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First of all, the article you are reading is extracted from Ontario Building Code form Ontario.ca website. If you want to access to the full documetn, please click here.
Disclaimer: This article if provided for the guide to give you the basic idea, and it is not a construction, engineering, architectural, or legal advice. If you want to do renovation and building, you shoud refer to your city.
A duplex is an appartment in a house which needs to be separated horizontally from other floors of the house.It is legal when you have the permit and consider all the necessary regulations to renovate or build it in your house. A second unit is a self-contained dewlling unit which has its own private kitchen, bathroom, and sleeping areas.
How can I Convert my house to a legal duplex
It is a good idea to have a second unit to make privacy for a family member for an independent life, or to rent it to a tenant and make some money to pay off the mortgage or make extra income. But you need to do it in the right way and consider all you need before renovating, or constructing anything. There are a number of questions you need to answer to see if you can get the permit to add a secondary units. What is type of your house. Is it detached or semi-detached? Is your house age less than five years? Do you want to renovate your house to add the secondary unit? This is going to be a good check list for you before your decision to convert your house to a legal duplex.
*For the houses less than 5 years old of age different rules are considered which is explained in another article based on City of Kingston guide*
Some of important things to do before adding second unit is ot prepare:
Whatever you do, it is crucial to meet the Ontario Building Code regulations, which will be shown in the design and drawings we will provide for you. This is because safety to protect residents, and privacy are so important to provide a healthy place to live. Because the drawings and plans are so complicated, our architects will help you to provide with the essensial drawings to get the permits. We can become your agent in all steps of your project to deal with necessary approvals including building permits, inspections, and certified professionals.
There are some minimum Building Code regulations that you need to consider for any secondary unit in a legal duplex. You may also need to do some more things further than minimum regulations if it’s needed by local municipality. This s not only for the safety, but it also provides homeowners standards and advantages to provide occupants a better and nicer place to live in the second unit. Here the most important factors to consider are mentioned.
Depending on how old is your house build different regulations should be considered for second unit. If your house is more than 5 years old, Building Code is more flexible to do renovations for your house. The houses more than 5 years old age are classified as existed house. The less age means the house is classified as a new building and should meet new construction building regulations that should be asked from local building department.
| Age of the house | More than 5 years | Less than 5 years |
| Classifications | Exsisting house | New building |
| Regulations | Building Code is more flexible for renovation | must meet new construction requirements |
If you want to build or renovate your house for a second unit, it can be on any floor or multiple floors. Mostly the second units are build on Attic or Basement. Base on the regulations in Ontario Building Code, the location of the secont unit may be different. Here are two images that can make it clearer for you the location of the second unit.
Second Unit ofa duplex house. The image was taken from Ontario Building Guide
The sizes of the rooms of a dwelling units house including secont unit are in Ontario Building Code. Depends on the room separated by walls or by open concepts, the size of a room varies. Take dining room as an example. If it’s separated by walls, the minumum size of the room should be 7 m2 (75 ft2), while if you use open concept bachelor unit with sleeping, living, and dining areas, and kitchen space all combined is permitted to be 13.5 m2 (145 ft2). The chart below gives a good information of minumum required area for different spaces in the house.
| Room/Space: | required area (m2) | required area (ft2) |
| Living area | 13.5 | 145 |
| Dining area | 7 | 75 |
| Combined living, dining, and kitchen area in a one bedroom unit | 11 | 118.4 |
| Master bedroom (without building closet) | 9.8 | 95 |
| Other bedrooms (without building closet) | 7 | 75 |
| Bathroom | sufficient space for sink, toilet and shower stall or bath | |
| Combined sleeping, living, and dining areas and kitchen space | 13.5 | 145 |
| (Relevant Building Code provisions – Division B, Subsections 9.5.4. to 9.5.9.) | ||
Here there is a schematic of how to measure the rooms.
minimum required area for second unit
Mostly homeowners like to make the attic floor or the basement as their second unit. Before choosing which unit to renovate it is to important to measure the height of the ceiling if it’s possible to use it as the second unit. For different parts of the house, minimum ceiling height is different.
So for the attic, first you need to ignore the areas with a ceiling height less than 1.4 m, and work on the other parts to divide it into %50 percent of 2.03 m(6′ 8″) and %50 of this height to lower height of 1.4 m (4′ 7″).
(Relevant Building Code provisions – Division B, Table 11.5.1.1.C., Compliance Alternative 102)
Ceiling height for second unit in a legal duplex
In a second unit, considering windows is one of the requirements. The size of the windows can be calculated based on the size of the unit. Since the size of the windows is proportional to size of the unit, Larger places need to have bigger windows. windows sizes are a percentage of the rooms. Some windows can also be used as a way of exit that is explained in the EXITS part of this guide.
Here in the chart below, minimum size of the windows are brought when they are not going to be used as the exit:
| Room/Space: | Minimum Required Windows Area: |
| Living and Dining Room | 5% of the floor area |
| Bedrooms | 2.5% of the floor area |
| Laundry room, Kitchen, Bathroom | windows not required |
Second unit should have all the separate requirements to meet anything necessary for bathroom, kitchen and laundry. Here the requirements are listed below:
For doing all the plumbing you need a qualified plumber
(refer to Building Code, Division B, Articles 9.31.4.1 to 9.31.4.3 for relevant regulations)
Second unit should be independent of other parts of the house when doing plumbing repairs, so shut-off valves should be considered whenever it’s needed to deliver service without affecting water flow in the other parts of the house.
