MINI DANT Homes by DANT Homes Inc.: The Complete Step-by-Step Guide to Building an ADU in Ontario

Everything homeowners need to know from consultation to move-in.

As cities across Ontario continue to face housing shortages and rising home prices, more homeowners are exploring Accessory Dwelling Units (ADUs)—also known as garden suites, coach houses, and secondary suites.

These small, self-contained homes offer extra living space, rental income, or a comfortable place for family to live close by.

If you’re thinking about building an ADU, here’s a clear, homeowner-friendly guide to the entire process.

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1. Initial Consultation: Understanding Your Vision and Your Lot

Every successful ADU project starts with a conversation.

During the initial consultation, your builder will typically:

Review your property layout, lot size, zoning, and setbacks
Discuss your goals—rental income, multigenerational living, downsizing, or adding value
Explore potential locations for the unit
Look for servicing access (water, sewer, electrical)
Provide a rough cost range and expected timeline

This is also the stage where you can ask questions about:

What size ADU you can build
Whether your existing utilities can support a new unit
Parking, landscaping, and privacy considerations

A good consultation sets expectations early and ensures you understand what’s possible before moving to design.

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2. Design: Turning Ideas Into a Buildable Plan

Once the project moves forward, the next stage is design and architectural planning.

Design includes:

Concept Plans
Basic layouts showing the footprint, room sizes, windows, and key features.
Architectural Drawings
Fully detailed drawings required for permit submission, including floor plans, elevations, foundation plans, roof plans, and building sections.

Engineering

Depending on your municipality and build type, engineering may include:

Structural engineering
Grading and drainage plans
HVAC and mechanical design
Energy efficiency calculations

Customization

At this stage, you’ll choose:

Finishes
Exterior materials
Window styles
Layout preferences
Accessibility options (wider doors, ramps, walk-in showers, etc.)

A well-designed ADU balances comfort, function, privacy, and long-term durability.

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3. Permits: Navigating Municipal Requirements

Permitting is often the most misunderstood part of building an ADU, but it’s essential to get right.

Typical permits and documents include:

Building Permit (the main approval)
Site Plan / Grading Plan
Zoning Review
Utility service approvals if upgrades or trenching are required
HVAC/Mechanical Permit
Electrical Notification (via ESA in Ontario)

Your builder or designer will prepare and submit the full package, including:

Architectural drawings
Structural engineering
Lot coverage calculations
Drainage plans
Energy compliance reports

Approval times vary, but most municipalities take 4–10 weeks, depending on workload and complexity.

Once permits are approved, construction can begin.

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4. Construction: Building the ADU

With permits in hand, the physical build starts.

Construction generally follows these phases:

Site Preparation

Excavation (often required for foundations and servicing trenching)
Grading adjustments
Access preparation for equipment

Foundation

Options include:

Slab-on-grade
Crawlspace
Full basement
Helical piles (for certain designs)

Framing

The unit takes shape with:

Floors
Walls
Roof structure

Rough-Ins

Essential systems are installed:

Plumbing
Electrical
HVAC
Sewer connections
Water and hydro trenching (if needed)

Insulation & Drywall

Energy-efficient insulation is installed, followed by drywall boarding and taping.
Interior Finishes

This is where the ADU feels like a home:

Flooring
Trim and doors
Cabinets
Plumbing fixtures
Appliances
Painting

Exterior Work
- Siding
- Roofing
- Landscaping
- Decks, patios, or walkways

Throughout this phase, your builder manages trades, inspections, quality control, and scheduling.

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5. Inspections: Ensuring Safety and Compliance

Inspections happen at several stages to ensure everything meets the Ontario Building Code.

Typical inspections include:

Footings and foundation
Framing
Plumbing and electrical rough-ins
HVAC rough-in
Insulation and air barrier
Final inspection for occupancy

If anything needs adjustment, your builder will correct it promptly before re-inspection.

Once the final inspection is completed and the city approves the work, you receive occupancy clearance.

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6. Move-In: Your New Space Is Ready

After approvals, it’s time to enjoy your new ADU.

Homeowners typically use ADUs for:

Rental income to offset mortgage costs
A suite for aging parents
Space for adult children
A long-term investment in property value
A private home office or studio

Your builder will provide a walkthrough to review:

How to operate mechanical systems
Warranty Information
Maintenance recommendations
Emergency shut-off locations

This ensures you feel confident and comfortable in your new unit from day one.

Final Thoughts

Building an ADU in Ontario is one of the smartest ways to add usable space and long-term value to your property. The process—from consultation to move-in—is well-defined, and with the right builder, it’s smooth and predictable.

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