Accessory Apartments

In Milton, accessory apartments are self-contained dwelling units created by converting part of an existing dwelling. They can also be constructed as part of a new dwelling.

Accessory apartments are also sometimes referred to as secondary suites, secondary units, basement apartments and accessory dwellings.

Follow the process outlined below to ensure that you meet all of the building permit requirements for your Accessory Apartment.

Is your property zoned for an Accessory Apartment?

Under the Zoning By-law, an Accessory Apartment must:

  • be located in a detached single family or semi-linked (attached below grade only) dwelling serviced by municipal water and wastewater services,
  • have 3 legal parking spaces on the property, and
  • be no larger than 85 m2 (915 ft2) in floor area.

General Zoning By-law requirements for your property can be obtained by contacting the Zoning Department at (905) 878-7252 ext.2329 or by reviewing the Town of Milton Zoning By-law.

Apply for your Building Permit

Complete building permit applications are accepted in person on the 2nd floor of Town Hall at 150 Mary St.  Building permit fees are payable by cash, cheque or debit at the time of application. Building permit fees include the review of drawings and all required inspections. 

Building permit applications require 2 types of submissions:

  1. Permit Application Forms
  2. Construction Drawings

Permit Application Forms 

1. Application for a Permit to Construct or Demolish - All sections of the form must be completed, including the full legal description (which can be found on your deed, tax assessment, survey, or is available from the public computer kiosk located on the main floor of Town Hall next to the Reception area).

2. Schedule 1 Designer Form  - This form is required when someone other than an Architect or Licensed Professional Engineer is taking responsibility for the design of the Accessory Apartment.

This other person would be either:

  • the homeowner taking legal responsibility for the design, provided they understand and are willing to take responsibility for the applicable requirements of the Ontario Building Code
  • OR 
  • a registered designer with a Building Code Identification Number (BCIN) qualified in House or Small Buildings.  Drawings that are prepared by a registered designer (as defined in the Ontario Building Code) must include:
    • The qualified designer's name
    • The qualified designer’s registration number
    • The qualification identification number of the qualified designer (Building Code Identification Number: BCIN)
    • The qualified designer's signature
    • The stamp or statement that the qualified designer has reviewed and taken responsibility for the design activities. 

3. Residential Development Charge Form - This form is completed by the property owner, including the legal description, assessment roll number, floor area, and number of bedrooms in the existing dwelling unit and proposed accessory apartment.

Construction Drawings

The following construction drawings are required for an Accessory Apartment: 

  1. Site Plan (Sample A-1)
  2. Existing Floor Layouts (Samples A-2, A-4, and A-6)
  3. Proposed Floor Layouts (Samples A-3 and A-5)
  4. Sections and Wall/Ceiling/Fire Separation Construction Details (Sample A-7)
  5. Elevations showing Accessory Apartment Entrance and Egress Window (Sample A-8 and A-9) 

Sample Drawings

Refer to the enclosed sample drawings for specific drawing requirements, including the number of copies of each drawing required. 

In addition, when exterior window or door openings are added/enlarged or the Accessory Apartment does not have a door on a floor with direct access to the exterior, please refer to information on Exterior Openings Building Permits or Basement Walkout Permits for additional requirements.

Drawing Submissions

  • Digital drawings are preferred, however paper submission is also accepted
  • Create 1 physical copy of the Site Plan or one digital copy.
  • Digital files must be in PDF format and generated directly from the software used to create them (AutoCAD, Softplan, Revit, etc.) using a PDF printer or converter (no scanned copies).
  • Digital PDF files must have the document properties/restrictions/security settings/permissions set to allow, “Printing” and “Adding Markups”.
  • Submit on CD, DVD, or USB flash drive in person at the time of building permit application.
  • All paper drawings must be submitted in black and white (min. 2 copies of all), drawn to an appropriate scale (min 3/16” = 1’ or metric equivalent), and clearly legible. Drawings in pencil shall be photocopied prior to submission, with the density adjusted so that all information is clear and legible.  All walls must be drawn as double lines (accurately showing wall thickness), and drawings must clearly differentiate between existing and proposed construction. Every page drawing shall include the project address and the designers information.

Book your Inspections

Typical Accessory Apartment inspections can include (depending on the scope of work):

  1. Framing
  2. Insulation & Air Barrier
  3. Underground Plumbing, Above Ground Plumbing and Final Plumbing
  4. Heating Rough-in and Final Heating
  5. Final Building

Inspections are booked online or by calling the Building Division at (905) 878-7252 ext. 2396.

Rates and Fees

  • Typical homeowner related permit fees see our Residential Permit fees page.
  • For the complete list of Building Permit fees see our Rates and Fees by-law page.
  • All fees are required at the time of Permit Application (acceptable forms of payment include, Cash, Debit or Cheque).
  • Other charges may also apply.