A plumbing renovation means replacing, relocating or adding the pipes, drains, vents, valves and fixtures in an existing home, often as part of a larger project like a bathroom, kitchen or basement. In Quebec, the work must be done by a contractor holding the right RBQ licence. It has to be sequenced with electrical, framing and drywall, and inspected before anything is covered. This guide walks through what the work includes, what to settle before it starts, and how to avoid the usual expensive surprises.
TL;DR
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A plumbing renovation covers supply lines, drains, venting, shut-off valves, fixtures and sometimes a backwater valve, not just swapping a faucet.
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In Quebec, plumbing work requires a contractor with the appropriate RBQ licence, including the plumbing contractor subclass. Ask for the licence number and check it.
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Plumbing and electrical rough-in compete for the same wall and ceiling space, so they must be planned together before walls close.
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Put scope, responsibilities, permits and costs in a written contract, as the federal Office of Consumer Affairs advises.
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One accountable team coordinating every trade removes most of the scheduling and blame problems.
Table of Contents
What a plumbing renovation actually involves
Most homeowners picture new taps and a vanity. The visible part is a small share of the job. A real plumbing renovation usually has three layers.
Supply. Hot and cold water lines running from the entry point to every fixture. Renovation is the moment to replace worn or mixed materials, add accessible shut-off valves and insulate pipes. CMHC’s sustainable-plumbing guide recommends accessible shut-offs, suitable materials and fittings, insulated hot and cold pipes, properly supported and sealed piping, and water-efficient fixtures.
Drain, waste and vent. Gravity-fed drains need the correct slope and each fixture needs venting. Moving a toilet, a shower or a kitchen sink means reworking this layer, and that is where costs climb. The same CMHC guide suggests checking existing drains for defects or sagging while the work is open.
Fixtures and appliances. Toilets, showers, tubs, vanities, kitchen sinks, dishwashers, laundry connections and water heaters. These are the choices you see, but their rough-in positions are fixed early, long before tile or cabinets arrive.
The scope depends on the room.
| Project | Typical plumbing work |
|---|---|
| Bathroom | Relocating drains or the shower valve, new rough-in for a vanity, toilet or tub, replacing supply lines, adding shut-offs |
| Kitchen | Sink and dishwasher relocation, new supply and drain runs for an island, gas or water lines for appliances, under-cabinet access |
| Basement | Rough-in for a new bathroom or laundry, drain connections below grade, a backwater valve, sump considerations |
| Whole home | Replacing old supply lines, updating drains and vents, new water heater, reorganizing risers |
If you are planning one of these, our guides on basement renovation planning in Montreal and common bathroom renovation mistakes cover the surrounding decisions.
Who is allowed to do the work in Quebec
Plumbing is a regulated trade here. The Régie du bâtiment du Québec states that carrying out plumbing work requires the appropriate contractor or owner-builder licence, including subclass 15.5, Contractor - plumbing. The RBQ also explains that the Corporation des maîtres mécaniciens en tuyauterie du Québec (CMMTQ) acts as its mandatary for plumbing and heating contractors, ensuring their qualifications and issuing the licence.
What that means for you:
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Ask any contractor for their licence number before you sign.
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Look the number up in the RBQ’s licence holders’ repertory.
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Confirm that the licence covers plumbing, not only general renovation.
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Make sure the contract names who will actually perform the plumbing, whether the contractor’s own team or a subcontractor.
A low quote from an unlicensed operator is not a saving. Unpermitted or non-compliant plumbing can surface when you sell, file an insurance claim or have a leak behind a finished wall.
Codes, permits and inspections
The National Plumbing Code of Canada 2020 sets technical provisions for new plumbing systems and applies to alterations, renewals and repairs of existing ones. Provinces and territories may adopt it with or without modifications, and can add their own rules, including requirements about who must be involved. In Quebec, that means the provincial construction rules and your municipality’s requirements govern your project, so confirm them locally.
