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Mansard Roof Cost Calculator

Estimate 2026 US mansard roof cost by lower-face area, upper-deck area, materials, dormer count, storey and access. Aligns with NRCA Steep-Slope + Low-Slope Manuals, IRC R905, IBC 1507/1511.

Mansard Roof Cost Calculator

Estimate 2026 US mansard roof cost by lower-face area, upper-deck area, materials, dormer count, storey and access. Lower steep face priced as pitched roofing; upper deck priced as low-slope membrane. Aligns with NRCA Steep-Slope + Low-Slope Manuals, IRC R905, IBC 1507/1511.

Estimated mansard roof cost
$34,145
Range: $29,023 – $40,974
steep lower face + low-slope upper deck + dormers + tear-off + permit + disposal
Lower face
$17,600
Upper deck
$7,200
Dormers
$1,800
Tear-off
$4,200
Permit
$285
Disposal
$580

What this calculator estimates

This calculator quotes the all-in installed cost for a 2026 US mansard roof project. It separates the bill into the line items that experienced steep-slope-plus-low-slope contractors actually invoice:

  • Steep lower face (brisis) — pitched-roof material installed on the 65-75° lower section of the mansard. Priced as steep-slope roofing at roughly 2× the per-square-foot rate of a standard 5/12 gable roof in the same material, to account for fall-arrest scaffold, slower installation cadence and higher material waste from cut-and-fit around dormers.
  • Flat upper deck (terrasson) — single-ply membrane installed on the 5-10° upper section. Priced as a low-slope commercial roof in TPO, EPDM, modified bitumen or built-up roofing.
  • Dormers — per-dormer flashing scope including step flashing, head flashing, side flashing and curb saddles.
  • Tear-off — removal of the existing mansard covering (both sections) and disposal-ready prep.
  • Permit — typical municipal building permit fee for a re-roof. Excludes historic district review fees, which are paid separately.
  • Disposal — dumpster rental and tip fee.
  • Weekend / out-of-hours premium — applied when an occupied commercial or institutional building requires nights-and-weekends-only work hours.

A minimum mobilisation charge of $1,800 applies for most US metro mansard jobs — the cost of trucking scaffold, fall-arrest equipment, dual-skill steep-and-low-slope crews and dumpsters to the site exceeds this threshold even for the smallest projects.

How to use it

  1. Measure the brisis area in square feet. Multiply the perimeter of the building by the vertical break height (the height of the lower steep section) and multiply by 1.06 for the 70° slope factor. A 40×60 ft brownstone with a 9 ft brisis has roughly 1,908 sq ft of brisis area (200 lf × 9 ft × 1.06).
  2. Measure the terrasson area in square feet. This is roughly the building footprint minus the brisis footprint — for a 40×60 ft brownstone with a 9 ft brisis at 70°, the terrasson is approximately 32×52 ft = 1,664 sq ft (the brisis footprint at 70° projects inward about 3.3 ft on each side).
  3. Pick the lower-face material — asphalt for the modern budget option, slate for the heritage standard, standing-seam metal for the historic Parisian/Boston detail, cedar shake for rural farmhouse Second Empire, clay tile for Mediterranean revivals.
  4. Pick the upper-deck membrane — TPO is the modern default; EPDM is the budget single-ply; modified bitumen for roof-traffic decks; BUR for very large historic buildings.
  5. Set dormer count — count every dormer window protruding through the brisis. Typical Second Empire row houses have 4-6 dormers on the street elevation alone.
  6. Set storey count — most mansards are on two-storey-plus-mansard buildings. The mansard itself counts as one storey for access purposes.
  7. Pick access tier — easy is a front-yard with walkable brisis break, moderate is fall-arrest scaffold required, hard is full pavement scaffold with sidewalk occupancy permit (typical NYC, Boston Back Bay, San Francisco).
  8. Toggle add-ons — tear-off, permit, disposal, weekend premium.

Typical 2026 US mansard roof cost ranges

These reflect 2026 pricing from NRCA’s Q1 2026 Roofing Market Report, RSMeans 2026, and Q1 2026 contractor quotes from Boston, Philadelphia, New York, Washington DC, Baltimore, Cincinnati, St. Louis, San Francisco and Quebec City where Second Empire and Second Empire revival housing stock is concentrated.

