Basement Apartment Contracts: Protecting Your $100K+ Investment
Converting a basement into a legal secondary suite is one of the most complex residential renovations in Ontario. It requires coordination across multiple trades, multiple permits, multiple inspections, and compliance with the Ontario Building Code's fire separation and life safety requirements. At $100,000 to $180,000 for a typical GTA project, it is also one of the most expensive.
Your contract needs to reflect this complexity.
Why Basement Apartments Need the Most Detailed Contracts
Unlike a single-trade renovation, a basement apartment involves:
A contract that says "finish the basement for $120,000" is not sufficient. You need a contract that specifies exactly what happens at each stage.
The 6-Milestone Payment Structure
Basement apartments should use a 6-milestone schedule that aligns with inspection stages:
| Milestone | % | Amount (on $120K) | Key Deliverables |
|---|---|---|---|
| Demolition & Prep | 10% | $10,800 | Existing finishes removed, site prepped, underpinning (if needed) |
| Structural & Framing | 20% | $21,600 | All framing complete, fire separation installed, structural mods done |
| Rough-In (MEP) | 20% | $21,600 | Plumbing, electrical, HVAC rough-in, inspections passed |
| Inspections & Insulation | 15% | $16,200 | All rough-in inspections passed, insulation installed, vapour barrier |
| Finishes & Fixtures | 25% | $27,000 | Drywall, flooring, kitchen, bathroom, paint, fixtures |
| Final Inspection & Cleanup | 10% | $10,800 | Final municipal inspection, occupancy certificate, site cleanup |
| **10% Holdback** | **$12,000** | Released 60 days after substantial completion |
The 10% holdback applies to the full $120,000, totalling $12,000 held for 60 days.
Permit Stages and Responsibilities
Your contract must specify who obtains each permit and what happens if a permit is delayed or denied:
| Permit | Typical Responsibility | Notes |
|---|---|---|
| Building permit | Contractor | Includes structural, architectural drawings |
| Plumbing permit | Plumbing subcontractor | Separate from building permit |
| Electrical permit | Electrical subcontractor | Separate ESA permit and inspection |
| HVAC permit | HVAC subcontractor | May be combined with building permit |
| Fire separation certificate | Contractor/Fire Inspector | Required for occupancy |
If the contractor is responsible for permits, the contract should state that permit fees are included in the price and that delays in permit issuance extend the completion date.
Warranty Stacking
With multiple trades involved, warranties stack:
| Trade | Component | Labour | Material |
|---|---|---|---|
| General | Workmanship | 2 years | 5 years |
| Plumbing | Piping, fixtures | 2 years | 5 years |
| Electrical | Wiring, panel | 2 years | 5 years |
| HVAC | Equipment, ductwork | 2 years | 5 years |
| Waterproofing | Membrane (if applicable) | 5 years | 25 years |
| Structural | Underpinning (if applicable) | 10 years | Lifetime |
Your contract should list each trade's warranty separately. If a plumbing leak damages drywall, you need to know which warranty covers what.
Fire Separation and Life Safety
Ontario Building Code requires:
Your contract should explicitly reference these requirements and include inspection milestones for each.
Common Basement Apartment Disputes
The most frequent disputes on basement apartment projects:
A detailed contract with milestone-based payments prevents most of these disputes. For each, the contract should specify the resolution mechanism before work begins.
Contract Must-Haves for Basement Apartments
Beyond the standard CPA requirements, include:
For current pricing on basement apartment conversions, see our [Cost Guide](/costs/basement-second-unit) or our [Basement Second Unit Service Page](/services/basement-second-unit).
Generate a complete basement apartment contract with our free [Contract Generator](/contracts).
