3 Mansard Roof Design Tips

The mansard roof was created by Francios Mansart, a famous 17th century architect, who was looking to add extra room to the top of a house.  He was successful in creating a dual-pitched roof that would allow for an entire floor of living space above the cornice line of a home or other building, without actually adding to the technical number of levels in the structure.  A mansard roof is typically less expensive to build than any other roof style because framing is not needed.  The distinctive Mansard roofs have two slopes on each of the four sides of the roof line. Dormer windows are usually seen on the lowest slopes, which are steeper than the higher slopes. Most mansard roofs are made with shingles or slate.  There are three specific mansard roof designs available, explained below with tips for each style.


A concave style mansard roof will curve in, or is sometimes flared. Some of these roofs will have a steep angle on the bottom slope.  The concave mansard roof was very popular in the 19th century, especially the second half, and can be seen on large buildings and mansions.  Because the top of a mansard roof is flat, heavy snow accumulation can cause cracks, which will leak, and lots of rain can cause water to pool and erode the roof.  The best thing for a homeowner with a concave mansard roof to do is to check the roof thoroughly for damage at least once a year.  Repair any damage immediately so that it does not get worse and cause more expensive damage.


The convex style of mansard roof describes the outward curve on the lower slope.  Convex mansard roofs can be shaped like the letter S, or may have a bell shape. Both of these shapes, and convex mansard roofs of all types, allow more interior roof space without having to add an additional level to the building. Mansard roofs with convex shaping are typically found on courthouses with fancy towers.  If your home has a convex mansard roof, remove any tree branches that come within 5 feet of the perimeter of the house, and all branches that hang over the roof.  This way, no tree branches will fall onto the flat roof. If one does, it could sit there for a while until you can remove it, and it can cause damage to the roof.


A straight mansard roof has a slight slope on the upper panel that is not usually visible at ground level.  These roofs are designed to feature dormer windows in the slower slope, which can sometimes be almost vertical. These dormers provide ventilation, light, and extra interior space.  One disadvantage to having a straight mansard roof is that the weight of snow can cause cracks, which will create leaks from the roof’s surface.  When repairing an old roof, try and bring the original piece to the store with you. Sometimes items are no longer made, so you will want to be able to match it to existing products to get the closest match as possible.