Feasibility Check

Horizontal Addition & Split

These units are created by combining two methods of unit creation: addition and horizontal split. By adding a new addition to the rear or side of the existing building, and subdividing the floors into self-contained dwellings, you can create more living space within the home and add new units. The checklist below provides some key items you should consider before selecting this type of multiplex. Remember to verify all code requirements with your local code, or hire a professional to do this for you!

Spatial Requirements

Check to make sure you have room for an addition

Look up your property
Side and rear yard setbacks are specific to different neighbourhood zones. You can look up your property’s specific zoning regulations using this map.Here’s a video that explains how to use the city’s  map website. If you have trouble navigating, ask a professional for help!

Check the rear yard setback
Once you locate the property on the zoning map, you can find a link to the zoning rules for the property. This will tell you the allowable setbacks and other regulations. You can also use a measure tool to check the size of the building or other dimensions.

Check if you have space for a rear addition
Make sure you have enough space in your backyard to add a unit to the back of your home.

  • measure the distance from the back of your home to your rear property line
  • check the zoning code (here) for the required rear yard setback
  • subtract the allowable setback from the backyard dimension
  • if the result is less than 3m, consider another option for adding a unit

Check if you have a ‘deep’ lot.
If you have a deep lot, you are allowed to have a 19m deep building, if not, you are allowed to have a 17m deep building. A deep lot is defined as: at least 36m deep where the lot is less than 10m wide, or at least 40m deep where the lot is more than 10m wide.

Check if there’s room to add a rear unit.
After you determine the max allowable, building depth, either 17m or 19m, measure the depth of your existing home. Subtract the depth of the home from the allowable building depth to see how much space there is to build.
There’s no required depth for a separate unit, but most  are at least 3m deep, though some micro units can be 2.5m or even 2m deep.

Check for protected trees

  • Are you in an area protected by the  Ravine and Natural Features By-law? Check here.
  • Are there any trees over 30cm in diameter?

If your answer is yes to either of these questions, your trees require protection. Look up the required dimension for the required Tree Protection Zone around each trees New construction should stay out of this zone, otherwise you will need to apply for a permit to injure or remove your tree.You can find more information on tree protection zones, and permits for injuring or removing trees on the city’s website.

Want to add a garden suite or laneway suite now or in the future?

Measure the distance from the back of the house to the back of the lot.

Remember you need to maintain a space between a garden or laneway suite and the back of the house. You will need 5m for a one storey suite or 7.5m for a two storey suite.

You will also need to check the required rear yard setback for the laneway suite. Subtract these setbacks from that number to check if you have enough space. In order to have a viable depth for a new unit, you need at least 3m of space for a suite.



Can you put in windows?

Natural light is a necessity for housing.

If your addition will block windows in the existing house, you may need to add new windows to replace them.

We recommend making sure at least 2 sides of the addition are at least 1.2m form the property line. This will make it easy for you to add windows. If your wall is closer to the property line, adding windows requires additional fire protection (like sprinklers or fire shutters) which can be expensive!

Getting in and out safely


There are two ways you can provide access to units within your 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 the units.

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

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 an Addition & Split renovation this includes:

- unit egress
- fire and sounds separation
- new bathroom(s)
- new kitchen(s)
- site work
- new construction

Case study

The Horizontal Addition & Split case study involves creating distinct living units by subdividing the existing structure of a house in the horizontal axis AND adding an addition to the rear of the existing home. 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 Floor Plans

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