My name is Nima. I’ve been in construction for over 20 years, working in home addition cost and new construction, renovations and project management. My first language is construction, not English or Persian.
This year, many homeowners ask me: “How much does it cost to add a room?” or “How much for a second floor on bungalow?” Here, I give you simple numbers and what I see daily on-site.
calculate home addition cost in 2025
In Toronto, the cost of home addition is $350 to $500 per square foot. If the job is more custom or complex, it can go even $600+.You can use these numbers in the preliminary design to adjust your budget correctly.
Some examples:
Rear Addition (approx. 400 sq.ft.)
Budget: $140,000 – $160,000
A straightforward ground-floor extension at the back of the house. Ideal for adding a family room, bedroom, or small office.
Kitchen Extension with Modern Upgrades
Budget: $200,000 – $250,000
Includes not just extra space, but upgraded finishes, structural work, plumbing, and electrical—one of the most complex additions.
Second Storey Addition on a Bungalow
Budget: $300,000 – $360,000+
This is a full structural transformation, essentially doubling the size of the home. Requires full engineering, roofing, and layout reconfiguration.
Always keep 10–20% extra for unexpected things. I never saw a job that came out 100% clean. Something always comes up, and this prevents many future problems between the homeowner and general contractors. Also, check the scope of work carefully.
Cost of home addition (400 SF Main Floor)
- Structure & Framing $25K – $35K
- Plumbing + Electrical $15K – $20K
- HVAC $5K – $8K
- Insulation + Drywall $8K – $12K
- Flooring, Trim, Paint $20K – $30K
- Permits + Drawings $5K – $10K
- Contingency $12K – $20K
- Total $140K – $170K
Price Depends Where You Build City / Area Cost per SF
- Toronto $350–$500
- Mississauga $250–$350
- Vaughan $270–$360
- Markham $280–$370
- Oakville $290–$380
- If you’re not in downtown Toronto, the cost is lower — fewer permit fees and easier access for trucks and trades. Parking and narrow alleys make the work harder.
What Affects the home addition cost?
• Size – A bigger job costs more in total, but sometimes less per sq. ft.(material cost is expensive these days )
• Design – A simple box is cheaper for home addition costs. Angled roof and steel beams = more money, and you have to be careful about the funds
• Permit / Zoning – You need permits. If you need a Committee of Adjustment, it costs more and adds delay. My suggestion is to get someone’s experience in construction, even at this stage
• Finishes – The price goes up fast if you want high-end tile, custom cabinets, and oversized windows.
• Site Access – If your house is a tight lot, has no rear access, or is old — it takes more time and labour.
How You Can Save Money by calculate home addition cost properly
- Don’t make a complicated design – a box shape is the fastest and cheapest to build
- Stack plumbing – Put new bathroom above old fixtures
- Buy your finishes – If you have time, buy your flooring or lights
- Use the same HVAC if possible – Save if the furnace or AC has enough capacity and check with experts
- Build in off-season – Some trades give better prices in winter as the construction is slow in this season
- Do phases – If the budget is tight, don’t finish the basement or deck right away
- Avoid steel beams – If structure allows, use LVL or wood to save
Common Questions I Hear about cost of home addition
Is it cheaper to go up or out?
Usually, up is cheaper. No new footings or digging in construction concrete, excavation and framing are significantly changing the home addition price.
How long it takes?
From 3–4 months for small jobs to 8–12 months for the second floor. Make sure that for your home extension, you always get the project timeline or even a Gantt chart to check each step and help your general contractor as a team member.
Do I need permits?
Yes. It’s always in Toronto. Some jobs also need zoning change or variance. Starting this much construction work without a permit can cause many problems for you later, like when you are selling your property, home insurance, worker safety and health, and neighbours complain.
Final Words
A good home addition will give you more space, comfort, and value. But you need to plan it right. I tell all my clients to keep the design simple, stay involved, and work with someone who understands city rules.
At Renotec, we don’t sell dreams. We build homes and provide quality home improvement. If you’re in Toronto or GTA and thinking of adding space to your house, I can help you understand what’s possible — no pressure and always get quotes from three general contractors.