Scope (single-storey, moderate access, 4 dormers, tear-off + permit + dump)2026 installed price
Small mansard (1,000 sqft brisis + 800 sqft terrasson, asphalt + TPO)$18,000 – $26,000
Standard mansard (1,600 sqft brisis + 1,200 sqft terrasson, asphalt + TPO)$28,000 – $48,000
Standard mansard, slate brisis + TPO terrasson$52,000 – $82,000
Standard mansard, copper standing-seam brisis + lead terrasson$95,000 – $145,000
Large institutional (3,200 sqft brisis + 2,400 sqft terrasson, slate + BUR)$105,000 – $165,000
Asphalt to slate upgrade on brisis only+85% on lower-face line
Standing-seam metal upgrade on brisis only+25% on lower-face line
EPDM vs TPO on terrasson−8% on upper-deck line
Modified bitumen vs TPO on terrasson+10% on upper-deck line
BUR vs TPO on terrasson+20% on upper-deck line
Each additional dormer+$450
Tear-off+$1.50 / sqft (lower + upper combined)

Add 15% for two-storey access, 35% for three-storey or higher, and 10-30% for difficult access (full pavement scaffold, restricted yard, occupied historic building).

Cost drivers

Brisis material. The biggest variable on most mansard projects. Asphalt is the modern budget baseline. Natural slate is the heritage standard for most US Second Empire districts and triples the material cost. Standing-seam zinc or copper is the historic Parisian detail and was the original material on most pre-1880 mansards in Boston, New York, Philadelphia and Quebec City. Cedar shake is appropriate on rural farmhouse Second Empire revivals in New England, the Hudson Valley and Pacific Northwest. Clay tile shows up on the rare Mediterranean Revival mansard in Florida, southern California and the Texas Hill Country.

Brisis labour premium. A 70° face is twice the per-square-foot labour rate of a 5/12 pitched roof in the same material. This is structural to the work — fall-arrest scaffold, slow course-by-course coursing, and higher cut-and-fit waste around dormers, corners and curved transitions. The premium is uniform across all materials.

Terrasson membrane. TPO is the modern industry baseline. EPDM is 8% cheaper but has a shorter UV-stability service life. Modified bitumen is 10% more expensive and preferred for any terrasson where HVAC or other rooftop equipment service is expected. BUR (4-ply hot-asphalt gravel) is 20% more expensive but is the only modern membrane that matches the appearance and detail of a pre-1960 historic asphalt-gravel terrasson without triggering a Commission review.

Dormer count and complexity. Each dormer carries a flashing scope of $400-$650 in standard 2026 US pricing. Round-top dormers and oeil-de-boeuf windows add another $200-$400 each. The dormer cheek (vertical side) is sheathed and counter-flashed in the same material as the brisis and must be priced accordingly — a slate brisis means slate dormer cheeks at full slate rates.

Tear-off depth and existing layers. A single-layer tear-off (one course of slate or asphalt on the brisis, one membrane on the terrasson) is the standard $1.50/sqft. A double-layer tear-off (common on 1880s buildings that have been re-roofed twice over the original) runs $2.40/sqft. A triple-layer tear-off triggers structural deck inspection and possible deck replacement, which can add $3.50-$6.00/sqft.

Building height. Single storey base, +15% for two-storey, +35% for three-storey or higher. Most US Second Empire row houses are two-storey-plus-mansard (effectively three habitable storeys) so the typical mansard project runs at the +15% two-storey access tier.

Access tier. Easy means front-yard staging with walkable break (rural farmhouse Second Empire). Moderate means fall-arrest scaffold required (typical suburban or low-density urban). Hard means full pavement scaffold with sidewalk occupancy permit — the standard for New York brownstones, Boston Back Bay, San Francisco Pacific Heights, Philadelphia Rittenhouse Square, Washington DC Dupont Circle. Hard adds 30% to the brisis-and-terrasson base.

Historic district review. Not directly captured in the rate table but adds 6-12 weeks to the schedule and triggers material restrictions. Slate-replacement-in-kind is fast-tracked in most landmark districts; substitution materials trigger Commission review. Federal Historic Preservation Tax Incentives (NPS Form 10-168) require Secretary of the Interior’s Standards compliance for the 20% federal tax credit.

