Mansard Roof; How to Build and Its Advantages & Disadvantages

Mansard roof are otherwise known as French roof designs. This style of roof or curb roof includes a four sided hip roof style with two distinct slopes.

The steeper angle can be found on one side, and the window creates an extra floor of space in a home, called a garret.

Some of the first examples of this style roof are credited back to a French designer named Pierre Lescot.

This style of roof was used on parts of the Louvre built around 1550. The roof became more popularized later on into the 17th century.

1. What is Mansard Roof Mean?

Mansard means the attic or space inside the roof structure rather than just the shape of the roof. Due to its design in the extremely close to nature of this attic space, a mansard roof is very efficient in terms space management and the format is related to green roof design.

While this is not a style that you commonly find in many modern homes, it does often come into the framing of French style construction details because of which people choose this style to emulate this look from past.

During the extension of the home, people use this design too often because it is gaining more traction in modern design.

While installing these roofs can be an excellent idea for giving your renovation a smart touch. Mansard roofing structures are still an ancient construction, but these roofs and their construction details are ideal for getting more out of your home.

2. A History Lesson on Mansard Roofs

Although, the creation of the Mansard roof is credited to François Mansart (1598 – 1666) he was not the first one who used this style.

That honor would have to go to Pierre Lescot (1510 – 1578) who used this roofing style on a part of the Louvre Museum in the year 1550.

However, it was not until the early 17th century that the Mansard roof architecture became popular.

François Mansart, who was an accomplished architect of the French Baroque period, started adopting this roof style into the buildings he designed for his clients.

Thus, this roof architecture was christened as the Mansard roof in his honor.

Interestingly, in Europe, Mansard can also refer to the attic space and not just the roof structure. The popularity of the Mansard roof kept on growing in France and became even more fashionable during the reign of Napoleon the 3rd (1852–1870).

During this time, the Mansard roof style spread across the world and was adopted in different buildings of United States, Canada, and many other western countries.

Mansard roof was not used quite as often in traditional homes despite it was featured in many high-rise residential buildings, especially in the late 1960s and 1970s.

Later on, many small commercial buildings also adopted a Mansard style roof. However, unlike a traditional Mansard roof, these roofs had a flat top.

3. Mansard Roof Detail

Mansard roof detail
Mansard roof detail

The mansard is particularly well suited to renovation work on pitched roof houses because the upper story can be enlarged without adding extra height to the structure.

The low downward slope of the mansard roof line acts visually to reduce the scale of a building and helps to eliminate a boxy appearance.

This technique is used frequently on large commercial projects, particularly those near residential neighborhoods. It is also a common solution to the problem of avoiding a monotonous appearance on flatroofed frame apartment buildings.

Properly used, a mansard roof can strengthen the design without substantially increasing construction costs. If raised up above the level of a built-up roof the mansard can screen out roof penetrations or mechanical equipment.

The variety of mansard roofs is practically infinite. One of the most widely used (and misused) roof designs, its proportions and scale are very important and care should be taken to avoid a mansard roof line that is either too skimpy or too generous.

Two of the most widely used roofing materials on the mansard roof are Certi-label cedar shakes and shingles.

Cedar shakes, with their heavier texture and solid appearance, are perhaps more frequently specified for mansards although shingles are also used, particularly when a lighter scale is desired.

The light weight and ease of application of Certi-label shakes and shingles contribute substantially to economical construction. Construction details for typical mansard roofs are shown in Figure 6.

Top of Mansard Roof – Coping Cover

This detail shows a condition where the top of the mansard meets a coping cover. The top edge of the pans are folded out to the height of the standing or batten seam, then bent down 3/4″. The coping cover is hooked over this edge, effectively forming a drip.

Top of Mansard Roof - Coping Cover

Top of Mansard Roof – Gravel Stop

The top of a mansard at a gravel stop is illustrated. The top edge of the pans are treated similar to Top of Mansard Roof – Coping Cover, with the gravel stop engaging the folded pan edge.

Top of Mansard Roof - Gravel Stop

Bottom of Mansard Roof

This is a typical condition for the lower edge of a mansard. The bottom edge of the pans are hooked over the edge strip to form a drip. The horizontal dimension of the edge strip should not exceed 4″ if it is not fastened to the soffit.

Bottom of Mansard This is a typical condition for the lower edge of a mansard. The bottom edge of the pans are hooked over the edge strip to form a drip. The horizontal dimension of the edge strip should not exceed 4" if it is not fastened to the soffit.

Change in Mansard Roof Slope

This detail shows the condition where the bottom of the mansard meets another roof. At the lower roof, the standing seams are laid flat 8″ from the roof break, folded 3/4″ and secured with copper cleats spaced 12″ O.C.

