What counts as an ADU in Hamilton?
The City defines it as a separate self-contained unit located on the property of a principal (main) dwelling. The unit may be created within, added to, or detached from the principal dwelling.
(City of Hamilton, Additional Dwelling Units, read November 5, 2026) The Ontario Building Code calls the same thing a secondary suite, and older zoning documents call it a secondary dwelling unit. Those are three ways to build one:
| Where it goes | The City's example | |
|---|---|---|
| Inside the house | A basement in an existing house converted into a separate unit | Basement apartments |
| Added onto the house | A new addition built for a separate unit | Additions |
| Its own building | A new detached building in the yard, or a detached garage converted into a unit | Garden suites |
How many units can one lot have?
On an ordinary house lot, usually three: the house and two ADUs. The City's ADU team reviews permits for existing single family dwellings including up to two internal units & one detached unit
, and its page notes a maximum of four units in some zones. A house that ends up with three or more units is treated as multi-residential and reviewed by the City's Building Engineering staff instead (City of Hamilton, read November 5, 2026). Whether your own lot qualifies is in its zoning, which the City's interactive zoning map shows by address.
What does the zoning by-law say about a detached ADU?
On most urban lots, Hamilton's city-wide Zoning By-law 05-200 sets the size and the distances. These are the main rules for an additional dwelling unit, detached, as written into section 4.33.2 by By-law 22-132 in 2022 (City of Hamilton By-law 22-132) and changed by By-law 25-033 in March 2025 to meet the province's rules (City of Hamilton By-law 25-033), both read November 5, 2026:
| Rule | What the by-law says |
|---|---|
| Where on the lot | Rear yard or interior side yard only, and not closer to a flanking street than the house |
| From the side and rear lot lines | At least 1.2 metres, with a landscaped strip in the side yard |
| From the house, in the rear yard | At least 4.0 metres from the back wall of the house (it was 7.5 metres until By-law 25-033) |
| From the house, in a side yard | At least 4.0 metres from the side wall, and at least 5.0 metres back from the front of the house |
| Height | 6.0 metres at most, with no balcony or rooftop patio above the first floor |
| Floor area | The smaller of 75 square metres or the floor area of the house |
| Lot coverage | All buildings and structures on the lot together cover 45 per cent of it at most |
| The way in | A clear path from the street to its door, at least 1.0 metre wide with 2.1 metres of headroom |
| Yard | At least 12.0 square metres of landscaped area kept in the rear yard |
Two things change this table for some lots. Parts of the city still sit under a former town's zoning by-law, and each of those by-laws has its own ADU rules; the areas page lists them. And on rural land, By-law 24-039 allows a detached ADU only on a lot of at least 1.5 hectares (City of Hamilton By-law 24-039, read November 5, 2026). The City's zoning desk confirms the rules for one address.
What if my design does not fit the by-law?
You can ask for a minor variance. The City: If the proposed ADU design does not conform to the Zoning By-law then an application can be made for a minor variance. If approved, a minor variance can grant permission for alternative provisions relating to the land, building or its use.
(City of Hamilton, read November 5, 2026) The Committee of Adjustment decides it at a public hearing, before the building permit.
What else does the City ask for?
A building permit for both kinds: the City's list includes adding additional dwelling units (ADU Internal), including municipal addressing and street naming
and additional dwelling units detached (ADU Detached), including municipal addressing and street naming
(City of Hamilton, Building Permit Application Requirements, read November 5, 2026). A new unit also needs its own municipal address, with its own fee. Some detached ADUs need a professional grading design, and a detached unit needs an information notice posted at the site while it is built (City of Hamilton, Residential Infill, read November 5, 2026). Near a creek, on a heritage property or by the escarpment, other approvals come first. Who applies for a building permit in Hamilton covers the application and the inspections.
Does a detached ADU need a builder with a licence?
Generally yes, under Ontario's new home rules, separate from the City permit. The Home Construction Regulatory Authority says Coach, laneway, and 'tiny' homes generally require licensing and warranty coverage
, while renovations or upgrades to an existing home do not make the home "new"
(Home Construction Regulatory Authority, read November 5, 2026). So a unit inside the house is a renovation, and a new building in the yard is usually a new home. Who may build a new home explains the rule and how to check a builder, and basement unit or garden suite compares the two side by side. Whether your lot qualifies at all is in can my house have an ADU?, and the City's closed grant in money for an ADU.
How does JDT run an ADU build?
The same way as every JDT job. The ADU is drawn on a picture of your own house and lot before there is a price, so you see where it sits and how big it is. The whole scope and price go into one written proposal, the work is paid in stages as each stage is finished, and you follow it on your own project page. The agreements page has how the payments, changes and permit work. Thinking of a bigger change to the house itself? Renovations covers the work inside.
How do I start?
Call (905) 818-0106, or send a request with photos of the house, the yard or the space you have in mind, and the address so the zoning can be checked.