Legal Basement Apartment in Milton (2027): Rules, Permits and Costs

By Jatin Dua · Broker of Record, RE/MAX Quantum Realty · Updated 2 November 2026 · 9 min read — Milton’s ARU eligibility, permit fees, $340 registration and yearly renewal for a basement suite in 2027, with a worked example and market numbers.

This guide is for Milton homeowners planning a basement apartment, owners who already have one that was never registered, and buyers looking at a house with a second unit. You will get the Town’s eligibility rules, the building permit steps and fees, how the ARU registration pilot works, and current price and rent numbers for Milton.

Is a basement apartment legal in Milton in 2027?

Yes. Milton calls these units additional residential units, or ARUs. Council approved Official Plan and zoning changes in June 2024 to allow them in the urban area, and in January 2026 the Town updated its rules again to allow ARUs in rural areas where provincial policy permits.

A basement suite in Milton is legal when it passes four tests:

1. your property is eligible and the unit meets the Town’s zoning standards;
2. it was built under a building permit and passed its inspections;
3. it is registered with the Town and has a compliance certificate;
4. that registration is renewed every year.

The fourth point is what makes Milton different from most of the GTA. Registration here is not a one-time event.

Why Milton insists on registration

The Town says every ARU must be registered, new or old, with no grandfathering. It applies whether the unit is rented, used by family, or sitting empty. Unregistered units can face enforcement, including Fire Code charges and fines.

Which Milton properties can have an additional residential unit?

The Town’s Build an ARU page sets out who qualifies.

Urban Milton

• The lot must have municipal water and sewer.
• The house must be detached, semi-detached, semi-link or a townhouse. Stacked and back-to-back townhouses are excluded.
• Up to four units in total are allowed, counting the main home.
• Only one ARU can be in a detached building such as a coach house.
• Urban lots without full municipal services in low-density zones may get up to two ARUs.
• If your home is in a condominium corporation, check the corporation’s own rules too.

Rural Milton

• On RV or C4 zoned lots outside the Niagara Escarpment Plan Area, one ARU may be allowed.
• Inside the Escarpment plan area, one ARU only in a detached house, and no detached ARUs.
• In the Greenbelt Protected Countryside, none inside the Natural Heritage System, and one elsewhere.
• On A1 lots outside the Greenbelt, up to two ARUs, with only one in a detached building.

Not every eligible lot can physically fit a unit, so treat eligibility as step one, not a yes.

What zoning rules apply to a Milton basement apartment?

The Town’s urban rules are in Zoning By-law 016-2014, as amended in 2024. The Town says the zoning standards affect where the ARU can go, its size, parking and the placement of detached structures. A 2024 Town notice on a housekeeping amendment explains that section 4.10 of the by-law requires an ARU entrance to have unobstructed pedestrian access from the street, so plan a clear walkway.

Two provincial limits help you here:

• Ontario’s Planning Act does not let a municipality require more than one parking space for each additional unit.
• Development charges are not collected for a second unit built inside an existing house, according to Ontario’s guide to adding a second unit.

If your plan does not meet a zoning standard, the Town says you may be able to apply for a minor variance. That adds time and cost, so check zoning before you pay for drawings.

One more Milton rule catches people: the Town says cooking facilities are not permitted in a finished basement unless the space is approved as a secondary dwelling unit. A basement kitchen without that approval is a problem on resale.

What Building Code rules does a basement unit have to meet?

Most Milton basements are in houses more than five years old, so Ontario’s guide for existing houses applies. A newer house must meet new-construction rules. The main checks:

• Ceiling height: at least 1.95 metres over the required floor area, including the route to the exit.
• Room sizes: for example 9.8 m² for a main bedroom without a built-in closet and 4.2 m² for a kitchen.
• Windows: glass equal to 5% of floor area in living and dining rooms, and 2.5% in bedrooms.
• Escape window: 0.38 m² of clear opening, no side under 460 mm, sill no higher than 900 mm.
• Fire separation: 30 minutes between units, or 15 minutes if all smoke alarms are interconnected.
• Heating: one furnace may serve both units with a duct smoke detector that shuts it down.
• Plumbing: each unit needs a kitchen sink, toilet, basin and tub or shower, laundry access and its own water shut-off.

How do you get a building permit for a basement apartment in Milton?

