Home Additions & Second Storeys in Greater Toronto Area
Home additions and second storeys are the biggest renovation projects most homeowners will ever take on. This covers rear or side extensions, bump-outs for kitchens and family rooms, full second-storey additions on a bungalow, and in-law suites over a garage. Unlike a kitchen refresh or a bathroom remodel, this work touches the structure of the house: foundations, framing, roof lines, and often the electrical and mechanical systems too. It also means dealing with the city or region on permits, zoning setbacks, and in older Toronto neighbourhoods, sometimes committee of adjustment approval for variances.
We've listed 49 companies in the GTA that take on this kind of work, ranging from framing-focused builders to full design-build firms that handle architectural drawings, engineering, permits, and construction under one contract.
What to look for before you sign anything
- A structural engineer's stamp on the drawings, not just an architect's sketch
- A clear breakdown of who pulls the building permit and who covers any structural engineering costs
- Experience with your specific project type: a second storey on an existing foundation is a different risk profile than a ground-floor addition on new footings
- A written schedule with rough milestones (framing, roof close-in, mechanical rough-in, drywall) so you can track delays
- References from a project completed at least a year ago, so you can ask about how the house performed through a full season
Our scoring weighs how a company handles the parts homeowners can't easily judge themselves: licensing and insurance, permit history, how disputes and warranty callbacks get resolved, and the consistency of past client feedback. See the full breakdown on our methodology page.
For the full ranked list with scores and what sets each firm apart, go to the best home addition contractors in the GTA guide.
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All home additions & second storeys, ranked by score and relevance
We found 116 businesses offering home additions & second storeys; 63 met the criteria for the scored directory. The order weighs each business's overall score by how much of its reviewed work is home additions & second storeys, so a lower-scored specialist can rank above a higher-scored generalist. Filter and sort below, or open the full map view.
Enquiries from our contact forms may go to partner providers who can do the work, and we may receive a referral fee. Our rankings are based on our published scoring method only and are never affected by referral fees.
Common questions about home additions & second storeys
- How much does a home addition or second storey cost in the GTA?
- Ground-floor additions typically run in the range of $300 to $500 per square foot once you include finishes, permits, and engineering, though small bump-outs can come in lower and custom finishes push it higher. Second-storey additions tend to cost more per square foot than a ground-floor addition of the same size because the existing foundation and main floor structure usually need to be reinforced first. Get itemized quotes rather than a single lump sum so you can see what's actually driving the price.
- How long does a second-storey addition take?
- Design, engineering, and permitting alone can take two to four months in most GTA municipalities before any construction starts. Once permits are issued, construction on a second storey usually runs three to six months depending on size and how much of the existing roof and structure needs to be removed and rebuilt.
- Do I need a permit for a home addition?
- Yes. Any addition that changes the building's footprint or adds living space needs a building permit, and second storeys almost always require structural engineering review. If the addition doesn't meet current zoning setbacks or height limits, you may also need a minor variance approved through the local committee of adjustment before the permit can be issued.
- How do I judge the quality of a contractor's past work?
- Ask to see at least one completed project in person rather than just photos, and ask the homeowner directly about anything that went wrong after move-in, since every large addition has some post-construction issues (settling cracks, minor water intrusion at new roof-to-wall junctions). A contractor who talks openly about how they handled callbacks is usually more trustworthy than one who claims a perfect record.