Dormer Addition Cost Toronto 2026: Shed, Gable, Eyebrow Pricing

# Dormer Addition Cost Toronto 2026: Shed, Gable, Eyebrow Pricing

A dormer addition is the structural intervention that turns a 1.5-storey Toronto home from "tight attic with sloped ceilings" into a full habitable floor with standing headroom. The cost of that intervention varies almost three-fold depending on which dormer type you choose: a simple rear shed dormer runs $15,000 to $30,000, a traditional gable dormer runs $20,000 to $40,000, and an architectural eyebrow dormer runs $30,000 to $60,000.

These are dormer-only numbers — the structural shell of the dormer itself, including the engineered beam, framing, sheathing, roofing, and exterior cladding. They do not include the interior finishes, insulation, electrical, plumbing, or stair work that turn the attic into a livable room. For full project costs covering all of that, see [Attic Conversion Cost Toronto: Full Comparison](/blog/attic-conversion-cost-toronto-comparison). For the broader pillar context, see [Attic Conversion Toronto 2026: Complete Guide](/blog/attic-conversion-toronto-2026-complete-guide).

This post breaks down what's actually in those numbers, why each dormer type costs what it does, and the Toronto-specific variables (Heritage Permit, P.Eng, neighbourhood) that move you within or outside the range.

What's Inside a "Dormer Cost" Number

Before comparing dormer types, here's what a complete dormer scope includes:

• Structural design and P.Eng stamp. Drawings, calculations, and a sealed engineering letter for the new ridge beam and any reinforcement of existing rafters. Typical cost in 2026 Toronto: $1,800 to $3,500 for a single dormer.
• Permit drawings. Architectural drawings for Toronto Building. $1,500 to $3,500 depending on complexity.
• Building Permit fees. Toronto Building charges roughly $19 per $1,000 of construction value, plus a flat application fee. A $25,000 dormer permit costs around $700 to $900 in fees.
• Heritage Permit (if applicable). No additional fee for the Heritage Permit itself, but adds 6 to 12 weeks to timeline and may require a heritage consultant ($2,000 to $5,000) for HCD properties.
• Demolition. Cut roof opening, remove existing finishes, dispose of debris. $1,500 to $3,500.
• Structural beam. LVL or steel beam carrying the existing roof load above the dormer cut. Material plus install: $2,500 to $6,500 depending on span and whether crane access is needed.
• Framing. Dormer walls, dormer roof, headers, sister rafters where required. $4,000 to $12,000 depending on dormer size and roof type.
• Sheathing and weather barrier. Plywood or OSB plus housewrap. $1,200 to $3,000.
• Roofing. Asphalt shingles or membrane on the new dormer roof, integrated with existing main roof. $2,500 to $6,000.
• Exterior cladding. Siding, brick veneer, or stucco to match the existing home. $3,000 to $10,000 depending on material.
• Windows. One or more dormer windows, including egress-rated where required. $1,500 to $5,000.
• Flashings and integration. Step flashing, valley flashing, and tie-in to existing roof. $800 to $2,000.

Shed Dormer: $15,000 to $30,000

A shed dormer has a single flat or low-slope roof that runs across the back of the house. Structurally, it's the simplest dormer to build because there's only one roof plane, two short side walls, and one long front wall. The new ridge beam runs horizontally along the top of the new front wall, and the existing roof rafters are cut and tied into a header at the dormer cut.

What Drives the $15K end of the range

• Rear-only location (no Heritage Permit required even in HCDs because not visible from street)
• Width of 4 to 6 m
• Asphalt shingle roof matching existing
• Vinyl or aluminum siding matching existing
• LVL beam (cheaper than steel, fits typical 4 to 6 m span)
• Standard egress window, no skylight
• No crane required (beam can be man-handled into place)

What Pushes Cost to $30K

• Width of 8 to 10 m (longer beam, more framing)
• Steel beam required for spans above 7 m
• Brick or stone veneer cladding to match existing
• Premium windows (triple-pane, casement, large)
• Crane required for beam placement
• Complex roof tie-in (existing valleys, hips, or chimney in the way)

Best For

Master suite conversions where usable interior floor area is the priority. A shed dormer adds 60 to 100 sqft of full-headroom floor area for every linear metre of width — the highest space-per-dollar ratio of any dormer type. For most Beaches, Mimico, East York, and Junction homes, a single rear shed dormer is the right answer.

Gable Dormer: $20,000 to $40,000

A gable dormer has a peaked roof matching the slope of the main house roof. Structurally, it's more complex than a shed dormer because the dormer roof has two slopes meeting at a ridge, plus two valley conditions where the dormer roof meets the main roof. The framing involves jack rafters, valley rafters, and a small ridge beam, all of which add labour hours.

What Drives the $20K End of the Range

• Single small gable dormer, 2 to 3 m wide
• Rear or side location (no Heritage Permit)
• Asphalt shingles matching existing
• Vinyl or aluminum siding matching existing
• Standard double-hung window

What Pushes Cost to $40K

• Two or three gable dormers across a front roof (multiple structural cuts, multiple valleys, multiple permit drawings)
• Front-facing in a Heritage Conservation District (Heritage Permit, heritage consultant, possible custom millwork to match historic detailing)
• Wider gable (4 to 5 m, requiring full ridge beam)
• Custom window proportions to match historic neighbours
• Brick veneer matching existing
• Decorative trim, brackets, or fascia detailing

Best For

Front-facing dormers in HCDs, traditional Edwardian and Victorian homes where the dormer must read as part of the original architecture, and homes where the owner specifically wants a peaked-roof aesthetic over the maximum-space shed approach. Two or three gable dormers across a front roof can add the same total floor area as one shed dormer, but at 1.5 to 2 times the cost.