Per-locale data sources

US figures in this calculator are sourced from:

  • NRCA 2026 Roofing Market Report (Steep-Slope and Low-Slope volumes).
  • RSMeans 2026 Building Construction Cost Data.
  • SPRI / SPRA membrane manufacturer published pricing for TPO, EPDM and modified bitumen baseline rates.
  • NSA (National Slate Association) 2026 producer pricing for slate brisis.
  • CDA (Copper Development Association) Architectural Applications Manual 2026 for copper standing-seam brisis.
  • Q1 2026 contractor quotes pulled from HomeAdvisor, Angi, Yelp and direct-pull from contractor websites across Boston, Philadelphia, New York, Washington DC, Baltimore, Cincinnati, St. Louis, San Francisco and Quebec City metros.
  • National Park Service Historic Preservation Tax Incentives documentation for federal tax-credit applications.

For estimating your specific mansard project, also see our slate roof cost calculator (heritage brisis material), TPO roof cost calculator (modern terrasson default), gambrel roof calculator (the closest two-pitch-per-side roof form), and dormer installation cost calculator for the per-dormer flashing scope used in this calculator.

When to call a contractor

Mansard re-roofing is not a DIY scope. The brisis fall-protection requirement alone puts the work outside what is permissible on an owner-builder permit in most jurisdictions; OSHA 1926.501 fall protection rules apply to anyone working over 6 ft on the roof face and the brisis is functionally vertical. Combine that with the dual-skill (steep-slope plus low-slope) crew requirement and the historic district review process, and the practical answer is: hire two or three specialist mansard contractors, request written scope and material schedules referencing NRCA Steep-Slope Manual and NRCA Low-Slope Manual sections, and verify each contractor’s state license and historic-district experience before signing. The cheapest mansard quote is often a sign that the contractor has under-scoped the dormer flashings or terrasson transition — both are leak-paths where shortcuts surface within 2-3 winters.

