Additional Dwelling Units

Additional Dwelling Units (ADU) are a self-contained residential units within a main dwelling (ie. single, semi, townhome dwelling unit) or within a detached building or structure on the same lot as the main dwelling (ie. within a detached garage).

Where permitted, ADUs - also referred to as an in-law suite or garden suite- can be constructed to provide long term rental accommodations for independent family members, friends and people of all demographics. ADUs also make more efficient use of existing infrastructure and the housing stock, and are a great way to generate rental income to assist with the cost of home ownership.

Illustration of various forms of second dwelling units including as units within building or units within accessory structures.

Where are ADUs permitted?

ADUs are permitted within a single, semi, or town home dwelling unit in Agricultural and select Residential zoning districts.
ADUs are also permitted in a detached building or structure accessory to a main dwelling (such as within a detached garage or garden suite constructed for such purpose) in Agricultural and select Residential zoning districts.
An ADU is not permitted in a mobile home or residential zoning districts permitting exclusively three (3) season occupancy.
An ADU is not permitted within a required front, side, or rear yard.

Land Use Policy and Zoning Regulations

Generally, three (3) dwelling units (Main dwelling and 2 ADUs) are permitted on a residential lot in an area of settlement where servicing is available.
Two (2) ADUs may be permitted within the main dwelling or one (1) ADU may be permitted within a main dwelling and one (1) ADU may be permitted within a detached structure.
In an Agricultural Area, one (1) additional dwelling unit is permitted.
ADUs cannot be severed from a lot to create a new and separate lot.
The Gross Floor Area (GFA) of the ADU cannot exceed the GFA of the main dwelling.
The Gross Floor Area (GFA) of the ADU within an attached garage cannot exceed the GFA of the main dwelling.
In a settlement area, ADUs are limited to one (1) storey in height in a residential district.
An ADU in an Agricultural area is not limited to one (1) storey in height.
One (1) onsite (ie. off-street) parking space is required for each ADU.
A separate service connection will not be permitted to service an ADU.
An ADU cannot be used in whole or in part as a short term rental.
Tiny homes, which are not a defined term in the Ontario Building Code or the Town’s Zoning By-law, can be considered an ADU.
A motor home, recreational vehicle, or trailer is not considered an ADU.

A building permit is required for the addition or construction of an ADU, and will be required for the conversion of ADUs within the main building (for example, basement or attic suites), and/or accessory structures (detached garages).

FREQUENTLY ASKED QUESTIONS ABOUT ADUs

Do I Need a Building Permit for an Additional Dwelling Unit (ADU)?

Yes — a Building Permit is required before you start building an ADU.

This includes submitting a complete application with:

Required drawings and documents
Compliance with the Ontario Building Code
Payment of the permit fee

What Is an Additional Dwelling Unit (ADU)?

An ADU is a self-contained living space with its own kitchen, bathroom, and sleeping area. It can be:

Inside your existing home (e.g., in a basement or attic), or
Detached, as a separate building on your property (e.g., garden suite)

What Does the Ontario Building Code Require?

The Building Code sets minimum standards to ensure your ADU is safe and livable. Requirements may differ based on whether your ADU is inside your house or in a separate building.

ADUs Inside the House

Here are some key requirements:

House Age – Different rules may apply depending on how old your home is.
Water Service – You may need to upgrade your water line if the plumbing load increases.
Location in the House – ADUs can be on any level, but rules vary for basements, attics, or upper floors.
Room Sizes – There are minimum sizes depending on layout (open concept or with walls).
Ceiling Heights – Minimum height is required, especially in basements and attics.
Windows – Must be included in living spaces. Size depends on the room’s purpose.
Safe Exits – Must have safe ways to exit in case of emergency.
Plumbing – Requires hot and cold water, a sink, toilet, shower or bathtub, kitchen sink, and laundry access (in-unit or shared).
Smoke Alarms – Must meet CAN/ULC S531, include a flashing light, and be properly labeled.
Carbon Monoxide Detectors – Required if you have a gas/propane furnace or an attached garage. Can be battery or electric.
Heating and Ventilation – Shared furnaces are allowed, but you must install a smoke detector in the ductwork that can shut off the furnace in case of smoke.
Fire Separation – Fire-resistant construction is required between the ADU and the rest of the house.
Septic System (if applicable) – Must have enough capacity to support the added use.

