This page outlines what ARUs are, where they’re allowed, and how you can plan, build and register for one. It includes zoning and building requirements, application steps, and helpful resources to guide you through the process. 

↓ What is an ARU?
↓ Planning your ARU (Eligibility, Zoning and Building requirements)
↓ Registering your ARU
↓ ARU inspections
↓ Frequently Asked Questions

What is an ARU?

An Additional Residential Unit (ARU), also called an Additional Dwelling Unit (ADU), is a self-contained living space located on the same property as a primary home. It can be:  

  • Inside the main house, for example, a basement apartment  

  • In a detached structure, for example, a tiny home or coach house  

ARUs are allowed in both urban and rural areas of Milton, provided they comply with zoning by-law requirements. 

Additional Residential Unite examples: Basement conversion, converted garage, attached ARU, detached ARU, attic conversion

Planning your ARU  

Considerations when planning your Additional Residential Unit (ARU), also called an Additional Dwelling Unit (ADU), project are outlined below. 

Eligible urban properties
ARUs are permitted in both urban and rural areas of Milton, provided they comply with zoning by-law requirements.  In the urban area, up to 3 ARUs are allowed on properties with municipal water and sewer connections that contain the following house types: 

  • Detached houses; 

  • Semi-detached houses; semi-link houses; and, townhouses (does not include stacked or back-to-back townhouses) 

Properties in the urban area that are zoned residential and contain one of the house types listed above that do not have municipal water and/or sewer connections are allowed to have up to 2 ARUs. 

ARUs may be located inside the house or within a detached building on the same lot but only one (1) ARU may be allowed in a detached building.  

 If your property is part of a condominium, check with your condo corporation to see if there are any restrictions on ARUs.
Eligible rural properties
In January 2026, Milton updated its Official Plan and Zoning By-law to allow ARUs in rural areas of Milton, where permitted by provincial policy, as follows:  

  • RV or C4 Zones outside of the Niagara Escarpment Plan Area: 

    • One ARU permitted in a detached house, semi-detached house, townhouse, or accessory building on the same lot.

  • RV or C4 Zones within the Niagara Escarpment Plan Area:  

    • One ARU allowed within a detached dwelling in the Escarpment Rural Area Designation only. 

    • Detached ARUs are not allowed. 

    • ARUs are not allowed on lots with more than 1 house or within a house that is currently being used for Shared Housing or a Bed and Breakfast Establishment.

  • A1, A2, or RE Zones within the Greenbelt Protected Countryside Area:  

    • One ARU inside the home or in an existing accessory building where located outside of the Greenbelt Natural Heritage System. 

  • A1 Zone outside of the Greenbelt Protected Countryside Area:  

    • Up to two ARUs per lot; only one can be in a detached accessory building. 

Zoning requirements 

Before adding an ARU in Milton, you need to follow local zoning and building rules. These rules cover things like size, location, and parking. Milton’s Zoning By-laws set the standards for ARUs. If your plan doesn’t meet these requirements, you may be able to apply for a minor variance to request an exception. 

Need help? Contact the Zoning Division at 905-878-7252 x2329. 

Building permits 

You’ll need a building permit to build an ARU. Hiring a qualified designer can make the process easier. 

What to include in your application: 

  • Site plan 

  •  Floor layouts (existing and proposed) Construction details for walls, ceilings, and fire safety 

  • Drawings showing entrances and windows  

For more details, visit the Government of Ontario’s guide on building a second unit. 

Need help? Contact the Building Division at 905-878-7252 x2397. 

Registering your ARU

All ARUs in Milton—new or existing—must be registered with the Town. Registration helps:  

  • Improve safety for residents and, first responders  

  • Ensure compliance with zoning by-laws, the Fire Code, and Building Code 

  •  Support legal, affordable housing options  

  • Enable faster emergency response 

Download the ARU Guide to learn more about the Town’s ARU program and registration requirements.to learn more about the Town’s ARU program and registration requirements. 

How to register your ARU

Step one: Submit your applicaton
Complete the ARU Registry application online or visit the Community Services Desk at Town Hall.  
Step two: Pay the registration fee
A registration fee of $340 per ARU will be required. Payments are able to be made either in person or by mail. Inspections will only be scheduled after payment is received.  

Pay in person:  

Please make your payment (cash, debit, or cheque payable to the Town of Milton) at the cashier’s desk at Milton Town Hall (150 Mary St.). After completing your payment, visit the Community Services counter to book your inspection.  

Hours of operation:  

Monday to Friday: 8:30 a.m. – 4:30 p.m.  

Closed Saturday, Sunday, and holidays.  

After-hours drop boxes are available at both the north and south entrances for cheque payments only.  

