The short version
A basement bathroom is a plumbing job before it is a finishing job. The first question is whether the new drains can reach the house’s main drain by gravity. Moisture and ceiling height come next. Etobicoke is part of the City of Toronto, so Toronto Building issues the permit and inspects the work.
The plumbing
Gravity drain or ejector pump
The main drain carries waste to the city sewer. In many houses it runs under the basement floor, and new fixtures that can slope down to it drain by gravity, like the bathrooms upstairs.
In some houses the main drain leaves through the foundation wall above the floor, or sits too shallow. Then the waste goes to a sealed sewage sump, and a pump called an ejector lifts it into the drain. Ontario’s Building Code generally allows a pumped sump only for piping too low to drain by gravity. It also generally calls for the sump to be water-tight, air-tight and vented, with a backwater valve and a shut-off valve on the discharge pipe. An ejector stops when the power does, and it changes both the layout and the budget.
Breaking the slab
New drains run under the concrete. The floor is cut, a trench is dug to the main drain, and the new pipe is tied in at a slope. The drains are tested and inspected before the trench is filled and the concrete poured back. The closer the bathroom sits to the existing drain, the shorter the trench.
Venting
Each fixture trap needs a vent to drain properly and keep sewer gas out. The code generally requires a vent pipe, which in a basement often means running one up the wall to the existing stack. In limited cases, such as renovations, it also permits an air admittance valve, a one-way valve that lets air in, as long as it stays accessible and the system keeps at least one vent to the outdoors. Your plumber and designer confirm which applies.
Upflush and macerating toilets
A macerating toilet grinds waste and pumps it through a small pipe, so it can sit away from the main drain, often with less concrete cutting. Ontario’s Building Code generally allows one only where no connection to a gravity drain is available. The code also expects it to meet the CSA/ASME standard for these systems and to be installed to the manufacturer’s instructions, and it still counts as new plumbing, so expect a permit. It needs power and makes noise when it runs. Manufacturers also limit what can go down it.
Backwater valves
A backwater valve is a flap in the drain that closes when the city sewer backs up. Where a drain may be subject to backflow, Ontario’s Building Code generally calls for backwater valve protection on fixtures below the level of the street. Your plumber confirms what your house needs, and the City’s inspector checks it.
The City of Toronto lists a backwater valve as work that needs a building permit, with an inspection before it is covered. While the valve is closed, do not use any plumbing fixtures in the house: the water cannot drain and will back up inside. An alarm can tell you when it has closed.
The City’s Basement Flooding Protection Subsidy Program was running when we checked in November 2026, and it can pay part of the cost of a backwater valve. The valve has to be permitted and inspected, and the installer needs the right type of City business licence. Check toronto.ca for the current amounts and terms.
Moisture, ventilation and ceiling height
Basements run damp. Check for leaks and past water before anything is framed, because finishing over a damp wall is how basement mould starts. The shower needs a proper waterproofing membrane and the walls need moisture-resistant board.
The Building Code generally calls for an exhaust fan, switched in the room, in any bathroom the house’s main ventilation fan does not draw from, and does not let exhaust ducts discharge into enclosed spaces. In practice that means a fan ducted outside, not into the ceiling.
The code also sets minimum ceiling heights for basement space, with a lower allowance under beams and ducts, and a separate minimum for second suites. Ducts, beams and new pipe runs eat into that height, so your designer checks it before the layout is final.
Permits and inspections
Etobicoke became part of the City of Toronto at amalgamation in 1998, so City of Toronto Building rules apply. The City lists installing or modifying plumbing, including in a basement finish, as work that needs a building permit. Repairing or replacing a fixture does not. A new basement bathroom is new plumbing.
For a house, the City’s interior alterations guide asks for floor plans showing all plumbing fixtures, sections showing floor-to-ceiling heights, and a Plumbing Data Sheet. The City’s inspection schedule for houses typically includes:
- Under-floor drains, tested before they are covered.
- Rough-in of the water supply, drains, waste and vents, tested before the walls close.
- Final plumbing, once the fixtures are in.
Framing and insulation inspections may also apply. Anything covered before it passes has to be opened up again. The City says inspections happen within two business days of a request.
The fan, lights and outlets are electrical work, which is generally filed separately with the Electrical Safety Authority (ESA). A final inspection closes the building permit; the City notes that open permits can get in the way of a future sale.
Decisions to make before the design is final
- Shower or tub. Decide early. The drain is set in concrete, so a change of mind later means cutting the floor again.
- Location. Close to the existing drain and stack means a shorter trench. Farther away may suit the layout better, at the cost of more concrete to break.
- Gravity or pump. If gravity drainage is possible, the code generally expects it. If not, the choice is an ejector or, where allowed, a macerating unit.
- Second suite. If the basement might become a legal second suite, say so before the drawings. A suite needs its own permit and has extra code requirements. See legal basement apartments.
Timeline
| Stage | What happens | Sign-off |
|---|---|---|
| Design | Drain depth, moisture and height checked; drawings | Your approval |
| Permit | Drawings and Plumbing Data Sheet filed | Permit issued |
| Slab and drains | Floor cut, new drains tied in | Drain inspection before the trench is filled |
| Framing and rough-in | Walls, vents, water lines, fan duct, wiring | Plumbing rough-in inspection; ESA |
| Finishes | Board, waterproofing, tile, fixtures | Final inspection |
As part of a full basement finish, a bathroom typically adds about two weeks to the six to ten weeks on site, and permit review usually takes two to four weeks before work starts. A stand-alone basement bathroom gets its own written schedule with the estimate, because slab work varies from house to house. If you are finishing the whole basement, rough in the drains at the start; adding them later costs far more. If you are renovating upstairs too, read about main floor and basement renovations together.
What it costs
The basement renovation cost guide puts a basement bathroom at $15,000 to $25,000, and breaking concrete for new drains is most of it. For a whole basement, the guide’s tiers run $40,000 to $60,000 for a basic finish with no bathroom, $60,000 to $90,000 for a mid-range finish with a three-piece bathroom, and $90,000 to $150,000+ for a legal basement apartment. Add 13% HST and a 10 to 15% contingency.
How YAREX builds basement bathrooms
We check the drain depth, the layout and any history of water at the free estimate. We produce the drawings, file the permit and book the inspections. The bathroom is built the way we build any bathroom renovation: waterproofing, plumbing, electrical, tile and fixtures under one fixed-price contract, with allowances for what may be behind the walls stated up front. YAREX is licensed and insured, and because we also do water damage restoration, we build basements to stay dry.
Read more about basement finishing and bathroom renovation, or call (343) 947-2298 for a free estimate in Etobicoke, Toronto and the GTA.
Published November 3, 2026.
The service behind this guide
YAREX Renovation & Restoration, a licensed and insured contractor based in Etobicoke, finishes and renovates basements in Etobicoke and across Toronto and the GTA.
Basement Finishing in Toronto & Etobicoke
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