Bowmanville · Courtice · Newcastle

Legal Basement Apartment
in Clarington

Bowmanville, Courtice, Newcastle and across Clarington — here's exactly what the Municipality and the Ontario Building Code require to make your basement apartment legal, and how Cornerstone gets it permitted, inspected, and registered.

Start Your Basement Diagnostic Call 1-888-404-7383

The Two Rule Books

What Makes a Basement Apartment "Legal" in Clarington

In Clarington a second suite is an Additional Dwelling Unit (ADU). To be legal it has to satisfy both the Municipality's zoning and registration rules (parking, landscaping, registration) and the Ontario Building Code (room sizes, ceiling height, fire separation and safe exits). Clarington has expanded ADU permissions to support more housing — but the suite still has to be built and registered to the rules.

Clarington Zoning & Registration

Sets the outside rules: parking, front-yard landscaping and a mandatory ADU registration — under Clarington's Zoning By-laws, as amended for ADUs.

Ontario Building Code

Sets the inside rules: minimum room sizes, ceiling height, egress windows, a 30-minute fire separation and interconnected alarms.

Rule Book 1

Clarington Zoning Requirements

These are the property-level rules a Clarington home must satisfy to add a legal Additional Dwelling Unit.

Parking — One Space, Tandem Allowed

  • You must provide one designated off-street parking space for the ADU, in addition to what the main dwelling requires.By-law 2024-033, amending 84-63 §3.16
  • Tandem parking is permitted — the ADU's space can sit one car behind another in the driveway, as long as it doesn't obstruct a municipal sidewalk or boulevard.
  • That tandem allowance means many existing Clarington driveways already satisfy the parking rule without changes.

The Front-Yard Landscaping Catch

  • Clarington protects green space: a minimum of 35% of the front yard must stay as soft landscaped open space — grass, sod or planting.By-law 84-63, §12
  • This is the rule that trips people up: you cannot simply widen the driveway or pave over the lawn to add the tenant's parking space if doing so drops your front-yard greenery below that 35% minimum.
  • It's exactly why the parking layout has to be planned properly from the start — which is what we do before committing to a design.

Entrance Access

  • An unobstructed path of travel must be maintained to the suite's side or rear entrance, subject to your lot's local zoning setbacks.
  • We design the entrance and walkway into the plan so emergency access and code clearances are covered from day one.

Rule Book 2

Ontario Building Code: Inside the Suite

A Clarington building inspector verifies every measurement against the Ontario Building Code before granting final occupancy. These numbers apply Province-wide, in Clarington the same as anywhere in Ontario.

Minimum Room Sizes

RoomMinimum Floor Area
Living Room13.5 m² (145 ft²)May reduce to 11 m² if combined with other space in a one-bedroom unit.
Kitchen4.2 m² (45 ft²)May reduce to 3.7 m² in a one-bedroom unit.
Dining Room7.0 m² (75 ft²)May reduce to 3.25 m² if combined with another room.
Primary Bedroom9.8 m² without a closet, or 8.8 m² with a built-in closet.
Additional Bedrooms7.0 m² without a closet, or 6.0 m² with a closet.
BathroomSelf-contained — toilet, sink and tub/shower with proper clearance.

Egress Windows

  • Every bedroom needs an egress window with a minimum unobstructed opening of 0.35 m², with no single dimension less than 380 mm.OBC 9.9.10.1.(1)(b)
  • Where that window opens into a below-grade window well, the Code requires a clearance of at least 550 mm in front. We often build deeper than the minimum so an outward-swinging sash never blocks the escape path.OBC 9.9.10.1.(5)

Ceiling Height

  • The finished ceiling must be at least 1.95 m (6 ft 5 in) across the habitable space.OBC 9.5.3.1
  • It may drop to 1.85 m (6 ft 1 in) only under localized obstructions — beams, structural columns or boxed ductwork. Where the open floor is below 1.95 m, the floor may need lowering (underpinning or bench footing) to pass.

Fire Separation & Alarms

  • The floor/ceiling and walls separating the suite from the main home must form a continuous, smoke-tight fire separation with a minimum 30-minute fire-resistance rating. A typical way we achieve this is mineral wool packed in the joist cavities with two continuous layers of 5/8" Type X drywall on resilient channels — one tested method that meets the requirement.OBC 9.10.9.14
  • Smoke alarms are required on every storey of both units and must be fully interconnected — if one sounds in the basement, every alarm in the house above sounds at the same time. Carbon monoxide alarms are required as well.OBC 9.10.19

Permit & Registration

How a Legal Suite Gets Approved in Clarington

Building the suite to code is only half of it. Clarington requires every ADU to be registered with the Municipality — and registration confirms the unit is safe and conforms to zoning.

