or has sloped ceilings it needs at least 50% of the unit to have a ceiling height of 2.03 m (6’ 8”), (Do not include areas with low ceilings less than 1.4 m (4’ 7”) high in your calculation!)

If your second unit is not in the attic, generally, your unit must have a ceiling height of 2300mm over 75% of the floor area in a living room or space, dining room or space, or kitchen space with a minimum clear height of 2100mm

Verify the ceiling height requirements with your local building code.

Measure your 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  suite.

Are there Windows?

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

The size of windows you will need for a unit 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 your window is used for exiting you may need larger windows. 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 your house:

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.’

2) You can provide access to the exterior through a shared entryway.

This means units will share a ‘front door’ and have a small section of communal space from which they access each of their units.

Most Garages can be retrofit to have a direct exterior access. 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.

What Kind of Access do You Have?

>>Option 1 -  Separate Second Entry
This is 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 unit. These are often separated from the main floor living space.

>>Option 2 - Stair Close to an Entry
If you don’t have a separate entry, it is best if the stair is close to an entry door. You will need to build a wall to separate the new unit entry from the main floor unit.
>>Option 3 - Stair Far From an Entry
This option will require the most work. First check to make sure you can access the stair to the new unit 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

1) Check your existing electrical service on your electrical panel

Find your 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.

2) Use the chart below to calculate your existing electrical capacity (Coming Soon!)

3) Check how many units you can add based on your existing electrical capacity. (Coming Soon!)

Verify the level of electrical service you will need with a licenced 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 horizontal split rennovation these include:

- unit access
- unit egress
- fire and sounds separation
- new bathroom(s)
- new kitchens(s)

Case Study:

This horizontal split case study involves creating distinct living units by subdividing the existing structure of the house in the horizontal axis, typically at each floor level. Interior walls are added to create the necessary rooms within each unit and demising walls are added between units to create necessary fire separations. The project introduces new kitchens and bathrooms for each unit. Major considerations include plumbing, fire separation, and unit access.

Existing Floor Plans
Case Study Plans