What about a Mansard Roof? FAQ’s Answered and More Questions Invited

Mansard roofs are near-vertical roofs that cover the top portion of a building. In many cases, a low slope roof covers the building above the mansard. I have found that metal shingles are often an excellent choice for mansard roofs, and address the unique challenges to property owners and contractors that this style of roof presents.

Examples of older home styles with these roofs are Chateau and Victorian. Victorian home architects and builders wanted a flat roof that could be used as a place to see what was approaching, often called a “widows walk”; mansard roofs were crafted below these spaces to dress things up.

There are also a lot of mansard roofs on homes and multi-family buildings built in the ‘70s and ’80s, which were and still are sometimes considered contemporary design.

A mansard roof is common on flat-roofed office buildings, multi-family projects, and retail establishments where this style is either incorporated to enhance the design, or constructed to manage flat roofs.

I think a big difference is that, on a mansard roof, the steep portion is almost vertical, and the upper low roof is flat or nearly flat, whereas gambrels are more of a transition between a steep slope and a less steep slope roof.

Gambrels often have the same challenges as mansards, though perhaps not quite to the same extreme because the pitch isn’t as steep. Gambrels also often can use the same roofing material on both roofs, whereas, with mansards, usually, you have different materials on the steep and low slope roof portions.

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Accessibility is a considerable cost factor when determining how much a mansard roof costs, beyond the actual cost of materials chosen. If the mansard can easily be accessed, the roof installs similar to siding and is fairly easy using ladders, walk boards, pumpjacks, and other access tools. These jobs would price out similar to typical roofs. However, if access to the roof is trickier and requires sophisticated scaffolding or perhaps an articulated lift, the installation is slower and more tedious, and therefore more expensive.

How the windows are inset or protruding from the mansard makes a big difference, too. Especially on protruding windows, re-roofing is the right time to perhaps re-trim those windows, so they look nice and do not require painting and other maintenance.

With these installation issues in mind, it’s even more important that you consider the lifetime cost of the roof replacement project.

Windows and doors in a mansard roof either protrude from or are recessed into the mansard roofing structure.

Typically, recessed windows and doors are easier to flash around and present fewer challenges with a new covering on a mansard roof.

However, mansard roof experts can always figure out these challenges, and we often support these projects with custom flashing made at the factory. Re-roofing a mansard-style home or building can be an optimal time to replace windows and put new, maintenance-free trim around them. Sometimes, on windows that protrude from the mansard, the roofing material will be used on their sides as well.

Learn how a Contractor solved the problem of replacing doors and windows in a multi-family project that included a mansard roof. Here’s the case study.

Windows that extend or protrude from a mansard roof require a weathertight covering on top. Usually, the area on top of the windows is relatively flat, making it a great candidate for a single piece of metal covering that will be durable and maintenance-free. This often works much better than something like roll roofing or small pieces of single-ply membrane.

Replacing and fixing these trims and seals when re-roofing is always a good idea. (See the question on the cost of a mansard roof in this article.)

What about handling problems with drainage from an upper roof on a mansard style?

Drainage from upper roofs is best if controlled by gutters. However, not all mansard roofs were built to accommodate gutters at the base of the upper roofs. In those cases, we look for ways to channel the water away from the mansard roofs or distribute it over a wide area.

In most cases, these roofs are boxed-in attachments to the sides of the buildings, and there is a typical encapsulated wall space between the mansard box and the living space. In some cases, though, extra insulation in the mansard box is desirable due to walls that are uninsulated and difficult to insulate.

For energy efficiency, it’s wise to make sure the wall behind the mansard box is insulated.

One common complaint of mansard-style buildings is they look dated. In some cases,  mansard styles have the timeless look of Chateau or Victorian architecture. In other cases, they look like inferior mid-century modern design, and owners look for a change.

When windows are inset, it may be possible to remove the mansard altogether.

With protruding windows, an option is to box in the mansard by creating walls that run plumb from top to bottom rather than be sloped. This can create a more contemporary look with clean, straight architectural lines.

With temporary roofing materials, such as asphalt shingles, colors beyond gray or brown are not available, and often trap a mansard roof building design within earth tones and the look of 1970s style.

Fortunately, lightweight aluminum shingles and panels address both the issues of gravity and color for mansard roofs. Not just a commercial red or blue, a variety of colors and finishes are available to work well with and enhance the other building materials of the home or structure. This is especially helpful in creating curb appeal through the accenting of brick structures or adding historical detail to Victorian and Chateau-style architecture.

The near-vertical angle of mansard roofs presents real challenges for roofing materials that depend upon gravity or failure-prone sealants to stay in place. Over time, the roofing can separate or cul and then crack and fall out of place. This can be very dangerous to occupants of the building, especially in the case of heavy slate or tile materials. Switching to a roof covering with interlocking panels is an ideal solution to mansard roofs and their susceptibility to the laws of gravity.

The hollow box behind this style of roof can be a welcoming space for unwanted critters such as squirrels, raccoons, or woodpeckers. This tends to happen once the roof has started to rot, providing ingress for the unwelcome guests. Protecting a mansard and its trim areas with metal goes a long way in stopping these building invasions.