Permit rules differ by city. As an example of how an inspection framework works, the City of Toronto’s guide to building permits says a permit is needed for renovations that install or alter mechanical or plumbing systems. It lists mandatory inspections: underground drains before covering, drainage and venting, water distribution before covering, and a final inspection once fixtures are in. Montreal-area municipalities have their own process, but the logic is the same everywhere: concealed work is checked while it is still visible.
The practical consequence is sequencing. You cannot close the walls on a Friday and call the inspector on Monday. Build inspection windows into the schedule. For the bathroom specifics, see our article on bathroom renovation permit rules.
The federal Office of Consumer Affairs treats renovations touching a home’s mechanical systems as retrofit work. It advises you to define the work, identify responsibilities, verify permits and inspections, and document scope and cost in the contract. Ask who pulls the permit and who books each inspection. The answer should be written down.
Check what you already have before the work starts
Plumbing renovation often begins with finding out what is behind the walls. CMHC’s homeowner inspection guidance says older plumbing should be assessed for pipe material and condition. It notes that lead pipes indicate an old system likely needing future upgrading, and recommends a qualified inspector assess sewage and drains.
Before demolition, ask for:
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Pipe material and condition at the entry, in accessible areas and at fixtures.
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Drain condition, especially in older Montreal-area houses where slopes may have shifted.
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Shut-off locations, and whether you have a main shut-off you can reach in seconds.
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Water heater age and whether its location suits the new layout.
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Backwater protection. The Government of Canada says homes with basements, ground-level floors, prior sewer backups or older sewer infrastructure may warrant a backwater-valve assessment. Installation should follow local requirements and be done by a licensed plumbing professional after inspection.
If you find lead or failing drains, the scope and budget change. It is far better to learn that in the quote stage than after the bathroom is half demolished.
Upgrades worth including while walls are open
Opening a wall is the expensive part. Adding a few items while it is open usually costs little compared with returning later.
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Accessible shut-off valves for each fixture or room, so a leak or later repair does not shut off the whole house.
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Insulated hot and cold lines in exterior walls, basements and unheated spaces. CMHC’s guidance lists pipe insulation and controlling hot-water distribution as part of sustainable plumbing.
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Water-efficient fixtures, which CMHC also recommends.
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Access panels where valves or cleanouts would otherwise be buried behind tile.
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A backwater valve if your home fits the risk profile described above.
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Rough-in for the future, such as a basement bathroom you plan to finish in two years.
None of these is exotic. They are the difference between a renovation that looks good for a year and one that is easy to maintain for decades.
Coordinating plumbing with the other trades
Plumbing sits in the middle of the renovation sequence. It follows demolition and framing, shares wall cavities with electrical and ventilation, and has to be finished and inspected before insulation, drywall and tile.
Two points from the research are worth planning around.
First, plumbing and electrical rough-in must be coordinated so they do not compete for space in walls and ceilings, with clear communication about access before walls are closed. A drain stack that needs a thick wall can collide with a panel feeder or recessed lighting. Walk the site with both trades before framing is finalized.
Second, a Canadian plumbing apprenticeship text explains that the general contractor bears ultimate responsibility for site coordination, holding regular meetings so the plumbing schedule fits with other trades without harming their work. The same text recommends a single point of contact, a project manager or general contractor, for relaying changes, because communication spread across several people leads to conflicting assumptions among sub-trades.
Here is a realistic sequence for a bathroom:
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Scope, drawings and fixture selection (fixtures decide rough-in positions).
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Permit application where required.
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Demolition and any structural framing changes.
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Plumbing and electrical rough-in, coordinated.
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Rough-in inspection while everything is visible.
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Insulation, drywall and waterproofing.
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Tile, flooring, cabinetry and painting.
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Fixture installation and final inspection.
The most common delay is step 1 incomplete: a toilet or vanity chosen late, with a different rough-in measurement from what is already in the wall.
What drives the cost
We do not publish fixed prices, because two plumbing renovations that look alike on paper can differ greatly. The factors that move a quote are consistent:
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Distance moved. Keeping fixtures where they are is cheaper than relocating drains, which need slope and venting.
