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Permit guideTorontoBuilding PermitsAdditions & Alterations

Small residential additions and interior alterations

You need a building permit for an addition or an interior alteration to a small residential building, such as a detached house, semi-detached house or townhouse.

From Toronto’s own pages, checked Oct 2026.

  1. Check whether you need a permit

    • A building permit is needed for an addition to a small residential building, such as a detached house, semi-detached house, or townhouse.
    • A building permit is needed for an interior alteration to a small residential building, such as a detached house, semi-detached house or townhouse.
    • A Residential Infill Construction Public Notice is required to be posted on the site of all new residential infill construction and demolition projects, including additions greater than 100 m² (≈ 1,076 sq ft).
  2. Only if your project is an interior alteration to a small residential building, such as a detached house, semi-detached house or townhouse

    Interior alterations only

    All drawings to be done on standardized sized sheets, drawn to scale, fully dimensioned, signed and dated.

    General Information

    • If a party wall is involved in your project a building permit must be issued for all the properties separated by the party wall(s).
    • Each application must be filed by the owner or his/her authorized agent of each property at the district Building Permit office for the properties.

    Floor Plans

    • Fully dimensioned, for each level showing existing and proposed uses of all spaces, including location of smoke alarms and carbon monoxide detectors and all plumbing fixtures.
    • Provide existing/proposed construction with foundation and exterior wall information, showing interior partitions and structural framing above.

    Sections

    • Cross section(s) to show existing/proposed building construction and specifications of all floor, wall and roof assemblies.
    • Provide footing and foundation wall details including height of exterior grade above basement floor.
    • Show floor to floor, floor to ceiling and overall building heights.
    • Detail stairs, landings, guards and handrails.

    Construction Details and Notes

    • Building materials and specifications of all wall, floor and roof assemblies with typical wall section and typical roof detail.
    • Provide guard details including connection detail.

    Site Plan required for Second Suites or New Openings

    Where the proposed alterations include a new second suite, or where new openings are proposed, a site plan is required showing:

    • Survey or site plan showing property lines, lot area, right-of-way or easements (referenced to a current survey)
    • Location of existing/proposed buildings with overall dimensions and include setback dimensions to property lines and adjacent buildings.
    • Summary of permitted and proposed zoning provisions to include lot area, building area (GFA), coverage, and grade elevations to confirm height.
    • Indicate dimensioned parking areas, driveways, hard & soft landscape treatments, accessory structures (sheds, decks, detached garages, etc).

    Mechanical (HVAC) and Plumbing Requirements (if Applicable)

    • If your project includes an HVAC elements please review the Residential Mechanical (HVAC) Guide for additional requirement
    • If your project includes a plumbing or drain and water-service elements, please submit a Plumbing Data Sheet (below) with your Building Permit application.
    • For one- and two-unit houses, no plans are required unless the project includes a reverse-sloping driveway.
    • If the project includes a reverse-sloped driveway, then drawings must be submitted showing details of the reverse-sloped driveway and drain plan.
    • All other residential plumbing and drain permit applications must include drawings showing the layout of plumbing and related fixtures on each floor level.

    Required Forms

    Apply Online

    • To submit an application for building permit for interior alterations, all required forms and documentation may be submitted through Toronto Building Online Services Application Submission.
    • Once the application has been submitted, it will be assessed by our intake staff. If any required documentation is missing or incorrectly submitted, the applicant will be notified and the missing or incorrectly submitted documentation will need to be re-submitted.
    • When submitting your application online, you will have the option to submit your related mechanical, plumbing and drain permits once you have submitted your building permit application.

    Fees

    Interior alterations (partitions, finishings, etc.) Fee (per m², unless otherwise stated)

    • Group C, E and F: $11.53 per m² (≈ $1.07 per sq ft), effective January 1, 2026
    • Residential Unit Fee: each new residential unit included in an application, $56.33/unit
  3. Only if your project includes underpinning of the foundation of an existing house

    Underpinning the foundation

    Underpinning is a method of increasing the depth of an existing foundation by constructing new footings beneath the existing footings. You apply for a Residential Underpinning permit.

    Am I in the Angle of Repose?

    • The angle of repose is the maximum angle (measured from the horizontal) where the soil will remain stable.
    • Disturbing the soil anywhere within the angle of repose could lead to soil failure and result in serious and difficult to repair consequences.