Confirm Your Property

We check your zone, parking feasibility and the 35% front-yard landscaping rule before committing to a layout.

Design & Drawings

Scaled drawings showing existing and proposed floor plans, room areas, egress, fire separation and alarm locations — prepared to the Municipality's submission standards.

Building Permit & ADU Registration

The building permit is submitted and the unit is registered with Clarington. The Additional Dwelling Unit application and registration fee is $260 (exempt from HST).

Build & Inspections

We build to code and pass every required inspection — fire separation, egress, plumbing and electrical — through to final sign-off.

Occupancy & Registration Confirmed

Once inspections clear and fees are paid, the unit is a registered, legal ADU — which protects your insurance and helps at resale.

Clarington ADU application & registration fee: $260 (exempt from HST), per the Municipality's current fee schedule, plus the standard building permit fees based on the work. Registering it properly is what keeps your suite legal, insurable and free of enforcement risk.

Why Build It Legal

A Registered Suite Is Worth More

Real Rental Income

A legal, inspected suite can be rented with confidence — and a second unit can carry a real chunk of your mortgage across Bowmanville, Courtice and Newcastle.

Insurance & Resale

A registered suite is what your insurer and a future buyer want to see. An undisclosed unit can void coverage and scare off buyers.

Tenant Safety

Code-built fire separation, egress windows and interconnected alarms keep the people living there safe — and keep you out of liability.

No Surprises Later

Built and registered once, properly, means no retroactive enforcement, no forced rework, and no order to vacate down the road.

Common Questions

Clarington Basement Apartment FAQ

Do you build legal suites in Bowmanville, Courtice and Newcastle?
Yes — all three are part of the Municipality of Clarington, so the same Clarington zoning and registration rules apply across Bowmanville, Courtice, Newcastle and the surrounding area. We build and permit legal basement apartments throughout Clarington.
Do I need extra parking for a basement apartment in Clarington?
Yes — one designated off-street space for the ADU, on top of what the main house needs. Clarington permits tandem parking (one car behind another), so many driveways already qualify. The catch: you can't widen the driveway to add it if that drops your front-yard soft landscaping below the 35% minimum.
What's this 35% landscaping rule?
Clarington requires at least 35% of your front yard to stay as soft landscaped open space — grass, sod or planting. It protects neighbourhood greenery, and it's the rule that most often limits where the tenant's parking space can go. We check it before designing so the parking plan actually works.
Does the suite have to be registered?
Yes. Clarington requires every ADU to be registered with the Municipality, which confirms the unit conforms to zoning and the Building Code. The application and registration fee is $260 (exempt from HST). Registration is what keeps the suite legal and insurable.
My basement ceiling feels low — is that a dealbreaker?
Not necessarily. The Code requires 1.95 m (6 ft 5 in) across the habitable space, dropping to 1.85 m only under beams, columns and ducts. Many Clarington basements qualify; where the open floor is below 1.95 m, lowering the floor (underpinning or bench footing) can solve it. We measure this early so there are no surprises.
What affects the cost of a legal basement apartment?
Ceiling height and whether the floor needs lowering, a separate entrance, egress windows and wells, the kitchen and bathroom layout, the 30-minute fire separation, and electrical/HVAC separation all drive cost. After a site visit we give you a clear, locked scope and price — not a guess.
Bylaw and code information last reviewed June 2026. Municipal requirements and fees can change — Cornerstone confirms current Municipality of Clarington requirements with Planning and Building Services on every project. Sources: Municipality of Clarington Additional Dwelling Units page and ADU registration; Zoning By-laws 84-63 and 76-24 (as amended for ADUs, By-laws 2021-082 / 2024-033); User Fee By-law 2026-021; Ontario Building Code (O. Reg. 332/12) sections 9.5.3.1, 9.9.10.1, 9.10.9.14, 9.10.19.
Part of Our Durham Legal Suites Guide
See requirements for every Durham town, plus the full second-suite overview
Back to Legal Suites
Legal Basement Apartments Across Durham
We also build legal second suites in nearby Oshawa, Whitby, and across Durham Region.

Thinking About a Legal Basement Apartment in Clarington?

Start with a basement diagnostic. We'll confirm your parking and landscaping, measure your ceiling and egress, and map out the path to a legal, registered suite in Bowmanville, Courtice or Newcastle — built once, built right.

Start Your Basement Diagnostic Call 1-888-404-7383

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