What triggers a permit
The City of Ottawa publishes a list of work that needs a building permit and work that does not, and bathrooms sit on both sides of it. Needing a permit: alterations, additions or extensions to a plumbing system, with replacing existing fixtures given as the exception; adding or removing walls, meaning creating different room sizes or uses; and interior structural alterations.
Not needing one: replacing kitchen or bathroom cabinets, provided plumbing fixtures remain in the same location; new flooring; and painting and decorating.
Read together, that puts the boundary at the drain. New tub, new toilet, new vanity, new tile, new paint, all in the existing positions, is generally exempt. Move a fixture, add a fixture, open a wall, and you are in permit territory with inspections at rough-in.
One thing to be clear about: a permit is a protection rather than a penalty. An inspector looking at a rough-in before it is closed up is a free second opinion on work you will never see again, and unpermitted plumbing alterations surface later, usually during a sale.
The ventilation provisions, and the defect they exist to prevent
The current code is the 2024 Building Code, O. Reg. 163/24, in force since 1 January 2025. Its Part 9 ventilation provisions set a principal exhaust fan capacity by bedroom count: 15 litres per second for a one-bedroom dwelling, 22.5 for two, 30 for three, 37.5 for four and 45 for five, with larger dwellings referred elsewhere in the Code. Supplemental exhaust must then be installed as necessary so that the total capacity of all kitchen, bathroom, water closet room and other supplemental exhaust reaches the required total ventilation capacity minus the principal fan capacity.
The practical point for a homeowner is simpler than the arithmetic. A bathroom needs real mechanical exhaust, sized for the duct run it actually has rather than for the number on the box, and it needs to discharge outdoors.
The defect this exists to prevent is everywhere in Ottawa. A fan ducted into the attic, or into a soffit that feeds the attic intake vents, pushes warm humid air into a space that sits below freezing for four months. It condenses on the underside of the sheathing, freezes, and then melts in a thaw. Attic frost, stained sheathing and mould in an Ottawa attic very often trace back to a bathroom fan. Insulated duct through cold space, a short run to an exterior wall or roof, a proper hood and a working damper. None of it is expensive at renovation time.
What the Code says about waterproofing, and why it is a floor rather than a target
Two provisions. Article 9.29.10.4 requires that ceramic and plastic tile installed on walls around bathtubs or showers be applied over moisture resistant backing. Article 9.29.10.5 requires that the joints between wall tiles and a bathtub or shower be suitably caulked with material conforming to CAN/CGSB-19.22-M, the standard for mildew resistant sealing compound for tubs and tile.
Those are minimums, and a custom tiled shower built only to them will not last. Current good practice adds a continuous waterproofing membrane, either sheet or liquid-applied, using one manufacturer's complete system including its own corners, seam tape, pipe seals and drain flange. Then a sloped pan, either pre-formed or a site-built mortar bed at roughly 2 per cent fall, with the drain integrated into the membrane rather than sealed to the tile.
Then the step that costs nothing and is skipped most: plug the drain, fill the pan, leave it 24 hours, and look at the ceiling below. Ask for the flood test in the contract. Once the tile is in, nobody can test anything, and a shower pan that leaks takes the ceiling under it with it.
The three things demolition finds most often in Ottawa
First, the fan ducted into the attic, or no fan at all in a pre-1970 bathroom where an openable window satisfied the code of the day. Fix it properly while the ceiling is open.
Second, green board or plaster behind shower tile with no membrane. Moisture resistant paper-faced drywall handles bathroom humidity, and it is not a waterproofing layer inside a shower enclosure. Finding it is normal in Ottawa housing from the 1970s through the 1990s and it explains a great many soft spots and stained ceilings.
Third, the exterior wall with no air or vapour control behind the tile. A shower on an exterior wall in this climate drives warm moist air toward a cold cavity all winter. Where that air can pass the tile assembly it condenses in the insulation. The correct detail on an exterior wall is worth asking about specifically, because a waterproofing membrane is itself a vapour retarder and two retarders with insulation between them can trap moisture. A contractor who can explain what they are doing on that wall, and why, is one worth hiring.
Who has to be qualified
Plumbing is not optional in this respect. Plumber is a compulsory trade in Ontario, trade code 306A, and to practise it legally a person must hold a Registered Training Agreement, a Provisional Certificate of Qualification or a Certificate of Qualification. The apprenticeship is 9,000 hours, of which 8,280 are on the job and 720 in school, and a Certificate of Qualification must be renewed to remain valid. Holders appear on the Skilled Trades Ontario public register, so ask for the name and check it.
Electrical work is equally clear. The Ontario Electrical Safety Code requires almost all electrical work to be reported to the Electrical Safety Authority through a notification of work filed before the work begins, and the ESA states that if you hire someone to do electrical work in your home, by law it must be a Licensed Electrical Contractor. A building permit is not the same as an electrical notification and you may need both.
Tiling, waterproofing and general contracting are not licensed trades in Ontario. There is no certificate to ask for, so ask about the system instead: which membrane, are you certified on it by the manufacturer, and does that give me a system warranty. And ask every contractor on the job for a WSIB clearance certificate and a certificate of liability insurance.
Sources
- City of Ottawa, Do I need a building permit
- Ontario Building Code, O. Reg. 163/24
- OBC 9.29.10.4, Moisture Resistant Backing
- OBC 9.29.10.5, Joints between Tiles and Bathtub
- OBC 9.32.3.4, Principal Exhaust
- OBC 9.32.3.5, Supplemental Exhaust
- Skilled Trades Ontario, Plumber, trade code 306A
- Electrical Safety Authority, Notifications and inspections