A Mansard Roof, also known as a French roof or Curb roof, is a roof with four sloping sides that become steeper half way down. The lower, steeper slopes of a Mansard roof are more visible from the bottom of the building to give a flatter look from the ground to match the exterior of the building. Often designers will use a convex or concave slope on the steeper gradient to counteract the flatness of the shallower slope.
A Mansard roof is similar to a Gambrel roof in that each side of the roof has multiple gradients, however Gambrel roofs have just 2 sides while a Mansard roof has 4. Typically, dormer windows are installed on the lower, steeper slopes of the Mansard roof to aid the roof’s architecture and open up the space to become habitable. Having 2 slope gradients increases the usable space in the attic allowing it to be used for storage or to be converted into extra living space.
History of Mansard Roof
The first known use of a Mansard roof dates back to 1550 when Pierre Lescot designed the iconic Louvre museum in Paris. However, it wasn’t until the 17th century that the Mansard roof became fashionable. Francois Mansart is credited for popularising the design that is seen throughout Paris today, hence why the name Mansard roof is derived from his surname, Mansart.
This roof design hit peak popularity in France during the rule of Napoleon III between 1852 and 1870. That is not to say the Mansard roof was only popular in France, the design swept throughout Europe and eventually became popular in the USA and Canada. More recently, it can be seen on high rise buildings constructed in the 1960s and 1970s and smaller commercial buildings.
The traditional materials used to build a Mansard roof are slate tiles and wooden shingles. However more modern designs use zinc or copper shingles as they increase durability of the roof and reduce the long-term maintenance costs.
Mansard roofs aren’t only used for buildings, you can often find trains with Mansard roofs as they increase the usable space in the train car and allows passengers to stand up right without increasing the size of the carriage.
Advantages of a Mansard Roof
- More attic space – As mentioned above, the steeper slopes of the Mansard roof allow the attic to become a living space. This is good for hotels, apartment buildings or office spaces as it means there is less negative space in the building as well as allowing for an extra room in a family house.
- Easy to build on – The steep lower slopes of a Mansard roof are almost vertical meaning expanding the building upwards is much easier on Mansard roofs than alternative styles. This opens the opportunity for future extensions on the building making it excellent for urban areas.
- Better heat distribution – The heat distribution in a Mansard roof is more efficient than traditional roof styles due to its box-like shape. Using copper or zinc shingles further increases the energy efficiency of the attic space. Although the metal shingles are initially more expensive, the reduced maintenance costs and improved energy efficiency save money in the long-term.
- Attractive renaissance design – Due to its strong history in French architecture, the Mansard roof is a stylish renaissance design attracting real estate buyers and renaissance enthusiasts. Furthermore, the design is rare outside of France giving the building a feeling of exclusivity.
- Allow for more natural light – The almost vertical structure of the lower slopes means it is easy for windows to be built into a Mansard roof. Also, with there being more walls there is room for more windows creating an opportunity for there to be more natural light than in a typical attic conversion.
Disadvantages of a Mansard Roof
- Installation costs – The design of a Mansard roof is very complex meaning they take longer to construct and require lots of materials leading to higher installation costs. It is possible to use cheaper materials during installation to reduce the initial costs however this could lead to higher maintenance costs in the long run.
- Maintenance costs – As above, the maintenance costs of a Mansard roof are higher than a typical roof due to the complexity of the design. Also, the unusual shape brings different problems than usual to the roof maintenance, such as the flat top collecting more debris than usual leading to more regular clearing and maintenance. The maintenance costs can be reduced by using better quality materials during installation however this would further increase the installation costs.
- Poor weather resistance – The low pitch of the top slope of the Mansard roof leads to the roof being vulnerable to heavy rainfall and snowfall. A build-up of rain water on the flat top can seep through and cause leakages, while heavy snowfall may mean the weight of the snow on the roof results in a partial or full roof collapse. However, modern techniques use special materials and better insulation to prevent leaking and collapsing.
- Legal restrictions – If you are looking to construct a Mansard roof, it is wise to check local regulations and legal restrictions before you start. There are often restrictions on roof height and total building square footage that may lead to complications during construction that will take time and money to fix. When looking to buy a property with a Mansard roof, it is important to research the tax regulations and insurance costs associated with having the extra space.
- Finding a roofer – Finally, the rarity of Mansard roofs, especially those built in the last 30 years, means it may be difficult to find a roofer that specialises in or has worked on a Mansard roof before. This may mean higher costs or that roof is not constructed properly leading to problems further down the line.
Overall, Mansard roofs are practical for adding extra space to a building while retaining a stylish, renaissance design. However, the complex shape may cause issues during construction and be a more expensive option.