(refer to Building Code, Division B, Sentences 7.6.1.4 (2) and 7.6.1.6.(1))
Sometimes a house is located in a place that the house is subject to flooding or sewer backup. In this case, a backwater valve is needed to help preventing sewage in municipal drain pipes from entering floor drains and plumbing fixtures.
(refer to Building Code provisions- Division B, article 7.4.6.4)
A septic system in a second unit is permitted as long as the septic system has the capacity to handle the increase in sewage. For this, you need to check with building department in City of Kingston to see of the septic system size is right. If not, an upgrade for the septic system is needed for a safe treat the extra sewage flow
refer to Building Code provisions, Division B, Sentence 11.4.2.5 (4)
Some municipalities rely on regional health units or conservation authorities to enforce the septic system requirements of the Building Code. In this case you need to contact to local building department to advise you if that’s the case.
As Building Code says, for a second unit it’s allowd to have a single furnace with an air ducts system in common. For fire safety it is necesseray to use a special type of smoke detector in the main supply or return air ducts. This special type of smoke when activated, will turn off the fuel supply and electrical power to the furnace causing it to shut down and preventing the spread of smoke from on unit to the other.
Duct-Type Smoke Detector should meet a specific performance standard known as UL268A. You need a qualified contractor to make sure that the right type of the detector is installed properly.
refer to Building Code provisions, Division B, Table 11.5.1.1 C., Compliance alternative 195)
For Kitchen and Bathroom in the second unit, ventilation is also required. The ventilation can be provided by a ceiling exhoust fan, or a window that opens to outside.
refer to Building Code provisions, Division B, Article 9.32.1.2. as modified by Table 11.5.1.1.C, Complicance Alternative 194
While one furnace and air duct is OK to heat an entire house, it is suggested to use a second furncae and air duct when adding a second unit. Having one system in common sometimes cause the cooking smells, recreational smoke and other odours, as well as noise to transfer to other unit. In addition having one thermostat in the whole house may be an issue to residents when the pleasant tempreture for one of the units is not good for the other one.
Building Code requires you to ensure adequate lighting in rooms and spaces in the second unit. So second unit must have:
refer to Building Code provisions – Division B, Article 9.34.2.2. and 9.34.2.3.
Better to hire a licensed electrical contractor to do the work. The licensed elecrician can also get electrical permit and arrange inspections for you.
Fire safety
For fire safety, the second unit will need a fire separation from rest of the house. This fire separation actually works as a physical barrier to slow the spread of the fire from one part of the house to the other. The fire separation must be continuous and include protected openings if necessay (e.g fire dampers) in order to work prpoerly.
A fire separation can be a wall, door, or floor and ceiling, with a self closing device, or a combination of those things. It can be built using typical building materials such as lumber and drywall. For example, a 30 minute fire separation can be built using 38 mm* 89 mm (2″ *4″) wood studs, 13 mm (1/2″) thick drywall on both sides and fibre-type insulation between the studs. Lath and plaster construction typically found in older houses is an example of a 15 min fire separation.
| For adding a second unit it is required to have 30 min fire separation between units and between units and common areas based on the Building Code. When you renovate a house to add a second unit, if you need for floor and ceiling alteration, you should make sure that it become a 30 minute fire separation as you can see for the floor and ceiling diagram |  Smoke alarm and Carbon Monoxide alarm location |
A fire separation can be reduced to 15 minutes if the entire house has interconnected smoke alarms.
| Good-to-know: a wall built for fire separation requirements will help to reduce the noise between units too. A fire sepration wall is shown in the wall fire separation diagram |  30 minutes wall fire separation |
For preventing or stopping any fire incident from anything to initiate it, smoke alarms can work well. These smoke alarms which are also know as smoke detectors, should be installed in the seceond unit and they must have CAN/ULC S531 performance standard to meet the minimum quality to meet the Ontario Building Code. There is always a label on the alarm that ensures the homeowners to install the right one for the second unit. These smoke alarms, which you may have seen them before, must also have flashing light when they become activated. Smoke alarms are widely available in hardware and home renovation stores, so you won’t have any problem to find them.
Better to do: To have a higher safety of your second unit, it is suggested to install smoke alarms in strorage rooms and service areas that are interconnected with smoke alarms in the second unit. Fires in remote places of a house are often the most deadly as they are longer burn to be detected by smoke alarms.
It is very important to place the smoke alarms. The must be located :
refer to Building Code Provisions, Division B, Subsection 9.10.19.
Carbon monoxide is a product of natural gas and other similar fuels burning in a furnace. If you have a furnace that uses furnace which consumes natural gas, propane or other similar fuels you may need to use carbon monoxide alarms. If your house has an attached garage, carbon monoxide alarms are needed.
Carbon monoxide alarms can be operated with battery or electrical power, and they must be located:
Near bathroom or sleeping areas in the second unit
In the furnace room, if the furnace room is a separtae space from the residential units
refer to Building Code Provisions, Division B, Articles 9.33.4.1. and 9.33.4.2. as modified by Table11.5.1.1.C., Compliance Alternative 197
Smoke alarm and Carbon Monoxide alarm location
Exits
Second unit should have safe exits. The rules for exits are different for second unit and it depends on the location of the second unit in the house. it is preferred that the second unit to have a separate exit. If it’s not possible to consider a separate exit:
How much does it cost to build a legal duplex
Can I rent a basement in my legal duplex?
What is the first step to transform my house to a legal duplex?
How long does it take to finish the house?
Here in SAMandREZ we provide you all the permit drawings, and we are beside you in all the steps from design, permits, and building. We provide you high quality services with licensed and reliable people who are skilled enough to make you happy of your renovaion projects.
