Decks
Check size / scopeSt. Catharines states that decks more than 600 mm above ground require a building permit. Lower or exact-boundary decks still require project-specific confirmation.
St. Catharines, ON
Building permits in St. Catharines
St. Catharines says permits are generally needed to erect, install, extend, alter or repair a building.
Official sources checked Sep. 24, 2026
Permit rules by project
Pick the project that matches your work. These are starting rules for St. Catharines; property-specific zoning, heritage and trade approvals can still apply.
Sheds & accessory buildings
Check size / scopeSt. Catharines states that accessory buildings such as sheds more than 15 m² require a building permit; smaller or exactly 15 m² structures still require zoning and scope confirmation.
Basement renovations
Permit requiredSt. Catharines explicitly lists finishing basements among home-renovation projects that require a building permit.
Secondary suites & ADUs
Permit requiredSt. Catharines accepts residential alteration permit applications for adding a secondary suite, and its current ADU program states that building permits are mandatory for ADU projects.
Home additions
Permit requiredSt. Catharines explicitly lists additions among projects requiring a building permit.
Interior alterations
Depends on scopeSt. Catharines requires permits for specified interior alterations such as enlarging openings and adding/removing walls; simple cosmetic work is not treated as a blanket permit project.
Walls / structural work
Permit requiredSt. Catharines explicitly lists structural alterations and adding/removing walls among permit-required work.
Pools / hot tubs
Permit requiredSt. Catharines explicitly lists swimming pools, hot tubs, ponds and related enclosures among projects requiring a building permit.
Garages / carports
Permit requiredSt. Catharines explicitly lists attached and detached garages and carports among projects requiring a building permit.
Plumbing / HVAC
Permit requiredSt. Catharines explicitly lists installation or alteration of plumbing and HVAC systems among projects requiring a building permit.
Fences
Confirm with citySt. Catharines’ current permit material clearly covers pool/fence enclosures, but the City does not publish one clear building-permit answer for every ordinary residential fence. Confirm fence/bylaw and pool-enclosure rules for the property.
Retaining walls
Permit requiredSt. Catharines explicitly lists retaining walls among construction projects requiring a building permit.
Demolition
Depends on scopeSt. Catharines requires a demolition permit to demolish all or part of any structure greater than 10 m². Smaller demolition scopes require confirmation.
Apply or ask St. Catharines
Use the municipality’s permit office for current forms, fees, drawings and questions about your property.
St. Catharines Planning & Building Services
- Address
- 50 Church Street, PO Box 3012, St. Catharines, ON L2R 7C2
Your application route
Open the official permit page ↗Use the official permit page to confirm project requirements, forms, fees and the current application process.
Good to know in St. Catharines
- The city lists additions, finished basements, wall changes, structural alterations, decks over 600 mm above grade, plumbing or HVAC alterations and accessory buildings over 15 m² among permit examples.
- St. Catharines lists decks more than 600 mm above ground and sheds over 15 m² among projects requiring a building permit, along with additions, basement finishing and structural alterations.
- In Ontario, the municipal building permit sits within the provincial building-code system, but zoning, conservation, heritage, utilities and some trade approvals can still require separate checks.
Official sources
Use these official links to confirm the current rule for your St. Catharines property.
View 2 official sources
Sources checked Sep. 24, 2026. Requirements can change; the municipality makes the final permit decision.
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