A permit is required before construction. The Town’s ARU page lists what to submit:

• a completed Permit to Construct or Demolish application;
• a Schedule 1 Designer Information Form, if an architect or engineer did not prepare the plans;
• a site plan and existing and proposed floor plans;
• construction details, including wall, ceiling and fire separation information;
• drawings showing entrances and windows.

Applications go through the Town’s online portal. Once the package is accepted, the Town invoices the permit fee, and the full review begins after you pay. Electrical work also needs a separate permit from the Electrical Safety Authority, as Ontario’s guide notes.

Which inspections to expect

For basement work, the Town lists framing, insulation and air barrier, below-grade, above-grade and final plumbing, heating rough-in and final heat, and a final building inspection. Book each one as the work reaches that stage.

How does Milton’s ARU registration work?

Milton’s registration program started April 1, 2025, and runs as a three-year pilot. The Town says the rules may change when the pilot is reviewed. Here is how it works today:

1. Apply: online, or at the Community Services desk at Town Hall.
2. Pay: $340 per ARU.
3. Inspection: a municipal law enforcement officer and a fire prevention officer visit, usually for about 30 minutes. The owner must be there, and the time is set to suit the tenant too.
4. Certificate: if it passes, you get a compliance certificate by email.
5. Renew yearly: the certificate lasts one year. The Town emails a renewal form about 30 days before expiry. During the pilot, renewal is free.

What the inspectors check

• smoke alarms work and are interconnected through the building;
• a carbon monoxide alarm works on each level;
• required fire separations are intact;
• exterior access routes are clear;
• the sump pump and furnace room are easy to reach;
• the property meets the Property Standards By-law.

The ARU does not get its own street number. It uses a unit number on the same address, such as 123-1, and your house number must be clearly visible from the street.

How much does a legal basement apartment cost in Milton?

Construction cost depends on the basement. Town fees are published, so here is a worked example for a 75 m² suite with a new side door, one enlarged window and new plumbing.

Source: Town of Milton building permit fee table and ARU registration page, read November 2026. Design, electrical permit and construction are extra.

Build without a permit and the costs climb. The Town lists an order to comply at $338.86 and a stop work order at $676.57, and a revision to plans after review costs $436.51. Ask MPAC how a second unit may affect your property assessment, as the Town itself suggests.

Is a basement apartment worth it in Milton?

Milton prices fell in 2026, which matters if you are paying extra for a house with a suite.

Source: TRREB MLS data via REALM, January–October 2026 vs the same period of 2025, Town of Milton. Median sold prices, not forecasts.

For rent, TRREB’s Q2 2026 rental report shows Milton condo apartments leasing at an average of $2,071 for a one-bedroom and $2,576 for a two-bedroom. Basement rents are not published by TRREB, so use those figures only as an upper reference. A basement unit created after November 15, 2018 in unfinished space, or while the owner lived upstairs, is generally exempt from Ontario’s rent increase guideline, though 90 days’ notice and the 12-month rule still apply.

For the full Halton picture, see my Halton market outlook for 2027, and if you are budgeting carrying costs, my Milton property tax guide.

What to do next

Follow these steps in order.

1. Confirm your property type and zone qualify, using the Town’s eligibility list above.
2. Hire a qualified designer, prepare drawings and apply for a building permit through the Town’s portal.
3. Book every inspection, then register the ARU and pay the $340 fee.
4. Diarise the yearly renewal so the certificate never lapses.
5. Read my notes on buying a house with a basement apartment, and check your home’s value with what Milton houses are worth.

Frequently asked questions

Sources

• Town of Milton: Build an ARU
• Town of Milton: Register an Existing ARU
• Town of Milton: Renew Your ARU Registration
• Town of Milton: Building Permits (rates and fees)
• Town of Milton: Finished Basements
• Town of Milton: Town Introduces Additional Residential Unit Registration Program
• Government of Ontario: Add a second unit in your house
• TRREB Rental Market Report, Q2 2026

Related reading

• How Much Does a Fourplex Cost to Build or Buy in Toronto?
• Converting a House to a Triplex in Toronto: Cost, Permits and Payback
• Multiplex Benefits for Toronto Homeowners: Rent, Value and Family Living
• Legal Basement Apartment in Brampton (2027): Rules, Permits and Costs