The mansard loft conversion takes its name from a French architect, Francois Mansard who was prominent in the 17th Century. Unlike other types of attic makeover, this one is generally constructed to the rear of your property. There are a number of other elements that set a Mansard apart from standard loft conversions.
There is only one of roof that is available with a Mansard, and it's a flat roof. However, it does feature a back wall which has to slope at a 72 degree angle
Most loft conversions don't require any planning permission unless the are 40 cubic metres in a terraced property or 50 cubic metres in a semi-detached or detached property. However, the Mansard is different and will require permissions. This is because it completely alters the overall shape and structure of your roof
Pros and Cons
One the plus side:
However, the negatives are:
Of all the different type of loft conversions that you could opt for, this is perhaps the one that will offer the most long term satisfaction because it blends into your existing house. The mansard is the most expensive of all the conversions, but it has the advantage of using your roof space to its fullest potential.