Many homeowners assume building permits are only required for major additions or new houses. In reality, some of the most common home renovations in Ontario require permits — even when the work looks minor or purely interior.
These projects often fail inspections, resale reviews, or insurance checks not because they were done poorly, but because they were done without approval.
Below are five renovations that frequently catch homeowners off guard.
1. Finishing a Basement
Finishing a basement almost always requires a building permit.
Even when no bedrooms or bathrooms are added, basement work typically involves:
- framing and insulation
- electrical wiring
- heating and ventilation changes
- fire and smoke separation requirements
Basement renovations also trigger life-safety checks such as:
- minimum ceiling heights
- smoke and carbon monoxide alarms
- egress requirements in certain cases
Basement work is one of the most common areas where unpermitted construction is discovered later — often during resale or inspection.
2. Creating or Modifying a Secondary Suite
Any renovation that creates a separate dwelling unit requires a permit.
This includes adding or modifying:
- kitchens
- bathrooms
- bedrooms
- layouts that allow independent living
Permits are required regardless of whether the suite is:
- rented
- used for family
- or existed informally before
Secondary suites introduce additional requirements related to:
- smoke-tight separation
- alarms
- heating and ventilation
- dwelling unit separation
Without a permit, a suite cannot be considered legal — even if it appears complete.
3. Removing or Modifying Walls
Removing or modifying walls affects far more than structure.
Even when a wall is not load-bearing, changes can impact multiple Building Code requirements, including:
- Ventilation
Walls define air distribution. Removing them can leave rooms without required supply or return air. - Heating
Each habitable room must be adequately heated. Wall changes can eliminate registers or create poorly served spaces. - Natural Light and Egress
Bedrooms and living areas require compliant windows. Changing layouts can create rooms that no longer meet light or escape requirements. - Minimum Room Sizes
Altered layouts can unintentionally create rooms that do not meet minimum area or dimension requirements. - Fire and Smoke Separation
Walls may form part of required fire-resistance or smoke-tight assemblies. Altering them can break continuity and cause inspection failure.
Because wall changes affect life safety and habitability, permits are typically required — even when the wall “doesn’t look structural.”
4. Building or Altering a Deck
Decks are one of the most misunderstood permit areas in Ontario.
Permits are commonly required for:
- decks attached to a house
- elevated decks
- decks supporting guards or stairs
Inspection failures often involve:
- improper footings or piles
- posts not centered or properly secured
- inadequate guards or handrails
- insufficient clearance above grade
Deck issues are highly visible and frequently flagged during inspections or neighbour complaints.
5. Adding or Relocating Plumbing Fixtures
Adding or moving plumbing fixtures typically requires a permit.
This includes:
- new bathrooms
- relocated sinks or toilets
- added laundry connections
- changes to drainage or venting
Plumbing issues often remain hidden until inspection, where problems such as:
- improper venting
- S-traps
- missing cleanouts
- inaccessible shut-off valves
are discovered.
Plumbing permits protect both building safety and public health.
Why These Projects Cause Problems Later
Unpermitted renovations often surface:
- during inspections
- at time of sale
- during refinancing
- or after insurance claims
Consequences may include:
- stop-work orders
- mandatory exposure of finished work
- engineering reviews
- retroactive permits with added conditions
Fixing unpermitted work is usually more expensive than permitting it properly from the start.
Key Takeaway
If a renovation affects structure, safety, plumbing, ventilation, heating, or occupancy, assume a permit is required until confirmed otherwise.
Permits are not obstacles — they are protections.
Disclaimer: This article is for general educational purposes only. Building Code interpretation and enforcement may vary by municipality. Always confirm requirements with your local Authority Having Jurisdiction.