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.

Additions & Garages Ajax · Additions & Garages

Home Additions & Garages in Ajax

Ajax's zoning by-law runs on dozens of numbered exceptions tied to specific subdivisions, not one town-wide setback rule. What's allowed next door isn't automatically allowed on your lot. We confirm exactly which zone and exception applies to your property before we design anything.

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

Ajax at a Glance

60m²Max ground floor area for a detached accessory dwelling unit

ManyNumbered exception zones under By-law 95-2003, each with its own rules

No flatPermit fee — Ajax emails your exact fee after a completeness pre-screen

$2-4kPer-unit grant available for eligible additional dwelling unit projects

Before We Design Anything

The Rules That Actually Matter

Ajax's Zoning By-law 95-2003 covers the whole town, but dozens of numbered exceptions override the base zone rules for specific subdivisions and plans of subdivision. Two houses on the same street, in different exception zones, can have genuinely different setback and garage-width rules.

Setbacks & Lot Coverage

Base zones (R1, R2, R3) set standard setbacks, but numbered exceptions can override them for specific plans of subdivision — some allow interior side yards as tight as 0.0m to 1.2m, others require a minimum 5.5m setback for an attached garage.
Maximum garage width can also vary by zone — some R2 zones cap garage width at 5.0m on narrower lots.
Ajax permits up to three accessory dwelling units per lot (four dwellings total), with at most one detached — subject to size, height, and setback rules plus a building permit.
A detached accessory dwelling caps at 60m² ground floor area and must be smaller than your main house's footprint.

What Needs a Permit

Additions, garages, basement finishing, and any structural, plumbing, electrical, or HVAC change all require a building permit.
Ajax doesn't publish a flat permit fee schedule — the Town emails your exact fee after a completeness pre-screen of your application, under Building Permit Fee By-law 48-2023.
Eligible additional dwelling unit projects may qualify for the Town's "Build More, Get More" grant — roughly $2,000 to $4,000 per unit, up to $12,000.
Ajax's Committee of Adjustment can grant a minor variance if your project falls just short of a setback rule.

If your addition includes a basement or a secondary suite, see our legal basement apartment guide for Durham Region — the parking and unit-count rules there are separate from what applies to a straight addition or garage.

Building Up

What a Second-Storey Addition Actually Requires

Adding a full floor on top of your existing home isn't just framing walls — it changes the structure underneath it too.

What's Involved

Full roof removal down to the existing top plate before the new floor goes on.
A new engineered floor system spans where the roof used to be — this becomes your new upper floor.
The ceiling on your existing main floor gets disturbed by this work and needs refinishing once the new floor system is in.
Structural engineering confirms your existing walls and foundation can actually carry the new load — not optional, required on every second-storey build, and covered under our BCIN design & permit drawing services.
Most Ajax homes built post-1990 have a straightforward framing profile to build on top of — we confirm your home's specifics at the site visit before finalizing a design.

See real pricing for second-storey additions in our investment calculator

How It Works

Zoned, Designed, Permitted, Built

An addition isn't just built — it's checked against your specific zone and exception, engineered, permitted, and inspected. We carry all of it.

Confirm Your Zone & Exception

We identify your base zone and check whether a numbered exception under By-law 95-2003 overrides the standard setbacks for your property.

Design & Engineered Drawings

Scaled plans plus structural engineering where required — mandatory for any second-storey work.

Building Permit

Filed with the Town. Since Ajax doesn't publish a flat fee, we get your exact quote from the completeness pre-screen before committing you to a number.

Build & Inspections

Framing, structural, electrical, and plumbing inspections through to final sign-off.

$300

Our on-time guarantee. If we miss the agreed completion date for reasons within our control, you're compensated $300 for every day past it — part of the Certainty Stack on every Cornerstone build.

Why Build It Permitted

A Permitted Addition Is Worth More

Resale Confidence

A permitted addition shows clean on a title search. An unpermitted one can hold up your sale or force disclosure to buyers.

Insurance Stays Valid

Unpermitted structural work can void your coverage if something goes wrong down the line — permitted work protects your policy.

No Forced Teardown Risk

The Town can order unpermitted additions removed or brought up to code after the fact. Done right the first time, that risk doesn't exist.

Built to Carry the Load

Proper engineering means your addition holds up for decades — not just long enough to pass a first inspection.

Common Questions

Ajax Addition & Garage FAQ

Do I need a permit for a home addition in Ajax?

Yes. Additions, garages, basement finishing, and any structural, plumbing, electrical, or HVAC change all require a building permit through the Town of Ajax. We handle the application and coordinate every inspection.

Why doesn't Ajax have one standard setback for garages?

Ajax's Zoning By-law 95-2003 includes dozens of numbered exceptions tied to specific plans of subdivision. Two properties on the same street can fall under different exceptions with genuinely different setback and garage-width rules. We confirm exactly which zone and exception applies to your property before designing anything.

How much will my Ajax building permit cost?

Ajax doesn't publish a flat fee schedule for building permits. The Town reviews your application for completeness first, then emails your exact fee under Building Permit Fee By-law 48-2023. We get that real number before committing you to a budget.

Can I build a detached accessory dwelling unit on my property?

Ajax allows up to three accessory dwelling units per lot (four dwellings total), with at most one detached. A detached unit caps at 60m² of ground floor area and must be smaller than your main house's footprint. Eligible projects may also qualify for the Town's "Build More, Get More" grant.

Can I convert my existing garage into living space instead of building new?

Yes — this falls under Space Conversion rather than new construction, since there's no new foundation or exterior envelope to build. It's a genuinely different scope and cost than a new addition or a new garage build.

What happens if my addition doesn't fit my zone's setback rules?

Ajax's Committee of Adjustment can grant a minor variance if your project falls just short of a setback or coverage rule. We flag this early rather than after drawings are done, so you know your real options before committing to a design.

Zoning and permit information last reviewed September 2026. Municipal requirements can change — Cornerstone confirms current Town of Ajax requirements with Planning and Building Services on every project. Sources: Town of Ajax Zoning By-law 95-2003 and its numbered exceptions; Town of Ajax Building Permit Fee By-law 48-2023.

Part of Our Durham Additions & Garages Guide

See our full investment calculator, garage attached vs. detached breakdown, and FAQ

Back to Additions & Garages →

Also building additions and garages in Whitby, Oshawa, and across Durham Region.

Thinking About an Addition or Garage in Ajax?

Start with a free project diagnostic. We'll check your exact zone and exception, run the real numbers, and give you a clear, locked price. Built once, built right.