Experts for Home Addition in Toronto and the GTA
Second Storey Home Additions, Rear Extensions & More
Home Additions in Toronto & The GTA
A well-designed home addition keeps you in the neighbourhood you’ve chosen, on the lot you already own, and almost always returns more on the dollar than a comparable spend on relocation.
At Grand Design Build, we’ve designed and built additions across Toronto, North York, Forest Hill, Rosedale, Etobicoke, Oakville, Mississauga, and Thornhill since 2010. Second storeys above existing bungalows. Rear extensions that reshape how a main floor lives. Side additions, dormers, garage builds, and basement underpinning to add full-height space below grade. Every project is delivered under a fixed-price contract, with permits handled in-house and a dedicated coordinator running the schedule from the first site visit through to handover.
Our Service Includes:
- Indoor-outdoor living spaces
- Operative rooftop terraces
- All-weather decks for dining and entertaining
- Additional bedrooms
- Expanding or adding ensuites Kitchen and dining area
If you’re weighing whether to add on or move, we’ll give you a straight answer at the consultation.
Our Home Addition Projects
Types of Home Additions We Build in Toronto And The GTA
Not every home needs the same kind of addition. The right approach depends on your lot, your existing structure, your municipality’s zoning rules, and what the addition is actually for. A family adding two bedrooms has different options than a homeowner trying to widen a narrow main floor. We’ve built all of it.
Second Storey Addition
The most impactful way to double your living space. A full second storey addition adds bedrooms, bathrooms, and flex space above your existing footprint, without touching your lot. Ideal for growing families in established Toronto neighborhoods where lots are too valuable to build out on.
Rear Addition
Extend your main floor into the backyard. Rear additions are one of the most common ways Toronto homeowners expand their kitchen, dining area, or family room. They integrate seamlessly with your existing layout and are often the most cost-effective way to add significant square footage.
Side Addition
When lot width allows, a side addition expands your home laterally. Often used to widen a narrow main floor, add a mudroom, or create a more generous entryway. Works particularly well in semi-detached homes where one side is exposed.
Dormer Addition
A targeted way to add usable headroom and light to an existing upper floor without a full second storey build. Cost-effective, minimally invasive, and effective in attic conversions or semi-finished upper levels.
Garage Addition
Expand or add garage space on your property. Whether you need a second bay, a heated workshop, or a structure that doubles as a studio or guest suite above, we design garage additions that serve multiple purposes.
Basement Extension & Underpinning
Lowering and reinforcing an existing foundation to create a full-height, functional basement. We manage excavation, structural engineering, waterproofing, and interior finishing, everything from underpinning to the finished ceiling.
How to Choose a Home Addition Contractor in Toronto
Not every general contractor is qualified to build an addition; additions involve structural engineering, foundation work, and roofline integration that general construction experience doesn’t cover. Before hiring a home addition contractor in Toronto, verify these fundamentals:
- HCRA licensed: Ontario requires this for major additions by law. Ask for the registration number and verify it on the Ontario Builder Directory.
- Fixed-price, not cost-plus: A fixed-price contract caps your risk before work starts. Cost-plus leaves your bill open-ended as costs rise.
- Structural warranty offered: Work with a contractor who offers structural warranty as it safeguards your home against any issues that might arise in the future.
- Permits handled in-house: Toronto additions require permits, full stop. Your contractor should manage the application and zoning process for you, not leave you to it.
Why Homeowners in Toronto Choose Grand Design Build
Fixed-price contracts: Your number is set before construction starts and doesn’t move unless the scope does. that accounts for the full scope of work.
HCRA licensed: Grand Design Build is licensed by the Home Construction Regulatory Authority of Ontario, a legal requirement for builders doing this type of work.
7-year structural guarantee: Every home addition is backed by a 7-year structural guarantee, which is longer than most builders in this market are willing to commit to.