Eyebrow Dormer: $30,000 to $60,000

An eyebrow dormer has a curved roof that arcs out of the main roof slope without a vertical front wall — the roof bends to form a low arch over a wide window. Structurally, it's the most complex dormer type because the curved framing requires custom-cut rafters or laminated curved members, and the roofing requires either custom curved metal or specially-bent shingle work.

What Drives the $30K End of the Range

• Small eyebrow, 2 to 3 m wide
• Rear or side location (no Heritage Permit)
• Standard asphalt shingles bent to the curve (limited curve radius)
• Single arched window

What Pushes Cost to $60K

• Wide eyebrow (4 to 5 m) with tighter curve radius
• Custom laminated curved beam
• Standing-seam metal roofing (the only material that handles tight eyebrow curves cleanly)
• Custom curved window with insulated glazing
• Front-facing in a Heritage Conservation District
• Heritage consultant required for HCD review of curved-roof addition

Best For

Heritage homes where a flat-faced shed or peaked gable would clash with the existing architecture, premium custom builds where the eyebrow becomes a signature design feature, and homeowners who prioritize curb appeal over interior floor area. Eyebrow dormers add the least usable floor area per dollar — typically 30 to 50 sqft per eyebrow at $30K to $60K — so they're an aesthetic choice, not a space-maximization choice.

Cost Multipliers Specific to Toronto

Three Toronto-specific factors move dormer costs within and beyond the ranges above:

Heritage Conservation District Surcharge

If your home is in Cabbagetown North, Cabbagetown South, Old Riverdale, Wychwood Park, Casa Loma, or another HCD, expect:

• 6 to 12 weeks added to permit timeline (Heritage Preservation Services review before Building Permit)
• $2,000 to $5,000 for a heritage consultant to prepare the Heritage Impact Assessment
• Possible scope changes (gable instead of shed, smaller dimensions, specific window proportions)
• Higher-cost materials (matching brick, custom millwork, slate or metal roofing where original)

Net HCD impact: typically $5,000 to $15,000 added to the dormer cost, more for street-facing alterations. See [Dormer Heritage Permit Toronto: HCD Restrictions](/blog/dormer-heritage-permit-toronto-hcd) for full HCD guidance.

P.Eng Beam Span and Material

Spans up to 4 m can usually be carried by a 9-1/2" LVL ($800 to $1,500 in materials). Spans of 4 to 6 m typically need a 14" LVL or doubled LVL ($1,800 to $3,500). Spans above 6 m almost always require a steel W-beam ($3,500 to $6,500 with crane install). The P.Eng's beam selection is one of the largest single-line variables in the dormer cost.

Roof Tie-In Complexity

Simple tie-in (clean main roof slope, no valleys or chimneys near the dormer cut): no surcharge. Complex tie-in (existing valley, hip, or chimney within 1 m of the dormer): expect $2,000 to $5,000 in additional flashing and framing labour. Have your contractor walk the roof before quoting.

Dormer Cost vs Total Conversion Cost

Remember: the dormer is only the structural shell. A complete attic conversion includes the dormer plus interior finishes, insulation, electrical, plumbing, stair, and ensuite. The relationship looks like this:

• Shed dormer ($20K) + interior conversion to master suite ($110K) = $130K total project
• Two gable dormers ($55K) + interior conversion ($130K) = $185K total project
• Eyebrow dormer ($45K) + interior conversion ($120K) = $165K total project

For full project budgeting, see [Attic Conversion Cost Toronto: Full Comparison](/blog/attic-conversion-cost-toronto-comparison).

How to Get Honest Dormer Pricing

Three things to ask any contractor quoting your dormer:

• 1. Show me the P.Eng beam line item. If they don't have a specific dollar amount for engineering and the beam material, they're not pricing the structure honestly.
• 2. What is your span assumption? Beam material and cost scale strongly with span. A contractor who quotes a flat number without measuring your roof can be off by $3,000 to $6,000.
• 3. Are you including Heritage Permit time? If the property is in an HCD and the dormer is street-facing, the timeline is the cost. A contractor who promises a 4-week start in an HCD is either wrong or planning to skip the permit.

Next Steps

If you're sizing budget for a Toronto dormer addition, the right next step is a structural feasibility visit: roof measurements, span assessment, photograph documentation, and a written letter naming the dormer type and budget tier that fits your home.

[Request a dormer feasibility visit](/services/home-renovation/attic-conversion-dormer) — RenoHouse handles design, P.Eng, Heritage review where needed, and full build.

For the full conversion framework, return to the pillar: [Attic Conversion Toronto 2026: Complete Guide](/blog/attic-conversion-toronto-2026-complete-guide). For dormer-type comparison, see [Shed vs Gable vs Eyebrow Dormer: Toronto Comparison](/blog/shed-vs-gable-vs-eyebrow-dormer-toronto).