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Access. Open framing in a basement is simpler than fishing pipes through finished plaster in a plex.
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Existing condition. Lead, corroded or mixed-material lines and sagging drains add scope.
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Floor type. Cutting a slab for a basement drain is a different job from working in a joist space.
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Material and fixture choices. Pipe type, valve quality and fixture grade all add up.
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Permits and inspections. Time and fees tied to approvals.
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Coordination. Repair work to walls, floors and finishes after plumbing is part of the real cost, so ask whether the quote includes it.
Be cautious with per-foot rules of thumb you find online. They are usually unsourced averages and vary across regions and years. A site visit and written quote are the only reliable answer. The Office of Consumer Affairs advice stands: get the scope and cost into the contract.
How to compare quotes
A clear quote lets you compare like with like. Check that each one:
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Names the RBQ licence number and the licensed party doing the plumbing.
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Lists what is included: demolition, rough-in, fixtures, permit handling, inspections, wall and floor repair.
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States what is excluded and how hidden problems, such as failing drains found after opening a wall, will be priced.
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Says who supplies fixtures and who is responsible if a delivery is late or wrong.
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Gives a schedule that includes inspection windows.
Beware of a plumber-only quote for a larger renovation. It may be cheaper on paper, but you then become the coordinator, chasing electricians, drywallers and tilers around someone else’s schedule.
Perspective: why we keep plumbing under one roof
We have seen the same pattern in renovation after renovation: the plumbing itself is rarely what goes wrong. What goes wrong is the gap between trades. A vanity is ordered with a different drain height. Electrical boxes land where a vent needs to go. Drywall is booked before the inspection is. Each tradesperson did their own job correctly and the project still stalls.
That is why we run plumbing, electrical, framing, drywall, painting, flooring and finishing through one licensed team with one point of contact. When the person answering your questions also controls the schedule, changes get relayed once, not four times. We think that is the most useful thing a renovation company can offer, because it removes the coordination work that homeowners and property managers should not have to do.
Our advice is simple: settle fixture choices early, decide on shut-offs and access panels before walls close, and treat inspection dates as part of the schedule, not an afterthought.
— Daricson Service
Plumbing renovation with Daricson
We handle plumbing as part of a full renovation or as a standalone specialty job in Greater Montreal. If you need the plumbing coordinated with electrical, framing, drywall and finishing, one team manages it from rough-in through the final walkthrough. See our plumbing services or the home renovation overview, then ask for a consultation and written quote. If electrical will be reworked at the same time, our electrical services team plans its rough-in alongside the plumbing.
We also have pages by area: Montreal, Laval, the South Shore, the West Island and Mirabel.
FAQ
Do I need a licensed plumber for a renovation in Quebec?
Yes. The RBQ says plumbing work in Quebec requires the appropriate contractor or owner-builder licence, including the plumbing contractor subclass. Ask for the licence number and check it in the RBQ’s repertory before signing.
Do plumbing renovations need a permit and inspection?
Often, yes, but the rules depend on your municipality and the scope of the work. Cities such as Toronto require permits for altering plumbing systems and inspect concealed drains, venting and water lines before they are covered. Ask your contractor which approvals apply to your address, and who is responsible for booking each inspection.
Should I add a backwater valve during a renovation?
It is worth an assessment if you have a basement, ground-level floors, a past sewer backup or older sewer infrastructure, according to the Government of Canada. Installation should follow local requirements and be done by a licensed plumbing professional after inspection. Doing it while floors or drains are already open is usually more convenient.
How do plumbing and electrical work fit together?
Both need space inside walls and ceilings, so they are roughed in at the same stage and should be planned together. Walk the site with both trades before framing is final and agree on access before drywall goes up. A single coordinating team makes this much easier.
Can I keep fixtures where they are to save money?
Usually yes, since moving drains means new slopes, venting and wall or floor work. Keeping a toilet, shower or sink in place limits the plumbing scope. Still, use the open walls to replace worn supply lines and add shut-off valves.