In-house design and permits: We handle architectural drawings, permit applications, and zoning compliance in-house. No coordinating between a designer, a permit consultant, and a builder.
Dedicated project coordination: Every project has a dedicated coordinator who manages the schedule, the trades, and the communication. You always know what’s happening and what’s next.
Operating since 2010. Over a decade of additions, extensions, and structural builds across Toronto, North York, Forest Hill, Rosedale, Etobicoke, Oakville, and Mississauga.
How a Home Addition Starts At Grand Design Build
Complimentary Consultation
Set up a meeting within one business day. We will walk through your goals, take measurements, and review existing conditions. For larger projects we'll bring our designer and a structural estimator. This is free and carries no obligation.
Proposal & Scope
We produce a preliminary proposal, a detailed scope document, and a fixed-price structure broken down by line item. You know exactly what's included, what isn't, and what each component costs before you commit. Review it, ask questions, request changes, we'll rescope as needed.
Drawings & Permits
Our in-house architects and designers create your custom blueprints. We manage the entire City of Toronto permit application process, including architectural drawings, structural engineering, and navigating any required zoning variances.
Build & Inspections
We start building your dream home based on the approved designs and contract. Our team and municipal authorities conduct thorough inspections at every milestone to ensure full compliance with the Ontario Building Code and project specifications.
Handover & Warranty
The moment your vision becomes a reality. We conduct a final walkthrough to ensure your total satisfaction and seamlessly transition the new home into your possession, all backed by our 7-Year Structural Guarantee.
READY TO DISCUSS YOUR PROJECT?
What Our Clients Say About Our Services
We Offer Home Building Services In Toronto
Your home is one of the biggest investments you’ll ever make. Whether you’re building a custom home, adding space with an addition, transforming your space through a renovation, or maximizing your property with a laneway suite, you deserve a builder you can trust to get it right.
At Grand Design Build, we’ve spent over 15 years earning that trust. Through meticulous planning, honest pricing, and efficient construction, we deliver exceptional results without the stress, surprises, or budget creep that too often come with the territory. Every project, no matter the size, is backed by our guarantee, because we don’t just build homes. We stand behind them.
Frequently Asked Questions
What Does a Home Addition Cost in Toronto?
For a fully finished, permitted one-storey addition, budget $300–$500 per sq ft. A 400 sq ft rear extension typically lands between $120,000 and $200,000 depending on site conditions and finishes. Second storey additions generally start at $350–$450 per sq ft given the additional structural work involved. Professional fees, architecture, engineering, permits, add roughly 10–15% on top. For a full breakdown, read our Home Addition Cost Guide.
Do I need a permit for a home addition in Toronto?
Yes. All home additions in Toronto require a building permit. This includes second storey additions, rear extensions, side additions, and basement underpinning. Grand Design Build manages the full permit process, including drawings, application submission, and inspections.
How long does a home addition take?
Most home additions take between 6 and 12 months from signed contract to handover. The timeline depends on the scope of work and the permit review period. Second storey additions typically take longer than rear additions. We provide a detailed construction schedule before work begins.
Can I stay in my home during the addition?
In most cases, yes, though there will be periods of disruption, particularly when structural work is underway or when the roof is open during a second storey build. We plan phasing to minimize disruption and give you advance notice of the most intensive periods.
What is the difference between a home addition and a home extension?
The terms are used interchangeably. Both refer to adding new square footage to an existing home by building outward (rear or side extension) or upward (second storey addition).
Does Grand Design Build handle zoning and setback requirements?
Yes. Our in-house design team reviews zoning bylaws, lot coverage limits, and setback requirements before we finalize any design. We flag potential issues early so they don’t become problems during permitting.
What makes Grand Design Build different from other home addition contractors in Toronto?
Three things:
- We’re HCRA licensed (required for this type of structural work in Ontario)
- We offer fixed-price contracts (your quote is your price)
- We back every addition with a 7-year structural guarantee.
Most contractors offer none of these. We offer all three.