ADUs & Garage Conversions
Your Property.
More Value.
More Options.
Accessory dwelling units, garage conversions, and detached suites built to code and designed to generate income or house family. Eastern Ontario’s experienced ADU builder.
25+
Years Experience
30+
ADUs Completed
$1,800+
Avg. Monthly Rental
4.8★
Google Rating
What We Build
Income suites, in-law units, and detached cottages, permitted and built properly.
Ontario’s housing policy has shifted significantly in favour of secondary units on residential lots. What used to require variances and committee hearings is now largely as-of-right zoning in most municipalities. If you have a garage, a large basement, or room on your lot, there’s a real opportunity here. We’ve built over 60 of these units across Northumberland County. We know the process, the permit requirements, and how to build a unit that actually generates income and holds its value.
Recent Work
The Process
From feasibility to finished unit
01
Feasibility Review
We review your lot, existing structure, and municipal zoning to tell you exactly what’s buildable and what it’ll cost.
02
Design & Permits
We design the unit around rental marketability, handle all permit applications, and navigate secondary suite bylaws.
03
Build
One crew, one manager, fixed timeline. Mechanical, electrical, and plumbing all in-house: no subcontractor delays.
04
Inspection & Handover
Municipal inspection handled. Unit delivered tenant-ready. You start generating income from day one.
Est. 1999
Family-Owned
Why Cobourg Construction
We’ve built over 60 ADUs. We know what renters want and what municipalities require.
There’s a real difference between a secondary unit that passes inspection and one that commands top-of-market rent. The layout matters. The finishes matter. The soundproofing matters. We build units that are easy to rent and hold their value long-term.
And because we handle permits in-house, you’re protected. An illegal unit is a liability. A properly permitted ADU is a long-term asset that adds to your property value and qualifies for rental income programs.
Frequently Asked Questions
What does an ADU cost to build in Northumberland County?
Accessory dwelling units start at $280 per square foot. A 700 square foot garden suite therefore starts around $196,000. Garage conversions usually cost less because the structure and foundation already exist.
Are ADUs legal in Cobourg and Port Hope?
Yes. Ontario permits additional residential units on most residential lots, subject to local zoning, servicing and setback rules. We confirm what your specific property allows before design begins.
Can an ADU pay for itself?
Many do. A garden suite or converted garage generates rental income, houses a family member, or adds resale value. There is also a federal Multigenerational Home Renovation Tax Credit for building a self-contained suite for a relative aged 65 or over, or an adult with a disability.
Ready to add a suite?
Tell us about your property. We’ll tell you what’s buildable, what it’ll cost, and what you can expect to rent it for.