Adding a Second Unit to a Brockville Home: What the Rules Allow Now

This matters if you are buying with a plan: room for a parent, a basement rental to help with the mortgage, or a garden suite for an adult child. The time to test that plan is before you firm up the deal, not after closing.

If the house already has a unit and you want to know whether it was done legally, that is a different question, and it is covered in buying a house with a basement apartment in Ontario. This article is about adding one.

What Ontario changed, and why Brockville's own by-law may look out of date

In 2022 the province amended the Planning Act. Section 35.1 now says a municipal zoning by-law cannot prohibit additional residential units on what the Act calls a parcel of urban residential land: a lot inside a settlement area, zoned for residential use, and served by municipal sewage and water works. On that kind of lot, the City cannot prohibit:

• two units in a detached house, semi-detached house or rowhouse, plus one unit in an ancillary building such as a garden suite or coach house, or
• three units inside the house, with no unit in an ancillary building.

The same section says a by-law cannot require more than one parking space for each of those additional units, and cannot set a minimum floor area for them. Any by-law provision that contravenes those restrictions is of no effect.

Here is the part that trips people up. The general provisions section of Brockville's Comprehensive Zoning By-law 050-2014 posted on the City's website still says only one second suite or garden suite is permitted per lot, and that a garden suite needs a temporary use by-law. The City's own page on second units, posted in November 2022, explains that the provincial change now allows up to three units on lots with full municipal services. Where the two disagree on the number of units, the provincial rule in section 35.1 is the one that controls. The practical takeaway is simple: do not rule a property in or out based on an older by-law excerpt. Ask City planning staff what applies to that address today.

Does the house qualify in the first place?

Before you think about layouts, three facts about the property decide whether the provincial rules apply at all.

• Municipal water and sewer. The protection in section 35.1 applies to lots served by municipal sewage and water works. Most homes inside the City of Brockville are. Many rural homes in the surrounding townships, including parts of Elizabethtown-Kitley and Augusta, are on a well and septic system, and those lots fall outside this rule. There, the township's own zoning and the septic system's capacity decide what is possible.
• House type. The rule covers detached houses, semi-detached houses and rowhouses. A condominium unit or an apartment building is a different situation.
• Units already on the lot. The count is per lot. A house that already has a legal second unit has one less to add.

If you are moving from Ottawa with family in mind, the same check applies to every property on your list. Our guide to moving from Ottawa to Brockville covers the wider move; this is the piece that decides whether a specific house can hold two households.

What the City of Brockville still controls

The province removed the City's ability to say no to the units themselves. It did not remove the ordinary zoning and building rules that apply to the building and the lot. Here is how the pieces line up.

The lot coverage and separation standards come from Ontario Regulation 462/24, which the province filed in November 2024 to set minimum standards for lots and buildings with additional units. It also says the minimum lot area for a lot with additional units is the same as it would be without them.

Parking is usually where the plan gets tested

On many older Brockville lots, the hard question is not whether a unit is allowed but where the car goes. The City's rule is one legal parking space for each unit, and a legal space is 2.75 metres wide and 5.5 metres long. If the existing driveway barely fits one car beside the house, the measuring tape will tell you more than the listing will.

Basements have one extra Brockville check

The zoning by-law permits a dwelling unit in a basement only where the finished floor is above the level of the sanitary or storm sewer. It also notes that units in the Cataraqui Region Conservation Authority's screening area may need a permit from the conservation authority. Neither of those is something you can see at a showing. Ask City staff how they apply to the address, and if the property is near the river or a creek, read our piece on what a floodplain designation actually changes.

Permits and safety come next

Zoning tells you whether a unit can exist on the lot. The building permit is where it actually gets approved. Ontario's guide to adding a second unit says you will need a building permit, and that the Electrical Safety Authority inspects the electrical work in the new unit. The City notes that its Building Department reviews fire separation and other safety requirements under the Ontario Building Code.

In practice that means drawings, fire separation between units, smoke and carbon monoxide alarms, a safe way out of the unit, and electrical work done under a permit. A designer or contractor who does this work regularly can tell you what a specific house needs. The point for a buyer is that the cost of meeting those requirements belongs in your numbers before you decide what the house is worth to you.

Is there any funding for a new unit?

The United Counties of Leeds and Grenville run secondary suite programs that provide funding as a forgivable loan to build a new secondary suite, not to renovate an existing one. The unit has to be rented at or below an affordable rent set by the Counties, to a renter whose income and assets are below set limits, and the renter can be a relative such as an elderly parent or adult child.

When this article was written, the Counties' program page said the homeowner funding had been exhausted for 2024 and that funding for the landlord program was still available. That status changes, so check with the Counties directly before you count on it.

A quick checklist before you write the offer

• Confirm the house is a detached, semi-detached or row house on City water and sewer.
• Ask City planning staff what zoning applies to the address and how many units it can hold today.
• Measure where each required parking space would go.
• If the unit would be in the basement, ask how the sewer-level rule applies, and whether the lot is in the conservation authority's screening area.
• If it would be a garden suite, check the 4.0 metre height limit, the setbacks, and the 4 metre separation from the house unless the by-law allows less.
• Get a rough sense of the permit and construction work from someone who builds these units.
• Talk to your lawyer about conditions and timing if the plan is the reason you are buying.

Common questions

Can I add a unit to a house outside the City, in Elizabethtown-Kitley or Augusta?

Possibly, but the provincial protection in section 35.1 is tied to lots on municipal water and sewer. A rural lot on a well and septic system is governed by the township's own zoning and by what the septic system can handle. Start with the township, not with the Brockville rules.

Do I have to live in the house to add a second unit?

Nothing in section 35.1 makes the protection depend on who lives in the house, but ask the City whether anything else in its by-law applies to the address. The Leeds and Grenville funding programs are different: the homeowner track and the landlord track have their own eligibility rules, so read the program documents before you apply.

For a wider look at living and buying in the city, see our Brockville real estate guide.