Which basement work needs a permit?
Most of it. These are from the City's own list of projects that need a building permit (City of Hamilton, Building Permit, read November 5, 2026):
| Work | Permit? |
|---|---|
| Finishing or partially finishing a basement | Yes |
| Installing or replacing drywall and insulation | Yes |
| New rooms, or moving rooms | Yes |
| Adding or removing walls, load bearing or not | Yes |
| New or moved plumbing, a backwater valve, a sump pump, an interior weeping tile system | Yes |
| A walkout basement | Yes |
| Underpinning to make a full basement | Yes |
| Waterproofing foundation walls | Yes |
| Flooring, cabinetry, painting, replacing fixtures in the same place | No |
What does the permit cost?
$4.06 a square metre to finish a basement, and $6.58 for a new basement or cold cellar, with a $291 minimum (City of Hamilton, Building Permit Fees, read November 5, 2026). Finishing 80 m² comes to $325. A basement that becomes its own apartment is charged differently, a flat $515: the permit fee calculator has both.
When does a basement become an ADU?
When it is a separate, self-contained home with its own kitchen and bathroom. That is an additional dwelling unit, with fire separations, exits, smoke alarms and a furnace shut-off the City lists (City of Hamilton, Additional Dwelling Units, read November 5, 2026). Making a basement apartment legal covers it, and the backwater valve grant covers protecting the basement from sewer backup.
What if the basement was finished without a permit?
The City can order a permit after the fact, and opening walls for the inspector costs more than building it right; building without a permit lists what the City can do. Taking out a wall down there has its own page: removing a wall.
How does JDT run a basement?
Framing, insulation, drywall, a bathroom and the finishes, drawn first and priced in one written proposal, with the work paid in stages; renovations has the rest. Under JDT Construction Inc.'s agreement the homeowner applies for the permit and pays the City's fees; who applies for a building permit explains how that works.