Detached ADUs (Garden Suites, Coach Houses)

Requirements for detached units include:

Water Service – May need to be upgraded depending on total usage.
Fire Department Access – Must be a clear path from the street at least 1 metre wide and 2.1 metres high.
Footings and Foundations – Must follow Building Code standards.
Room Sizes and Ceiling Heights – Must meet minimum requirements.
Windows – Must meet size rules based on room use. Limits may apply based on how close the wall is to property lines or other buildings.
Safe Exit – Requires a direct exit to the outside.
Plumbing – Requires a full kitchen, bathroom, and laundry access.
Smoke Alarms – Must meet CAN/ULC S531, be hardwired and interconnected, and include a flashing light.
Carbon Monoxide Detectors – Required if there’s a fuel-burning furnace or an attached garage. Must be hardwired.
Heating and Ventilation – Must follow Building Code and include an HVAC design by a qualified professional.

What Do I Need to Submit for a Building Permit?

To apply, you must submit:

A building permit application form
The application fee
Two sets of construction drawings by a licensed designer

Drawings must include:

Site plan
Foundation plan
Floor plans
Building elevations
Cross sections and construction details
Engineered drawings (if needed)

Apply Online with Cloudpermit

The Town of Essex uses Cloudpermit, an easy-to-use online system. With Cloudpermit, you can:

Apply for building permits 24/7 from your phone, tablet, or computer
Track your application and receive updates automatically
Book or cancel inspections
Communicate directly with staff
Pay online using a credit card
Submit changes to your permit if needed.

Do ADUs affect my property taxes?

MPAC assesses additional dwelling units (ADUs) in Ontario by including them in the overall property assessment, just like any other structure on the property. This means the value of the ADU is factored into the total assessed value, which in turn affects the property taxes. Generally, an increase in assessment leads to an increase in property taxes. For further information on your assessment please reach out to MPAC at 1 866 296-6722

You may be eligible for an GST/HST rebate on the construction of your ADU. Please see GST/HST New Housing Rebate - Canada.ca for the criteria. We recommend consulting a public accountant or CRA if you have further questions.

Are Development Charges and Parkland Fees applicable?

No, Additional Dwelling Units are exempt from all Development Charges and

Parkland Fees.

Getting Started

Not sure if your lot is eligible for an ADU and what models would work best? The Town of Essex makes it easy with the online mapping tool!

Searching your property is simple:

Visit the Online Mapping Tool.
Click the arrow on the left of the screen to expand the menu.
Click the check box titled 'Additional Dwelling Units' to activate the layer.
To find the desired property, click the 'Tools' icon in the upper right hand corner of the screen. Click the 'Custom Search' tab. Click 'Search Address' and enter the desired address.
To review the site suitability, right click over the desired property on the map, click 'Find Data on the Map', and click 'ADU Suitability' from the menu on the left hand side of the page.

A screenshot of the ADU mapping tool webpage.

Search Your Property

Property Categories

The legend for the ADU Search mapping tool.

Yellow: Suitable for Internal/Attached
A Yellow Lot means that the property does not meet the requirements to build a detached additional unit, but meets the general requirements to construct or add an internal unit into the primary dwelling.

Red: Not Suitable
A Red Lot means that the property does not meet the fundamental requirements to add an additional unit. This is most often a zoning, floodplain, or primary dwelling issue.

Light Green: Potentially Suitable
A Light Green Lot means the property meets almost all of the requirements to add a detached unit, but there are some site specific constraints that the mapping tool cannot account for such as unique flood permits from the conservation authority, meeting proper fire safety regulations, or mature neighbourhood requirements in terms of unit design and placement.

Hatched Green: Suitable
A Hatched Green Lot means that the property meets all requirements to add a detached unit, and the mapping tool cannot find any additional requirements that may heavily impact the suitability of the project.

Contact us

Planning Department

For more information on Land Use Policy and Zoning Regulations regarding ADUs in the Town of Essex, please contact the Planning Department at essexplanning@essex.ca or 519.776.7336 ext. 1128.

Building Department

For more information on applying for a building permit, permit fees and timelines please contact the Building Division at buildingdept@essex.ca or 519.776.7336 ext. 1400.