Copper locking strips of the same weight as the flashing are soldered to the pans between seams at least 6″ from the roof break and engage the base flashing in a 3/4″ lock.

At the upper roof, the upper edge of the base flashing is folded 3/4″ and secured with copper cleats spaced 12″ O.C. A continuous locking strip is soldered to the base flashing and secures the mansard roof edge.

Change in Mansard Slope This detail shows the condition where the bottom of the mansard meets another roof. At the lower roof, the standing seams are laid flat 8" from the roof break, folded 3/4" and secured with copper cleats spaced 12" O.C. Copper locking strips of the same weight as the flashing are soldered to the pans between seams at least 6" from the roof break and engage the base flashing in a 3/4" lock. At the upper roof, the upper edge of the base flashing is folded 3/4" and secured with copper cleats spaced 12" O.C. A continuous locking strip is soldered to the base flashing and secures the mansard roof edge.

Continuous Over Roof Batten Detail

The detail illustrates the installation for batten seams which are continuous over the roof. Standing seams under the same conditions are detailed in a similar method.

Continuous Over Roof Batten Detail

4. How to Build a Mansard Roof?

What you will need?

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  • Woodworking tools
  • Dumpster
  • Ladders
  • Working gear: knee pads, gloves, tool belt, hard hat, and boots
  • Sheathing
  • Scaffolding
  • Blueprints
  • Shingles
  • Underlayment material
  • Lumber
  • Plastic sheets and tarps
  • Hardware
  • List item


5. Build a Mansard Roof Step by Step

A mansard roof is an excellent addition to a home for those looking to increase the living space on the top floor.

Building a mansard roof at home is a fairly easy task provided one has the correct design, appropriate instructions, quality building tools and the requisite technical and manual skills.

Step 1: Decision Making and Planning

This step involves choosing a blueprint for the roof you wish to build, by contacting local authorities to find out the area-specific building codes and regulations, dealing with contractors to find out the details of the building process, purchasing all the supplies, hiring out labor if the job is too much to finish alone and taking out an insurance cover to protect against any damages incurred during the building process.

Step 2: Preparing the Building Site

The first step in the actual building process is to get the area ready for construction. Start out by choosing a specific place for all the tools you will need.

Use a large table or a portion of the lawn so that all the materials are in one place, easily accessible and neatly arranged.

Remember to cover all plants and any appliances, fixtures, and machinery in the area with tarps or plastic sheets to prevent any damage during the construction.

Step 3: Placing the Rafters

Take the common rafters and fix them to one ridge board. Use the nails to fix them in place. Once this is done, elevate the ridge and then use nails to fix the other rafters into place as well.

The outside rafters have to be placed such that the bird’s mouth is on a plane with the highest plate of the wall.

Once the precise position has been achieved, use nails to tighten the rafters into place. The same procedure has to be carried out on the three remaining sides.

Step 4: Remaining Common Rafters

The common rafters left over from the third step now have to be fixed into place. They too have to be nailed into place to ensure a tight and secure positioning.

Step 5: Ceiling Beams and Sheathing

The ceiling beams have to be fixed with care. Use nails to secure them in place and ensure they aren’t loose so that there is no damage later.

After this has been done, cover the area with the sheathing.

Step 6: Upper Extension

The elevated extended region that forms the upper extension of the mansard roof has to be built using vertical rafters. These vertical rafters have to be placed within the boundaries of the ridge board.

Common rafters should be used on both the inside and the outside of this structure to lend it strength and support.

Step 7: Sheathing and Shingling

Use collar ties and fascia for the roof before the sheathing process can begin. The sheathing material has to be attached to the common rafters using nails.

Regions, where there are valleys and vents, should be covered using flashing. After this has been done, one should lay the undercoating material over the entire surface and then cover it with the shingles.

6. How to Frame a Mansard Roof?

What you’ll Need?

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  • Wood
  • Pen
  • Paper
  • Screwdriver
  • Screws


A mansard roof is a commonly seen roof type and is visible on old-style houses and modern ones, it can even be used in barnyards and dog houses.

Completely versatile, this form of a roof has two parts, the lower of which has a deep slope to each of the sides, and the upper portion is further back, almost vertical in direction.

The use of the mansard roof in homes is popular as it allows for more living space, and you do not need to frame it in order to get it to work.

However, should you choose to frame your roof, and then you can follow a few simple guidelines for getting the project completed quickly.

7. Frame a Mansard Roof Step by Step

Step 1 – Designing the Frame

The first step in creating your mansard roof is to design the frame in pen and paper. You will need to have two stages to the construction, with the larger frame going on before the smaller, higher one.