Pay by mail:  

Mail your cheque payable to:  

Town of Milton - 150 Mary St., Milton, ON, L9T 6Z5  

Please allow enough time for delivery and do not send cash by mail. Include your ARU address in the cheque memo. Once your payment has been processed, our team will contact you to schedule your inspection. 
Step three: Prepare for your inspection

A municipal law enforcement officer and a fire prevention officer will schedule a visit to your property to inspect the ARU. They’ll check that it meets:  

  • Zoning by-law requirements  

  • Safety standards  

  • The Fire Protection and Prevention Act
Step four: Receive your compliance certificate
If your ARU passes all inspections, it will be registered. You’ll receive a certificate of compliance by email. This certificate is valid for one year. To keep an ARU in good standing, homeowners must renew their compliance certificate online each year. During the pilot, there is no fee for renewing your ARU registration. Town staff will reach out to homeowners with instructions to renew. 

Register your ARU 

ARU inspections

Inspections are part of the Town’s ARU Registry Compliance Program and help ensure units meet safety and living standards. 

Inspections are scheduled at a time that works for both the property owner (applicant) and the tenant. Appointments are booked during the registration process and are available Monday to Friday during the day. Most inspections take about 30 minutes. 

The property owner or applicant must be on-site during the inspection. Inspectors must have access to the unit and all required areas. As part of the inspection, smoke alarms throughout the home will be tested to confirm compliance with the Fire Code. 

What inspectors check 

During an inspection, staff will: 

  • Confirm that smoke alarms are working and interconnected throughout the building. 

  • Ensure carbon monoxide (CO) alarms are installed and working on each level. 

  • Check that required fire separations are intact. 

  • Confirm the property meets the Town’s Property Standards By-law and other applicable by-laws. 

  • Ensure laneways and exterior access routes are clear and free of obstructions. 

  • Verify that sump pumps are accessible and not blocked by storage. 

  • Confirm furnace rooms are accessible, with clear and unobstructed entry. 

  • Provide education on fire safety and municipal requirements related to ARUs. 

Frequently Asked Questions

Why do I need to register my ARU? 

All ARUs (existing and new) must be registered, and there are no “grandfathering” exemptions. You can register your ARU online or in person at Town Hall.  

The ARU registration system was established to ensure that all ARUs in Milton are:  

  • Safe and legal  

  • Compliant with zoning by-laws  

  • Properly documented to support Fire and Rescue Services in an emergency response  

The registry plays a critical role in enhancing public safety, by-law compliance, and emergency response capabilities across Milton.  

Maintaining unregistered units compromises the safety of everyone in the home as well as the community. These units may face enforcement actions and even potential insurance consequences. Enforcement could include Fire Code violations, fines, and even legal action.

Do I need to register if my ARU is for family or not being rented?

Yes. All ARUs must be registered, regardless of who lives there. This ensures safety and emergency preparedness. 

If I have already paid a building permit fee, why do I need to pay a separate ARU registration fee? 
The building permit fee covers inspections and reviews during construction to ensure compliance with the Ontario Building Code. The ARU registration fee, on the other hand, supports ongoing enforcement, public safety, and emergency response readiness after construction is complete. 

Will the registration fee and inspection process be required yearly?

During the three-year pilot, ARU compliance certificates are valid for one year from the date they are issued. To keep an ARU in good standing, homeowners must renew their compliance certificate online each year before it expires. 

Staff will contact homeowners ahead of time with step-by-step instructions on how to complete the renewal. During the pilot, there is no fee for renewing your ARU registration.

How will my property taxes be affected? 

The Town of Milton does not assess property values. Homeowners are required to contact the Municipal Property Assessment Corporation (MPAC) to determine how property taxes will be affected. 

Does an ARU need its own house number? 

No. An additional residential unit does not receive a separate municipal house number. The property keeps one civic address. Each unit on the property, including an ARU, is identified using a unit or suite number (for example, 123-1 Main St.). 

Property owners are responsible for ensuring the civic address number is clearly visible from the street, so emergency services, delivery drivers and visitors can easily find the property. Address number signs must meet the Town’s size, placement and visibility requirements. 

Learn more about municipal address number sign requirements.

Does the Town of Milton handle landlord‑tenant disputes? 

No. The Town of Milton does not get involved in landlord‑tenant disputes. This includes issues such as rent, maintenance concerns, or evictions. These matters fall under provincial jurisdiction and are managed by the Landlord and Tenant Board (LTB). 

For help, guidance or to file a complaint, visit the Landlord and Tenant Board. 

I am a tenant living in an ARU. Do I have to let Town inspectors into my unit? 

Yes, Town inspectors must be allowed to enter the unit to complete a safety and property standards inspection. 

Inspections are scheduled at a time that works for both the property owner (or applicant) and the tenant. The visit usually takes about 30 minutes and focuses only on areas needed to confirm the unit meets safety, fire, and property standards. 

During the inspection, staff may check items such as smoke and carbon monoxide alarms, fire separations, clear access routes, and other required safety features.