How Much Does a Home Addition Cost in Toronto?

The two builders define their prices differently. Lighthaus states that its figures cover materials and labour only. Allard lists what its bungalow price includes and prices changes to the floor below separately. Compare a quote with the row whose scope matches it.

What does the cost per square foot include?

A published rate is only useful if you know which area and which work it covers.

New space and changes to your existing house

Four distinctions matter:

• New floor area. Lighthaus applies its rates to the size of the addition itself, for example $450 to $550 per square foot on a 500 sq ft rear addition.
• Existing rooms that also change. Opening the back wall, moving a kitchen or rebuilding a main floor is extra work on space you already have. Allard excludes main-floor renovations from its second-storey price and quotes them separately: as little as $25,000 to $35,000 for lighter kitchen work, and $100,000 to $125,000 to gut the floor with a new kitchen and powder room (Allard, 2025 (opens in a new tab)).
• Construction versus the whole budget. Hard costs are materials and labour. Design, engineering, permits, HST and temporary housing sit outside Lighthaus’s rates.
• Footprint versus total floor area. A two-storey rear addition adds floor on two levels over one foundation. Ask whether a rate is per square foot of footprint or of total new floor area, and whether a basement is counted.

Do not apply a rear-addition rate to a second storey, or a new-construction rate to renovated rooms. The City measures areas differently too: new floor area to the outer face of exterior walls, and renovations by the total area affected (City permit fees (opens in a new tab)).

Rear addition costs in Toronto

A rear addition extends the main floor, usually for a larger kitchen, dining area or family room. Lighthaus describes 400 to 600 sq ft as the most common scope for Toronto houses.

What changes a rear addition’s price:

• What is underneath. A full basement below the addition adds excavation and foundation work (Lighthaus (opens in a new tab)).
• The connection to the house. Additions are typically built and partly finished before the connecting wall is removed (CHBA (opens in a new tab)). The size of that opening, and any beams it needs, belong in the quote.
• Kitchens and bathrooms. They carry plumbing, ventilation and cabinetry that a family room does not.
• Zoning limits. Setbacks and lot coverage decide how far back you can build. A design outside them needs a minor variance (City (opens in a new tab)).
• Access. Narrow side yards and rear-lane access affect how materials arrive and soil leaves.

Two-storey rear additions add floor on both levels. We found no builder that prices them as their own scope, so ask for the rate per square foot of total new floor area and for the stair, roof and second-floor connection to be itemized. Kildrin’s Toronto addition permit data shows historical construction values declared at filing for permits that mention a rear or two-storey addition. It has no floor areas, so it cannot give a rate per square foot.

Second storey addition costs in Toronto

A second storey, or bungalow top-up, adds a new floor over an existing one-storey house or rear extension. Lighthaus’s range for it runs higher than its rear-addition range. The reasons are in the structure and systems:

• Can the house carry it? Adding a storey changes how loads travel through the house, and existing foundations may need reinforcement or underpinning (Sepco Consulting Engineers (opens in a new tab)). Not every house can take a second floor without that work, so an engineer’s assessment comes first.
• The roof comes off. The existing roof is removed and a new one built, which is a significant labour cost and exposes the house to weather (Lighthaus (opens in a new tab)).
• Stairs. A new staircase takes space on the main floor and often changes its layout.
• Heating, plumbing and electrical. On a bungalow they were not designed for another floor. Allard notes that permit drawings must include a new heat-loss calculation for the heating system (Allard (opens in a new tab)).
• Living elsewhere. Lighthaus says many families move out for five to seven months and cites $4,000 to $10,000 a month for Toronto rent.

Allard’s price shows how scope shifts the total: from about $300,000 for an 800 sq ft second storey with most of the main floor left as is, and from about $450,000 for a 1,200 sq ft three-bedroom top-up that includes a main-floor gut (pricing as of September 1, 2025 (opens in a new tab)).

Small extensions and room additions

We found no Toronto builder figure for a bump-out or single-room addition with a defined scope, so this guide gives no rate. A small addition still needs a foundation, a roof tied into the house, an opening into the existing room, permit drawings and City fees. Ask for those items to be listed separately, because on a small project they make up a larger share of the total.

What extra costs should you check before setting a budget?

Each figure as published by its source. They cover different scopes and should not be added together as a project total.

Is a second storey cheaper than a rear addition?

Not necessarily. Lighthaus publishes the same starting rate for both, $450 per square foot, and a higher upper rate for a second storey: $650, against $550 for a rear addition. It links the extra cost to the roof coming off, structural reinforcement, a new staircase and extended systems. Overlapping ranges do not show that either type is always cheaper.

What decides the comparison for your house is how much floor area you need, how much structural work the existing house needs and how much of it changes. Lighthaus notes that a second storey adds the most living space for its footprint and leaves the yard untouched.

Which is better for your house depends on:

• How much space you need. Compare the cost of the floor area you actually need, not totals for different sizes.
• Your lot. Rear setbacks and lot coverage may stop a rear addition; height limits may stop a second storey.
• The existing structure. A second storey depends on what the foundation and walls can carry.
• The main floor. A new stair and system changes affect the rooms below a second storey; a rear addition mainly affects the back wall and kitchen.

Permits, approvals and timing

• Permit. Additions, including second and third storeys, need a building permit (City (opens in a new tab)). The City has a Small Residential Additions guide (opens in a new tab) listing the required drawings.
• Zoning review first. A complete House-stream application needs an issued Zoning Applicable Law Certificate (City (opens in a new tab)). The certificate costs $644.38 for additions to houses and includes up to three reviews (City, 2026 (opens in a new tab)).
• Minor variance, only if needed. If the design does not meet zoning limits such as setbacks, you apply to the Committee of Adjustment. The 2026 fee for additions to dwellings with three units or less is $2,228.98 (City (opens in a new tab)). Neighbours within 60 metres are notified at least 10 days before the hearing (City (opens in a new tab)). The City does not publish a typical total time for the process.
• Building permit fee. The fee is the service index times the floor area of the work: $18.56 per square metre for single-family dwellings, semis and townhouses, with a $214.79 minimum (City, 2026 (opens in a new tab)). A heating, ventilation and air conditioning permit ($270.64 flat for a house) and plumbing ($23.20 per fixture) are charged separately. These are City fees, not the cost of approvals.
• Review time. The City reviews complete House-stream applications within 10 business days (City (opens in a new tab)). Additions are not eligible for the faster Express Services stream (City (opens in a new tab)), despite some builder pages suggesting a fast track. Design, zoning review and any variance come before the permit review, and construction time is separate again.

Preparing to request a quote

Before contacting builders, note:

• The addition type: rear, two-storey rear or second storey.
• Its approximate size and the rooms you want in it.
• Any existing drawings or a property survey.
• What changes in the current house: kitchen, stairs, back wall or main floor.
• The finish level you expect, and anything you will handle yourself.

Then ask each builder to state what is included, what is an allowance and what is excluded. The quote comparison guide covers allowances, taxes, payment milestones and changes.