    When is an Engineer Required?

    • A foundation shall be designed and reviewed on-site by a Professional Engineer when it is constructed below the level of the footing of an adjacent building and within the angle of repose of the soil.
    • Your designs must be sealed by a Professional Engineer, your Engineer must sign the Commitment to General Reviews form, and the completed Commitment to General Reviews (including Part A to be completed by the Owner) must be submitted with your permit application.
    • In all circumstances of underpinning, whether the underpinning was required to be designed by a Professional Engineer or not, you will be required (at the minimum) to provide testing and reports by a Professional Engineer during the first and last stages of the construction in order to pass inspections.

    Site Plan

    • Survey or site plan showing property lines, lot area, right-of-way or easements (referenced to a current survey)
    • Location of existing/proposed buildings with overall dimensions and include setback dimensions to property lines and adjacent buildings.

    Basement / Foundation Plans for Underpinning

    • Provide existing/proposed construction with foundation and exterior wall information, showing locations of proposed underpinning, locations of any support columns and structural framing above
    • Show stages of proposed underpinning, numbered to show sequence of work, and indicate the lineal metres of underpinning work proposed.
    • Where applicable, show distance to foundations of adjacent buildings, including depth of the footings of the adjacent building. Where the proposed underpinned foundation is to be constructed below the level of the footings of the adjacent building and within the angle of repose of the soil, the underpinning and related construction must be designed by a Professional Engineer.

    Floor Plans

    • Fully dimensioned, for each level showing existing and proposed uses of all spaces, including location of smoke alarms and carbon monoxide detectors and all plumbing fixtures.
    • Provide existing/proposed construction with foundation and exterior wall information, showing interior partitions and structural framing above.

    Sections

    • Cross section(s) to show existing/proposed building construction and specifications of all floor, wall and roof assemblies.
    • Provide footing and foundation wall details including height of exterior grade above basement floor.
    • Show floor to floor, floor to ceiling and overall building heights.
    • Detail stairs, landings, guards and handrails.
    • Show the depth (amount) of underpinning proposed.

    Construction Details and Notes

    • Building materials and specifications of all wall, floor and roof assemblies with typical wall section and typical roof detail.
    • Provide guard details including connection detail.

    Required Forms

    Apply Online

    • You may now apply for a permit for a residential underpinning permit online using the Toronto Building Online Services Application Submission Tool.
    • A User Guide is available to support your submission.

    Fees

    • Underpinning: $12.37/linear metre

  4. Prepare your plans0 of 22

    All drawings to be drawn on standardized sized sheets, drawn to scale, fully dimensioned, signed and dated. If drawings were prepared by a qualified designer, drawings must include the designer’s name, registration number, qualification identification number, signature, and stamp/statement that the person has reviewed and taken responsibility for the design activities.

    You need an account to see these 22 items.It’s free. Use Sign in at the top of the page to create one, then tick the items off on any device and print them as a checklist.

  5. Complete the forms10

    Applications including drawings with the seal of a professional engineer must include a completed Assumption of Responsibility for Engineering Content Form.

  6. Submit your application

    • You may now apply for a permit for a small residential addition permit online using the Toronto Building Online Services Application Submission Tool.
    • This service allows applicants to see what documents are required and which outside approvals, if any, are applicable to the submission.
    • A User Guide is available to support your submission.
    • All drawings, reports, and forms, including the completed Application for a Permit to Construct or Demolish, must be provided in a PDF format.
    • Please do not include any personal information on your Building Plans (e.g., the homeowner’s name or phone number).
    • The AI-assisted Building Permit Application Pre-Check is a voluntary tool that helps identify potential issues before you submit your application.

  7. Pay the fee

    Fee (per m², unless otherwise stated):

    • Effective January 1, 2026
    • Single Family Dwellings, Semis, Townhouses, Duplexes, Live/Work Units: $18.56
    • Interior alterations (partitions, finishings, etc.) Group C, E and F: $11.53
    • Residential Unit Fee: each new residential unit included in an application, $56.33/unit
    • The permit fees shown above are shown as Service Index per square metre of proposed work, unless otherwise specified.
    • For full details of permit fee calculation and a complete list of fee rates, see the Building Permit Fees page.

Written from Toronto’s own pages as published on 20 October 2026. The municipality decides what a permit needs: confirm with it before you apply. Legal notice

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