In order to get the right angle for your frame, start by drawing a semi-circle on a piece of paper. You will need a tall support at the center, so draw a line from the top of the circle to the line at the bottom.

Then, take your paper and fold it so that the lower line of the semi-circle reaches the top of the support line.

This fold will divide your smaller roof from the larger. You can now draw in a smaller roof with shallower sides on top, and the lower, shallower roof below.

Step 2 – Begin the Build

With this basic design in mind, begin your framing by building a horizontal line, as wide as you want the lower part of the roof to be.

Now, a long piece of heavy wood, and place that in the center. Screw all the pieces into position. You now have the basic support structure for your roof.

Step 3 – Make the Lower Roof

You should then take wood, and cut it to the length desired for your lower roof. You need four support posts, one at each corner.

Frame the roof by laying boards between each of the four posts until you reach the top of the posts.

You should then take four more pieces of wood, and create another horizontal support, as on the bottom of your roof.

Nail each of the framed pieces of wood together, or screw in place, before proceeding.

Step 4 – Make the Upper Roof

Take four more pieces of wood, and screw them into the corners. You can then bring them across so that they touch in the center.

Fit all of these lengths together, so that you have a basic pointed roof. Now, add you’re framing timbers along the sides, until you have reached the top of the roof again. You have now finished the roof.

8. Advantages and Disadvantages of Mansard Roof

Advantages of Mansard Roofs

1. Future Additions:

Because the first slope of a mansard roof is so steep, it can act as a wall if you ever decide to build another floor on top of your home.

This allows for greater flexibility in the long run and makes it cheaper to have such additions done in your home.

As a result, mansard roofs are ideal for young couples who are looking to raise a family, but who do not want to purchase a large home right away.

2. Added Space:

Even without building an addition on top of your already existing roof, mansard roofs provide extra living space when compared to other types of roofs.

Because all four sides of the roof are steeply sloped in a box shape, it is easy to convert the attic space into a loft or an extra bedroom if needed.

3. Aesthetical Value

Although looks are subjective, there is no denying the fact that Mansard roofs have an elegant design, largely due to the fact that they were an important part of French architecture during the Renaissance period.

Moreover, in areas where they are not commonly found, this roofing style will definitely look more sophisticated and might even be a head turner, if executed properly.

Disadvantages of Mansard Roofs

1. Cost and Installation Time

Mansard roofs cost more and take longer to install when compared to other types of roofs. The process of building a mansard roof is fairly complex and requires more labor and materials when compared to normal gable roofs. This can be prohibitive for homeowners operating under a tight budget.

2. Weather Resistance:

Mansard roofs are not ideal for areas that receive heavy amounts of rain and snowfall because the second, flat slope on the upper portion of the roof does not allow for rapid drainage of runoff.

This means that large amounts of water can end up standing on your roof, which can cause leaks and mold growth inside your home.

3. Maintenance:

Mansard roofs require much more maintenance when compared to traditional gable roofs because the flatter portion of the roof collects debris much more rapidly and as such is more susceptible to damage.

Though the maintenance is not necessarily grueling or expensive, it is fairly constant, and as such can be a hassle that drives up the long-term costs of your roof.

4. High Installation Costs

After you check out a few illustrations of the Mansard roof, the first thing that will be apparent is the complexity of the design.

Naturally, that will lead to a high installation cost. In fact, you will be able to install multiple Gable roofs or Hip roofs for the cost of a single Mansard roof.

Moreover, not many roofing experts will be familiar with this design. Hence, the quality of the Mansard roof might not be up to preferable standards.

9. Images of Mansard Roof Construction and Architecture

Slate mansard roof with straight sides

Slate mansard roof with straight sides

Dormers have semicircular stone pediments, large keystone, and carved pilasters. Note oxidized roof cresting and parapet.

Mansard roof with pedimented, through-the-cornice dormer

 Mansard roof with pedimented, through-the-cornice dormer

Straight: Watson House /Buffalo Club

Straight- Watson House :Buffalo Club
  • Pedimented dormers
  • Keystone in round-arch window surrounds
  • Two-over-two double-hung sash.
  • Upper sash has rounded glass
  • Windows flanked by pilasters

Mansard roof (straight) with dormers

Mansard roof (straight) with dormers

10. Conclusion

Before we bid adieu, let us end this article with a word of advice. Although Mansard Roofs may look sophisticated and in many cases ostentatious, they are not very practical, especially if you are considering installing it in your home.

They are a piece of architectural heritage, and while that may be a tempting reason to use this roof in your home, we would advise you to choose the roof type very carefully with your regions climate in mind.

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