How do you calculate project costs?

We use current market rates for high-quality materials and skilled labour in Durham Region. Every estimate includes a detailed breakdown of tasks so you know exactly where your money is going.

Is the initial consultation free?

Yes. We offer a free first meeting to look at your space and talk about your goals. After that we provide a clear price range for your specific project.

Do you offer fixed-price contracts?

Most of our projects use fixed-price contracts. This means the price we agree on is the price you pay, unless you decide to change the scope of work later.

What happens if material prices go up?

Once we sign a contract, we lock in the material prices for you. We order supplies early to make sure your budget stays safe from market changes.

How long will my renovation take?

Small jobs might take two weeks, while large additions can take months. We give you a full schedule before we start so you can plan your life around the work.

Will I have a dedicated project manager?

Yes. You will have one main person to talk to. They will be on site often to check quality and keep you updated on our progress every day.

How do you keep the job site clean?

We clean up at the end of every single day. We use floor protection and dust barriers to keep the rest of your home safe and tidy while we work.

Do I need to move out during construction?

For most room renovations you can stay home. For very large projects like whole-home guts, we might suggest staying elsewhere for a short time for your comfort.

What areas do you serve?

We serve all of Durham Region including Oshawa, Whitby, Bowmanville, Ajax, Pickering, Newcastle, Clarington, Scarborough, Stouffville, and Peterborough.

Do you handle permits and inspections?

Yes. We submit the plans to the municipality, get the permits, and schedule all required inspections to ensure your home is safe and the work is done to code.

Can you help with the design phase?

Yes. We work with designers and architects to help turn your ideas into professional drawings before we start building.

Do you do commercial construction?

Yes. We offer commercial services for offices, retail spaces, and restaurants alongside our residential renovation work.

What kind of warranty do you provide?

Every Cornerstone project is backed by a 5-year written workmanship warranty. If something we built fails because of how it was installed, we fix it at no charge.

What if I find a problem after you leave?

Contact us directly. We respond to warranty concerns within 1 to 2 business days and will schedule a site visit to assess the issue at no cost to you.

Are you insured and WSIB compliant?

Yes. Cornerstone Construction carries full liability insurance and all our workers are covered by WSIB. This protects you and your home completely.

Do you offer maintenance tips?

Yes. At the end of every project you receive a full Owner's Manual with care and maintenance instructions for every material and system we installed.

BowmanvilleCourticeNewcastle

Legal Basement Apartment in Clarington

Can you legally rent out your basement in Clarington? Yes — in Bowmanville, Courtice, Newcastle, all of it. A legal suite can help pay your mortgage. Or house family. But one local rule quietly stops most DIY plans. We know it. We build around it. Here's what Clarington asks for, in plain words.

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

The Catch Most People Miss

You Can't Just Pave the Lawn for Parking

Clarington protects front-yard greenery: at least 30% of your front yard has to stay soft landscaped — grass, sod or planting. (It can be higher in some zones — we confirm your exact number.) So the instinct to widen the driveway for the tenant's parking space often breaks the rule that legalizes the suite. It's the single most common thing that stalls a DIY Clarington basement — and it's why the parking layout has to be planned before a dollar is spent.

Rule Book 1 · Clarington Zoning

What Your Property Has to Clear

These are the local rules a Clarington home must satisfy to add a legal Additional Dwelling Unit. We check every one before designing.

Parking — One Space Per Suite

Your home needs its two existing spaces, plus one more for the ADU. Clarington permits tandem parking (one car behind another), so many driveways already qualify — as long as it doesn't block the sidewalk.

Front-Yard Landscaping (the catch)

At least 30% of the front yard must stay soft landscaped — which is why you often can't just pave for parking. We plan the parking and access around it so the layout actually passes.

Up to Two Units

Most Clarington properties can add up to two ADUs, subject to your zone and lot. Some lots on the Oak Ridges Moraine carry extra limits — we confirm your property's status early.

A Safe, Separate Entrance

The suite needs its own entrance with a clear, unobstructed path of travel — designed into the plan from day one so emergency access and code clearances are covered.

A legal suite is fully self-contained — its own kitchen and bathroom, built to the standard of our kitchen renovations in Bowmanville, Courtice and Newcastle, with the same structural and beam work we use to open up a basement.

How It Works

We Handle the Municipality. You Don't.

Building the suite is only half of it — Clarington requires every ADU to be registered. We carry the whole thing, from the landscaping math to the registration.

What We Handle

Confirm your zone, parking feasibility and the 30% landscaping rule
Design and scaled drawings to the Municipality's standards
File the building permit and the ADU registration
Build to code — fire separation, egress, plumbing, electrical
Pass every inspection through to final occupancy
Register the unit ($260 application & registration fee, HST-exempt)

Your Part

Book the free diagnostic
Choose your finishes
Check in through your portal
Collect the rent

Rule Book 2 · Inside the Suite

What the Building Code Requires

Inspectors in Bowmanville, Courtice and Newcastle check these closely at the framing and final inspections. They're the same across Ontario — here's what matters most in a basement:

The Essentials

Ceilings at least 1.95 m (6 ft 5 in), dropping to 1.85 m under beams. Where the open floor is lower, the floor can be lowered to pass.
An escape window in every bedroom, sized to climb out of in a fire, with clearance in the window well.
A 30-minute fire separation between your suite and the home above.
Interconnected smoke and carbon-monoxide alarms — one sounds, they all sound.
Minimum room sizes so the space is genuinely livable.

See the full room-by-room size table in our Durham guide

Why Build It Legal

A Registered Suite Is Worth More

Real Income

A registered suite rents with confidence and carries a real chunk of your mortgage across Clarington.

Insurance & Resale

A registered unit is what insurers and buyers want to see. An undisclosed one can void coverage.

Tenant Safety

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

No Surprises

Built and registered once, properly — no retroactive enforcement, no forced rework, no order to vacate.

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 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 the two your main house needs. Clarington allows tandem parking (one car behind another in a single-lane driveway), so many driveways already qualify, as long as it doesn't block the sidewalk. The catch: you can't widen the driveway to add it if that drops your front-yard soft landscaping below the minimum.

What's this landscaping rule?

Clarington requires at least 30% of your front yard to stay as soft landscaped space — grass, gardens or sod (it can be higher in some zones). It stops owners paving over the whole lawn for parking, and it's the rule that most often limits where the tenant's space can go. We plan the parking and access around it so the layout passes.

Does the suite have to be registered?

Yes. Clarington requires every ADU to be registered with the Municipality — it's confirmed once the building inspector grants occupancy, and the application & 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 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, the 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 fee information last reviewed July 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; Zoning By-law 84-63 (and 2005-109 for Oak Ridges Moraine lands); User Fee By-law 2026-021 (ADU application & registration $260); Ontario Building Code.

Part of Our Durham Legal Suites Guide

See requirements for every Durham town, plus the full second-suite overview

Back to Hub →

Also building legal suites in Oshawa, Whitby, and across Durham Region.

Before You Widen That Driveway — Let's Check

Start with a free basement check. We'll test your parking and yard against the rules first, measure your ceiling and egress, and give you a clear, locked price. No surprises, no torn-out work later.