GTA ADU Permit Fees Compared: What 12 Municipalities Charge

Key takeaways

• Across the GTA, ADU permit and development fee bands run from about $5,500 at the low end to about $16,500 at the high end, a spread of roughly $11,000 on the same building.
• Fees are set locally, re-set annually, and layered: city charges plus regional charges plus, on unserviced lots, septic permit charges.
• Mississauga refunds its additional residential unit permit fee, about $1,050 for a 600 sq ft suite at the 2025 rate, in full once construction passes final inspection.
• The lowest fee band does not produce the lowest project cost. Site access and servicing distance move a budget far more than permit fees do.

Permit fees are the part of an ADU budget that homeowners research first and understand least. The number is not one fee, it is a stack, and the stack is assembled differently in every municipality. A homeowner comparing a quote in Oshawa with a quote in Caledon is often comparing two different fee structures without realising it. This post lays out the current bands so the comparison is at least being made on the same terms.

ADU permit fees across the GTA, municipality by municipality

The figures below are the bands we budget against, drawn from the per municipality fee data we maintain in our service area records. They cover permit, development and plan review charges taken together, which is the number that actually leaves your account before construction starts. They do not include design, survey, arborist or engineering costs, which we quote separately.

Two patterns come out of that table immediately. Peel and Durham municipalities sit at the lower end, York Region municipalities at the upper end, and Halton in between. And the municipalities with septic charges in the mix, King and Caledon among them, carry the highest bands because an unserviced lot adds a separate approval with its own fee.

Why the bands are so wide within one municipality

A band of $8,000 to $14,000 in one city is not vagueness on our part. Several of the components scale with the project rather than being flat, so the same municipality produces a different total for a different unit. The variables that move you within a band are consistent across the GTA:

• Unit floor area, since several charges are calculated per square metre.
• Whether the lot is on full municipal services or requires a septic permit.
• Whether a minor variance is needed, which adds a Committee of Adjustment application.
• Whether the lot sits inside a conservation authority regulated area, which adds a review.
• Resubmissions, which happen when a permit package answers the building department's comments poorly the first time.

That last item is the one within a builder's control rather than yours. A permit package that anticipates the municipal comments clears in one pass. One that does not can add weeks and a resubmission fee. It is a large part of why we run permits and design as a single scope rather than handing drawings to someone else to defend.

The refund most Mississauga owners miss

Mississauga runs an additional residential unit permit fee of about $1,050 for a roughly 600 sq ft suite at the 2025 rate. The part worth knowing is that the city refunds that fee in full once construction passes final inspection. It is effectively a deposit against completion rather than a cost, provided the project is actually finished and inspected.

Brampton is a different case again. The city's Residential Second Unit registration program means the most frequent first step there is not a new build but legalising an existing basement apartment, brought up to Ontario Building Code fire separation standard. That is a materially different fee path from a detached garden suite, and it is why Brampton sits at the bottom of the table above while still being a substantial project.

How to read fees against total project cost

Here is the part that reframes the whole table. A detached unit of 500 to 600 sq ft in the Greater Toronto and Hamilton Area runs roughly $200,000 to $350,000 to build, per the figure Resimate CEO Sarah Cipkar gave CBC News in July 2025. Against that, the full spread between the lowest and highest GTA fee band is about $11,000. Fees are real money and they belong in the budget, but they are not where projects go over.

Where projects go over is site work. Rank the variables by how much they actually move a total:

1. Site access, which decides excavation method, material handling and equipment entirely.
2. Servicing distance, since trenching water, sanitary and hydro across an established yard is real money.
3. Soil and grading, which drive the foundation design.
4. Finish level, which is the part you control and the part quoted last.
5. Permit and development fees, which are known in advance and vary by roughly $11,000 region wide.

We do not publish a single ADU construction price, because the same unit on two GTA lots is not the same job. What we do is a paid feasibility, then a fixed scope price, with permit fees quoted as a separate line so the permit stage is never where your budget moves unexpectedly.

Frequently asked questions

Are these fees current?

They are the bands we budget against as of the 2025 rate schedules, and municipalities re-set fees annually. We verify the current schedule for your specific municipality during feasibility rather than quoting from a published table, because a fee that changed in January should not surprise anyone in March. Treat the table above as a planning range, not a quote.

Do I pay development charges on an ADU?

The charges that apply depend on your municipality, the unit type and current provincial exemptions for additional residential units, which have moved with the recent legislation. This is exactly the kind of item we confirm in writing with the municipality during feasibility. We would rather establish it before contract than discover it at permit stage.

Can I reduce the fees?

Not directly, since they are set by by-law. What you can influence is the number of applications your project needs. Avoiding a minor variance where the design can reasonably comply, and submitting a permit package that clears in one pass rather than three, is usually worth more than any fee difference between neighbouring municipalities.

Should I choose a municipality based on fees?

No, and in practice nobody can, since you are building on the lot you own. The table is useful for budgeting accurately, not for choosing where to build. If you are weighing two properties, servicing distance and rear yard depth will affect your total far more than the fee band will.