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What Is a Mansard Roof? Pros and Cons, Designs, Costs

In the process of building a new home, choosing the right roof is one of the most important decisions you will need to make. The roof over your head has to not only give your home the protection it needs, but also the looks and features that you want to have. 

Source: homedit.com

The mansard roof is one of these options. Popularized in France in the 17th century, this roof style is characterized by its tall, vertically spacious structure and its distinctly elegant look. 

So what does the mansard roof have over other, more modern styles? What are the costs and caveats we need to look out for?

We will explore all this and more in our detailed guide to mansard roofs.

What Is a Mansard Roof?

In the vast and rather confusing taxonomy of roofs, a mansard roof can be best summarized as a combination of a hip roof and a gambrel roof. To better explain what this means, let’s break it down. 

A gambrel roof is the type of roof you may recognize from traditional barns; it is a two-sided roof with two slopes on each side, the lower slope being steeper than the other. Meanwhile, a hip roof is a four-sided roof with slopes of standard height. These two characteristics are combined to make a mansard roof.

Although sources agree that the design was likely developed in the 16th century, the mansard roof shot up in popularity thanks to the work of French architect Francois Mansart, from whom the roof design actually gets its name.

Advantages of a Mansard Roof

#1. Large attic space.

As we will recall, the mansard roof has two slopes on each side, with the lower slope having a higher (and almost vertical) inclination compared to the higher slope. The result of this is the creation of a much larger attic space than is possible with most other roof types. 

In fact, the extra vertical space is such that the mansard roof is typically built with dormer windows to provide a natural light source for the attic as well as add visual interest to the otherwise bare roof. 

#2. Easier vertical expansion.

The vertical design of the lower slope of a mansard roof means that the roof structure is easier to modify and repurpose into a support structure for an upper floor. 

For this reason, a mansard roof could be preferable to have if you wish to expand your home with an additional floor sometime in the future.

#3. Distinct aesthetics.

Although not all things that are French are immediately elegant or fancy, there is no denying that the distinct look of the mansard roof will give any home a dash of French aesthetic appeal that is difficult to pull off with any other roof type. 

Disadvantages of a Mansard Roof

#1. Lower weather resistance.

Compared to the slopes of, say, a gabled or a typical hipped roof, the slopes of a mansard roof can make it more vulnerable to difficult weather. 

The vulnerability of the mansard roof could mostly be attributed to the very low (if not practically flat) incline of its upper slope, which can have a hard time clearing away rain or snow accumulation. If left unchecked, the buildup of snow or standing rainwater could cause lasting damage to the roof surface and, in turn, its internal support structure.

#2. Higher installation costs.

It should be a surprise to no one that mansard roofs are not a very common design choice among houses nowadays. For this reason, it can be difficult to find contractors that are both willing and able to build a mansard roof with an acceptable standard of quality. Naturally, the contractors that do will likely charge quite a bit for the privilege. 

#3. Higher repair and maintenance costs.

Anything that has high construction costs will typically cost more than usual to repair and maintain in the long run, and mansard roofs are no different. 

As in the case of installation, maintenance costs of mansard roofs are higher than that of other designs because they are not as common. As such, the few contractors that are willing to do the work will charge more to do it. 

Mansard Roof Design Variations

Like other roof designs, the mansard roof has multiple variations that each has its pros and cons. From a general standpoint, there are 3 basic variations of the mansard roof, which we’ve listed below:

Straight Mansard Roof

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The upper slope of the straight mansard roof has a gentle incline, although it is not often obvious to those who are gazing up at the roof from ground level. The bottom slope is almost entirely vertical and typically has dormer windows, which not only give air and light but also some additional living space.

Convex Mansard Roof

Source: homedit.com

The lower slope of a convex mansard roof is curved outward, giving it the appearance of either an S-shape or a bell shape depending on how it is constructed. The convex design increases the amount of usable space inside the roof, giving you an attic space that is almost like a new floor without actually needing to build one.

Concave Mansard Roof

Source: flickr.com

The bottom slope of a concave mansard roof has a sharper angle than the other two, and the design features an inward curve that flares outward at the edge. The inward curve naturally reduces the usable space inside the roof, but makes up for it with its arguably more elegant look that resembles traditional French homes.

How Much Does a Mansard Roof Cost?

The cost of a mansard roof, like any other roof design, mostly depends on the materials used on it. As we have previously established, however, the labor costs do make this shoot up quite a bit in price over other designs.

You can expect a mansard roof to cost anywhere from $10 to $25 per square foot of roofing, accounting for the average costs of both labor and materials. This can work out to up to $50,000 at the high end for a roof with 2,000 square feet of roofing.

Of course, depending on where you live and what is available, you may find the cost in your area higher or lower than the range we provided. 

Meanwhile, some homes may allow you to perform what is called a mansard roof extension, giving you extra living space inside the mansard roof’s attic. However, since it is effectively replacing your roof with a mansard roof, you can expect the cost estimates to be around the same. 

Can a Mansard Roof Be Replaced?

Generally speaking, yes, a mansard roof can be replaced or changed with either a new mansard roof or some other design of your choice. The only limiting factor to this, really, is the cost; as such, you will want to weigh your options carefully. 

How to Install a Mansard Roof

as doing the same with any other roof design out there. The only real difference lies with the structure of the roof itself.

The building process begins with the mounting of the mansard roof joists on the house’s roof frame. From here, the mansard roof framing details are built according to the selected style—straight, convex, or concave, as previously mentioned.

Once the frame has been built completely (including the provisions for the dormer windows), other mansard roof construction details are added in as in any other roof design. This includes insulation and any electrical or plumbing pathways that you may want to install. 

The process is topped off with the installation of the roof sheathing, shingles, flashing, and trim that complete the mansard roof.

How To Insulate Mansard Roof

Insulating a mansard roof, under ideal circumstances, should be done as it is being constructed, in which foam insulation is installed into the space between the attic wall and the actual frame of the mansard roof.

By comparison, it is a lot more difficult to do the same on a mansard roof that is already completely built because there is no longer any easy access to the target space. 

Insulation, however, is not impossible—thanks to spray foam and poured-in insulation options, one can drill small holes at strategic points in the attic walls, through which insulating material can be piped in.

How to Shingle a Mansard Roof

Because of its distinctive steep slope, installing shingles on a mansard roof can be quite challenging if you don’t have the right tools to position yourself safely and comfortably. For this reason, we would suggest hiring a professional to shingle your mansard roof to produce the best results.

If you wish to go down the DIY route, however, here are the steps to shingle your mansard roof yourself:

  1. Choose a corner to place your first shingle. You will want to follow a path back and forth across the length of the roof from the bottom row to the top. 
  1. Cut the tabs from the initial row of shingles and position them along the edges.
  1. Fasten each shingle with four to six nails (using more nails if the roof slope is steeper), then seal them down with plastic cement. 
  1. When beginning the next row, align it with the previous row and then proceed upwards. You want them to overlap slightly while still being installed properly and securely. 
  1. Once you reach the peak, you can go to the opposite side of the roof and start the process over.

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