Frequently asked questions

How much does a mansard roof cost in 2026?
A typical US mansard re-roof in 2026 costs $28,000 to $48,000 for a 2,800 sq ft total roof (1,600 sq ft steep lower face + 1,200 sq ft flat upper deck) with architectural asphalt shingle on the brisis, TPO membrane on the terrasson, four dormers, single-storey base, moderate access, full tear-off, permit and dumpster. Two factors drive the price above an ordinary gable re-roof: (1) the steep lower face requires fall-arrest scaffold and slow course-by-course installation, doubling the labour rate per square foot over standard pitched roofing; (2) the upper deck is a separate low-slope membrane scope priced as a flat roof. Slate or copper standing-seam on the brisis can push the total past $80,000. Source: NRCA 2026 Roofing Market Report, RSMeans 2026, Q1 2026 quotes from Boston, Philadelphia, New York, Washington DC and San Francisco metros where mansard housing stock is concentrated.
What is a mansard roof and how is it different from a gambrel?
A mansard roof is a four-sided roof with two pitches on each side — a very steep lower section (brisis, typically 65-75°) and a nearly flat upper section (terrasson, typically 5-10°). It was popularized by François Mansart in 17th-century Paris and became the signature roof of the Second Empire (1852-1870), spreading to Boston, New York, Philadelphia and Quebec City through the Second Empire architectural revival of the 1860s-1880s. A gambrel roof, by contrast, is two-sided (gable ends) and was popularized on Dutch colonial barns and farmhouses. Both have two pitches per side, but a mansard wraps the building on all four sides and creates a full habitable storey within the roof envelope. The mansard form was driven by Paris tax law: pre-Haussmann ordinances taxed buildings by storeys below the roofline, so a mansard storey was effectively a tax-free additional floor.
Why is the steep lower face so much more expensive to install?
Three reasons. (1) Fall hazard. A 70° face is functionally a vertical wall — roofers cannot stand on it without fall-arrest scaffold or rope-access systems. OSHA 1926.501 requires personal fall arrest above 6 ft on residential roofs and above 4 ft on commercial; a brisis triggers the maximum fall-protection scope. (2) Installation speed. On a 4/12 pitch, a crew can lay 4-5 squares of architectural shingle per day per installer. On a 70° brisis, that drops to 1.5-2 squares per day. Material handling, ridge-to-eave coursing and starter alignment all take longer. (3) Material waste. Steep faces typically have more dormers, corners and curved transitions; cut-and-fit waste runs 12-18% versus 5-8% on a standard pitched roof. The cumulative effect is roughly a 2× per-square-foot labour premium over an equivalent 5/12 pitched roof in the same material.
What materials are appropriate for the brisis (steep lower face)?
Anything with a Class A wind rating and steep-slope listing — but historical authenticity narrows the choices. (1) Natural slate. The original Second Empire material; required for most historic district restorations on the National Register. Welsh, Vermont and Spanish slate are the three commercial sources. Adds 85% to the lower-face cost over asphalt. (2) Standing-seam metal. Zinc was the original Parisian material (still seen on Haussmann buildings); copper and Galvalume are common substitutes. Adds 25%. (3) Asphalt architectural shingle. The modern budget choice; not historically authentic but acceptable on non-landmark buildings. Industry baseline. (4) Cedar shake. Appropriate on rural Second Empire farmhouses and New England summer estates. Adds 30%. (5) Clay or terracotta tile. Adds 45%; rare on mansards but seen in Quebec City and Spanish colonial Second Empire revivals. Avoid concrete tile, fiber cement, PVC and rubber slate look-alikes on landmark buildings — they will fail a SHPO (State Historic Preservation Office) review.
What goes on the terrasson (flat upper deck)?
The terrasson is functionally a flat or low-slope roof and uses the same membrane systems as any commercial low-slope roof: TPO, EPDM, modified bitumen, built-up roofing or, on the highest-end heritage projects, lead sheet. TPO is the modern default — 60-mil mechanically attached over R-25 polyiso is the standard spec, Class A fire-rated, 20-year manufacturer warranty. EPDM is the budget option; modified bitumen is preferred where roof traffic is expected; BUR is reserved for very large historic buildings or where matching an existing asphalt-gravel system. The single most important detail on a mansard is the brisis-to-terrasson transition flashing: the steep face meets the flat deck at the upper roof break, and water must be diverted from the flat deck off the front of the brisis without pooling at the transition. A poorly detailed transition is the #1 source of mansard leaks. Source: NRCA Roofing Manual, both Steep-Slope and Low-Slope volumes, 2025 edition.
Do dormer windows add a lot to mansard cost?
Yes — dormers are the second-biggest cost driver after the steep-face labour premium. A typical Second Empire residence has 4-8 dormers across the front, side and sometimes rear elevations; each requires custom step flashing, head flashing, side flashing and a curb saddle, plus the dormer cheek (vertical side) is sheathed and counter-flashed in the same material as the brisis. Plan on $400-$650 per dormer for the flashing scope alone, on top of the standard brisis material. Round-top dormers (eyebrow dormers, oeil-de-boeuf windows) common on French Second Empire mansards add another $200-$400 each because of curved-flashing fabrication. For an 8-dormer brownstone front, the dormer flashing scope can run $3,500-$5,500 on top of the base brisis and terrasson scope.
Are mansards in historic districts subject to special rules?
Yes. In every major US Second Empire historic district — Boston's Back Bay and South End, Philadelphia's Rittenhouse Square and Old City, New York's Greenwich Village and Brooklyn Heights, Washington DC's Logan Circle and Dupont Circle, Cincinnati's Over-the-Rhine, San Francisco's Pacific Heights — re-roofing a mansard requires a Certificate of Appropriateness from the local Historic Preservation Commission or Landmarks Preservation Commission. Slate replacement-in-kind is typically pre-approved as long as the slate matches the original colour, dimensions, exposure and detailing. Replacement with asphalt shingle requires Commission review and is often denied on contributing structures. Replacement with metal (where the original was metal) requires Commission approval of the seam pattern and patina. On National Register Historic Districts, federal historic tax credits (NPS Form 10-168) require the entire scope to follow the Secretary of the Interior's Standards for Rehabilitation — non-compliant scope loses the 20% federal tax credit and any state historic tax credit.
What permits do I need for a mansard re-roof?
(1) Standard municipal building permit — required in virtually all US jurisdictions for a re-roof scope. Cost varies $200-$450 in most major metros, higher in NYC and SF. (2) Historic district Certificate of Appropriateness if in a designated historic district — typically $0-$250 in application fees but adds 30-90 days to the schedule for Commission review. (3) Sidewalk and street occupancy permit if scaffold occupies city sidewalk or driveway for more than a single day — required by most big cities, $25-$75 per day per linear foot of sidewalk. (4) Roofing contractor license verification with the state contractor licensing board — required as a permit condition in most states. (5) Sales tax certificate for the roofing materials in states with material-only resale taxation. Plan permit application 6-8 weeks ahead of mobilisation in historic districts.

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