The mansard roof looks incredible on paper—extra attic space, classic French architecture, that Tudor cottage vibe everyone loves. Then you get the replacement quote and nearly pass out. I’ve walked homeowners through this exact scenario dozens of times. That beautiful double-mansard roof sloped roof you fell in love with? It’s about to become your most expensive home maintenance project.
Let me break down what a mansard roof actually is and what you’re signing up for.
What Is a Mansard Roof? (The Real Mansard Roof Definition)
A mansard roof is a four-sided roof with two distinct slopes on each side.
The lower slope is almost vertical—seriously steep, usually 70-80 degrees. The upper slope sits at a gentler angle, around 35 degrees, and you often can’t even see it from street level.
Think of it as your home’s outer walls being roof instead of siding. That’s the simplest way to visualize mansard roof design.
Also called a French roof or curb roof, this style originated in 16th-century France when architect Pierre Lescot used it on the Louvre in 1546.
But it got named after François Mansart, who slapped it on practically every building he designed in the 17th century. His great-nephew Jules Hardouin-Mansart made it mainstream at the Palace of Versailles.
What Does a Mansard Roof Look Like?
Look at any mansard roof images online and you’ll spot the pattern immediately.
The most obvious feature is that steep, almost-vertical lower section wrapping around all four sides of the building. No flat gable edges—just continuous roofing on every side.
The upper section has a much gentler slope leading to the ridge. Often completely invisible from the ground.
Types of mansard roof styles:
Straight mansard: Basic design with an almost vertical lower slope in a straight line.
Convex mansard: Lower slope curves outward like a bell.
Concave mansard: Lower slope curves inward.
S-shape mansard: Mix of convex and concave, creating an S-curve from top to bottom.
Most modern mansard roof houses use the straight style because it’s simpler to build and maintain.
The Purpose of a Mansard Roof (Why Anyone Would Want This)
What is the purpose of a mansard roof? Extra livable space without building outward.
That steep lower slope creates usable attic space instead of wasted triangular voids like you get with hip or gable roofs.
In 18th-century France, some cities had height restrictions that measured up to the ridge. Clever architects used mansard roofs to squeeze in an extra floor while technically staying under the limit. They also avoided municipal taxes based on the number of floors. Smart.
The mansard roof extension became popular in urban areas where space costs a premium. You’re essentially adding a room without expanding your home’s footprint.
Dormers punched through that steep lower section bring in natural light. The whole attic becomes a functional living space.
Mansard Roof vs Gambrel Roof (Not the Same Thing)
What is the difference between a gambrel and mansard roof? Four sides versus two. A gambrel roof has the same double-slope profile but only on two sides. The other two sides are flat gable edges.
Think of a classic barn—that’s a gambrel roof. A mansard roof wraps that double-slope design around all four sides. No gable edges anywhere. Both create extra attic space, but the mansard gives you more because it surrounds the entire top floor.
Materials for Mansard Roof Construction (This Gets Expensive)
What is the best material for a mansard roof? Definitely not standard asphalt shingles.
That near-vertical lower slope means asphalt shingles can slide off if not installed perfectly. The weight also becomes a problem.
Better options:
Synthetic slate or cedar shake shingles: Lightweight, premium materials that mimic traditional looks without the weight. More expensive than asphalt but won’t slide off.
Natural slate: Traditional choice, looks incredible, lasts forever. Extremely expensive and requires specialized installers.
Wood shake or tile: Classic materials used on historical mansard roof houses. Beautiful but pricey and maintenance-intensive.
Metal mansard roof: Growing in popularity. Lightweight, durable, and handles the steep pitch well. A mansard brown metal roof or darker colors hide imperfections better than lighter options.
The upper low-slope section (anything below 2:12 pitch) needs a water-tight membrane like EPDM, TPO, or PVC to handle sitting water.
You can’t see this part from the street, so pick based on functionality. TPO and PVC are white and reflective, keeping rooms cooler. EPDM is black rubber that’s nearly bulletproof.
Why Mansard Roof Replacement Costs Are Insane
How expensive is a mansard roof? Plan for $15,000-$30,000+ depending on size and materials.
Standard roof replacements might run $8,000-$20,000. Mansard roofs hit the top of that range or blow past it completely.
Why it costs so much:
The crew can’t walk on that steep lower section. They’re working from ladders the entire time, which is slow and dangerous.
Labor costs skyrocket because everything takes longer. Tear-off, installation, cleanup—all done while standing on ladders.
Premium materials of mansard roof cost more than standard asphalt shingles. Synthetic slate, natural slate, wood shake, or metal all carry higher price tags.
You need two different roofing systems—one for the steep sides, another membrane system for the flat or low-slope top section.
The complexity means you need experienced contractors who’ve actually worked on mansard roofs before. Not every roofer knows how to handle them.
What is the most expensive part of replacing a roof? On a mansard, it’s definitely labor.
The Disadvantages Nobody Warns You About
What is the disadvantage of a mansard roof? Several, actually.
Poor weather resistance: The flat or low-slope top section has terrible drainage. Water and snow sit there instead of running off, leading to leaks or even roof collapse in heavy snow.
High maintenance: That sitting water accelerates wear. You’ll see damage and leaks more frequently than with steeper roofs.
