Adding a Basement Bathroom in Mississauga: Permits, Plans & Costs (2026)

Do you need a permit? Start with the work, not the room name

Important: This is a project-category comparison, not an approval for a particular address. The City determines your permit requirements after reviewing the proposed scope. Official permit triggers (opens in a new tab).

Can you hire someone for permit drawings and do some work yourself?

You do not have to start by signing a full design-build renovation contract. You can get a quote for design and permit coordination separately from construction, and decide which tasks you will perform yourself.

Ask each designer to specify exactly what the fee covers: site measurement, a scaled existing/proposed floor plan, plumbing layout, ventilation details, permit forms, ePlans submission, response to City comments and any required revisions. A cheap 'drawing package' may exclude most of those tasks.

Mississauga strongly recommends an architect, engineer or qualified designer for complete, accurate code-compliant drawings. Its finished-basement application includes a Schedule 1 Designer Information form. If you are considering preparing your own drawings, ask the City's Building Division which owner-designer exemptions, qualifications and declaration requirements apply to your building and proposed work. Do not assume you need a BCIN designer for every house alteration, or that doing your own drawings removes your responsibility to comply with the Code. See the City's drawing guidance (opens in a new tab) and Ontario's current Building Code resources (opens in a new tab).

For electrical work, a separate Electrical Safety Authority (ESA) notification may be required. ESA says eligible homeowners can perform electrical work in their own homes but must follow notification and inspection requirements. If you hire electrical help, use a Licensed Electrical Contractor and confirm who files the ESA notification. A municipal building permit is not a substitute for ESA approval. ESA's homeowner guidance (opens in a new tab).

Drawings and documents: what to prepare

If you are finishing a basement, Mississauga's official Finish basement checklist calls for the Applicable Law Form, Schedule 1 Designer Information and a Single Dwelling Unit Information Letter, plus a site plan and floor plans. The City can ask for more based on the proposal.

Your plan package should show:

• Existing versus proposed: room names and dimensions, walls to remain, walls to remove, new partitions, doors, windows and stairs.
• Plumbing: every existing and proposed sink, toilet, tub or shower, floor drain and ventilation provision.
• Mechanical and safety: supply/return grilles, required alarms, relevant framing and section references.
• Site information: address, property lines, legal lot information, buildings, easements and other items specified by the City's checklist.

For ePlans, upload separate, unsecured grayscale PDF files, with landscape orientation and filenames matching the drawing number and title, such as A02 BASEMENT FLOOR PLAN. Do not include your address, date or underscores in filenames. Finish-basement document checklist (opens in a new tab) and ePlans file standards (opens in a new tab).

Before requesting a drawing quote: Take photos of the basement, mark the location of the existing main drain, plumbing stacks, furnace, panel, ceiling bulkheads and any water damage. Mark what you cannot see as unknown. These photos help a professional scope the work; they do not replace measurements or an assessment.

What does the permit cost in 2026?

Mississauga's February 1, 2026 to January 31, 2027 schedule establishes:

• $244 minimum for a qualifying Part 9 residential building permit.
• A $50 non-refundable ePlans pre-screening payment, credited toward the total permit fee, not automatically added on top.
• A $5.64 per m² service index for finishing basements in detached houses, semi-detached houses, townhouses and duplexes.
• A $6.84 per m² Group C residential interior-alteration rate, with the applicable minimum, where that classification applies.

These are City permit-fee categories, not a confirmed quote for one bathroom. The City determines the applicable classification, measured area and any additional requirements during review. Plumbing-only alterations may be assessed differently from a whole-basement finish. If your planned work spans categories, ask the City how the fees will be calculated. The minimum still applies where relevant.

Not included in those permit numbers: private designer fees, plumber/electrician labour, fixtures, waterproofing, concrete cutting, unexpected repairs or potential separate ESA fees. Request those as separate quote lines rather than trusting a generic cost-per-square-foot figure.

Official 2026 Building Division Fee Schedule (PDF) (opens in a new tab) · City permit costs and timeframes (opens in a new tab).

How long should you allow?

Mississauga currently lists 7–10 business days for prescreening and a 10-business-day initial department review for complete residential applications. It publishes an average of seven weeks from application processing to issuance for residential alterations in detached and semi-detached houses. These are different measures and should not be added together as a promised completion date. Missing information and revisions add time; resubmission cycles may add two or more weeks.

Apply well before booking demolition or arranging trades. Submit through Mississauga ePlans (opens in a new tab) and wait until the permit and approved drawings have been issued before starting permit-required work.

Inspection order: what must stay visible?

Before starting, Mississauga advises booking an initial inspection to confirm the exact stages for your permit. Its published basement/plumbing instructions distinguish:

1. Inside drain inspection: underground drainage before it is covered with gravel or concrete.
2. Plumbing rough-in: supply, drain and vent pipes before drywall, and before the framing inspection.
3. Framing and any other required building/HVAC inspections: at the stage the inspector specifies.
4. Final plumbing/building inspections: completed, working fixtures and resolved deficiencies.

Do not cover the pipes or framing before the required inspections. Keep the approved drawings on site and make sure the permit status is closed when the work is complete. ESA electrical inspections are a separate process.

City of Mississauga: Book a building permit inspection (opens in a new tab).

A better request for quotes (copy this)

I'm adding a bathroom to an existing basement in Mississauga. The planned fixtures are [toilet, sink, shower]. The space is currently [unfinished / finished], and plumbing is [existing / new / unknown]. I may do some non-specialist finishing work myself. Please separate your quote into (1) drawings and permit application, (2) plumbing and any slab work, (3) ventilation, (4) electrical/ESA scope, (5) inspections and coordination, and (6) finishes. Specify exclusions, the person responsible for each permit or notification, and how unforeseen conditions are priced.

Five questions to ask before paying a deposit:

1. Are you pricing the specific bathroom or the entire basement permit scope?
2. Who measures and prepares the drawings, and what designer qualification or exemption applies?
3. Who submits through ePlans and answers City review comments?
4. Who books the underground-drain, rough-in and final inspections, and the separate ESA inspection if needed?
5. What happens if the slab, drainage slope, venting or existing framing makes the proposed layout impractical?

Your next step

Check your Mississauga property and project to see the municipal guidance BuildRules currently supports, then confirm the remaining questions with the City. Toronto has deeper mapped parcel-level data; Mississauga guidance is not a property-specific permit decision.

If you need a designer, plumber or contractor, browse professionals serving Mississauga. Business listing details and service areas help with comparison; they are not a guarantee of licensing, availability or project quality.

Sources checked: October 18, 2026. This guide explains published requirements. Only the City and relevant authorities can confirm the approval and inspection requirements for your specific work.