Limited contractor options: Most roofers don’t work on mansard roofs regularly. Finding someone experienced enough to do it right is tough.
Expensive repairs: Even minor fixes cost more because of the complexity and ladder work required.
Weight restrictions: You can’t just slap any material on there. Heavy options increase sliding risk and structural load.
How long do mansard roofs last? With proper materials and maintenance, 30-50 years. But that requires actually maintaining it, which people often skip because repairs are so expensive.
Modern Mansard Roof Design (Yes, People Still Build These)
Modern mansard roof designs are cleaner and simpler than historical versions.
Contemporary architects use straighter lines, larger dormer windows for more natural light, and metal roofing for easier maintenance.
The mansard roof house style works well for urban townhouses where vertical space matters more than horizontal sprawl.
You’ll see them in older city neighborhoods—Philadelphia, Boston, Washington DC—but rarely in new suburban developments.
Can you add a mansard roof to an existing house? Technically yes, but it’s wildly expensive. You’re essentially rebuilding the entire top of your home.
A mansard roof extension makes more sense than a full conversion. Add it to one section to create extra space without redoing everything.
Mansard Roof Construction Details Worth Knowing
Mansard roof construction requires precise planning.
The lower section needs to come out about two feet from the building before slanting up. This creates enough angle for water drainage despite the steep pitch.
Dormers are typically integrated into the lower slope for light and ventilation. These add complexity and cost but make the attic space actually livable.
The ridge at the top connects all four sides. Unlike a hip roof with one consistent pitch, the mansard has that dramatic angle change.
Mansard roof detail plans should show both the steep lower section and the gentler upper slope, plus how they connect at the angle break.
Do mansard roofs need gutters? Absolutely. That lower section dumps water fast, and the upper section needs drainage for sitting water.
Solar Panels and Energy Efficiency
Can you put solar panels on a mansard roof? On the upper low-slope section, yes. The steep lower sides? Not practical.
The upper section’s gentler angle actually works well for solar panel installation if oriented correctly.
What is the 33% rule in solar panels? Panels should be installed at roughly 33% of your latitude angle for optimal year-round production. For mansard roofs, that upper 35-degree section is close to ideal for many locations.
Which roof type is the most energy efficient? Mansard roofs can be efficient because that extra attic space acts as an insulation buffer. But only if properly sealed and insulated.
Planning Permission and Regulations
Do I need planning permission for a mansard roof? In most areas, yes—especially for new construction or conversions.
A mansard roof extension definitely requires permits. You’re changing the roof line and adding livable space, which triggers building codes and zoning reviews.
Historical districts have even stricter rules. Your mansard roof design might need to match surrounding architecture.
Check local regulations before assuming you can build one.
Alternative Roof Styles to Consider
What is another name for a mansard roof? French roof or curb roof.
What is the opposite of a mansard roof? Probably a simple gable roof—single slope on two sides, flat gable edges, minimal complexity.
What style of house has a mansard roof? French Second Empire, Victorian, Tudor Revival, and some Colonial Revival homes.
If you want that extra attic space without mansard complexity, consider a gambrel roof or a steep-pitched gable with dormers.
Quick Answers You Actually Need
What is a mansard roof?
A mansard roof is a four-sided roof with two slopes on each side, where the lower slope is steeper than the upper, creating extra living space.
What is the purpose of a mansard roof?
Creates extra livable attic space without expanding the building’s footprint.
What is the disadvantage of a mansard roof?
High replacement costs, poor weather resistance, and expensive maintenance.
What is the difference between a gambrel and mansard roof?
Gambrel has two sides with double slopes; mansard has four sides.
What is another name for a mansard roof?
French roof or curb roof.
Do mansard roofs need gutters?
Yes, for both drainage sections.
How long do mansard roofs last?
30-50 years with proper materials and maintenance.
Do I need planning permission for a mansard roof?
Usually yes, especially for extensions or conversions.
What is the weakest roof to wall connection?
Toe-nailed connections without hurricane straps or structural brackets.
What is the best material for a mansard roof?
Synthetic slate, natural slate, metal, or cedar shake for steep sections; membrane systems for flat tops.
What style of house has a mansard roof?
French Second Empire, Victorian, Tudor Revival styles.
Which roof type is the most energy efficient?
Varies, but well-insulated mansard roofs can be efficient due to attic buffer space.
How expensive is a mansard roof?
$15,000-$30,000+ for replacement depending on size and materials.
Can you add a mansard roof to an existing house?
Yes, but extremely expensive—better as a partial extension.
Can you put solar panels on a mansard roof?
Yes, on the upper low-slope section.
What is the most expensive part of replacing a roof?
Labor costs due to complexity and ladder work.
Does a mansard roof have more than one slope?
Yes, two distinct slopes on each of the four sides.
What Actually Matters About Mansard Roofs
Look, mansard roofing are gorgeous. That classic French architecture turns heads.
But they’re expensive to install, expensive to maintain, and expensive to replace.
If you’re buying a house with one, budget for that eventual roof replacement. It’s coming, and it won’t be cheap.
If you’re building new or adding one, understand you’re choosing aesthetics over practicality. Nothing wrong with that—just go in with eyes open.
The extra attic space is legitimately useful. Just make sure that benefit outweighs the lifetime costs of maintaining that complex double-sloped design on all four sides.
