Mansard roof: types and insulation

The mansard roof is an architectural element that can be used to create cozy and bright spaces inside a house. This type of roof, characterized by a vaulted shape, can be used to create a bedroom or a study, offering additional space compared to the rest of the house.

Mansard Roof: What is it?

The mansard roof is a complex architectural element that derives from French Baroque. It owes its name to its inventor, the French architect François Mansart.

The mansard roof is based on the shapes of the hipped roof, the single-sloped roof, or even the double-sloped roof. Compared to these roof shapes, the surface of the mansard roof is not continuous, meaning it bends at a point. Below this bend, there is a steep slope of the roof. The mansard roof is supported by load-bearing beams and wooden trusses.

The lower part of the construction has a very steep roof pitch, around 70%, while the upper part has a roof pitch angle of around 30%. This characteristic allows the mansard roof to create more useful living space under the slopes compared to other roof types.

How should a mansard roof be?

The roof of a mansard must have specific structural characteristics to ensure regulatory compliance and the functionality of living spaces. The minimum height calculated from the floor to the ceiling for a habitable mansard must be 2.7 meters for rooms used as living rooms and 2.4 meters for service rooms, in compliance with national regulations.

Each type of mansard roof has specific structural characteristics that influence the perception of spaces and the functionality of living areas. To ensure a comfortable and bright environment, the mansard roof must be designed considering the installation of roof windows that allow the passage of natural light, ensure adequate ventilation, and contribute to the thermal comfort of the spaces. Lighting, along with ventilation, is a fundamental aspect to make the attic habitable.

Thanks to a building design software, you can create an optimal roof based on your requirements and needs.

Types of Mansard Roofs

Mansards present a variety of shapes and characteristics that influence the appearance and functionality of interior spaces. Unlike traditional apartments with horizontal ceilings and vertical walls, mansards offer a more articulated volume, determined by the shape of the envelope and the type of roof used.

There are different possible configurations for a mansard that, unlike conventional apartments with horizontal ceilings and vertical walls, offer a more varied volume, influenced by the roof shape, the type of covering, and its relationship with the spaces below. They include:

• flat roof;
• single-sloped roof;
• double-sloped roof (symmetrical or asymmetrical);
• curved roof.

The roof shape is crucial for the perception of the interiors. For example, a mansard with a flat roof, common in condominium buildings, can result from the renovation of technical rooms or communal washrooms. Compared to conventional apartments, it offers more natural light and a panoramic view of the city or surrounding landscape. The ceilings may be lower, but the installation of roof windows avoids the feeling of confinement.

A mansard with a single-sloped roof has a sloped surface, determining the sense of space based on the maximum and minimum height of the roof and the presence of windows. The internal layout and furnishings must consider the variation in ceiling height.

The double-sloped roofs, symmetrical or asymmetrical, characterize spaces with a ridge line along the entire apartment. Very common in residences, the mansard with a double-sloped roof offers various composition and usage possibilities, mainly determined by the position of the ridge line, where the two slopes meet. In the highest and central points, near the ridge line, furniture and functions accessible to people can be placed, while in the lower points on the sides, tailor-made storage solutions can be inserted. To ensure comfort and brightness, the installation of roof windows, sized according to the total surface area, is essential to make the attic habitable and well-lit with zenithal light.

The curved roof, less common than traditional types, is often associated with buildings not intended for residential use but mainly commercial or industrial. This particular shape can offer interesting ideas for creative and original transformation projects. Each case requires careful evaluation of the roof curvature, the heights below, the materials used for the covering, and the layout of the spaces below to create a comfortable and functional mansard.

Other roof types and combinations of those mentioned may be present. It is important that the design and furnishings take into account the specifics of each mansard. The presence of a double height further enriches the spaces, allowing optimal ventilation and natural lighting, as well as creating interesting volumetric effects.

Thermal Insulation of Mansard Roof

The mansard is a fully habitable floor, so thermal insulation of the mansard roof must also be considered. An appropriate stratigraphy must be designed to live comfortably throughout the year, avoiding heat loss, costs, and negative impacts on the environment.

In the past, the attic was mainly a storage space for various items and memories, but above all, it served as thermal insulation: protecting the living spaces below from the outside. Today, thanks to modern construction techniques, attics have been transformed into beautiful habitable mansards, requiring a complex stratigraphy to ensure comfort and energy efficiency.

The roof stratigraphy includes different layers, each with a specific function, which must interact synergistically to effectively meet the protection and thermal insulation needs of the building. These layers may include elements such as:

• thermal insulation;
• waterproofing;
• roof covering and weather protection.

The material layers of the mansard roof aims to ensure protection from the weather, heat retention, thermal insulation, effective covering, and waterproofing to preserve the quality of indoor environments and ensure living comfort.

Internal insulation of mansard roof

The losses that occur through the roof can account for up to 30-40% of total losses. The most commonly used techniques to insulate this component of the house are 3:

• external insulation (extrados);
• internal insulation (intrados);
• insulation on the attic floor (extrados of the last slab).

Internal insulation is the most commonly used solution for buildings with sloping roofs, equipped with a habitable attic, and for the wooden roofs of residential buildings during their renovation. In this case, insulation involves applying the insulating material from the inside.

Insulating the roof from the inside is an effective solution to achieve optimal thermal comfort inside the house. This type of intervention also leads to significant energy savings by preventing heat loss through the roof. There are several options to thermally insulate the roof from the inside, such as creating a drop ceiling or waterproofing the slats in the case of sloping wooden roofs.

Choosing the right insulating panels is crucial to achieve a good result. Some commonly used materials are rock wool, expanded polystyrene, wood fiber, and polyurethane foams. The drop ceiling is an excellent solution for thermal insulation of the roof from the inside, to be realized with pre-coupled plasterboard panels and insulating materials such as rock wool or cork. This solution adapts to both sloping and flat roofs, offering a versatile and functional alternative to improve the thermal insulation of the house.

Internal thermal insulation of the roof offers numerous advantages, including:

• reduction of heat loss and consequent energy savings;
• improvement of the building’s energy class;
• increase in the property value;
• elimination of issues such as cold, humidity, and drafts inside the house.

What is the difference between attic and mansard?

Although the terms “attic” and “mansard” may seem synonymous, there is actually a significant difference in terms of regulations, with important implications also from a commercial point of view.

An attic is the space between the roof and the floor slab of the residential unit located on the top floor of a building. This space is characterized by non-uniform volume, with wider and higher areas in the central part of the roof and less usable areas where the slope drops below 1.80 meters. Due to its poor natural lighting, the attic floor is not intended to be habitable according to regulations. The attic floor can be used as a storage space for unused items or to accommodate technical elements such as heating systems or tanks. Structurally, the attic floor is distinguished into two types: the “air chamber,” a space without a suitable floor to support the weight of people and things, and the “attic,” a non-habitable space but usable only as storage.

The mansard, on the other hand, is an attic space with characteristics that allow prolonged stay by people. The mansard must be created within the slope of the roof, with a normal slope in the central part (ridge) and a steeper slope in the perimeter part (eaves). For a mansard to be considered habitable and obtain a certificate of habitability, it must meet a series of minimum requirements established by regional laws, including:

• adequate average and minimum height;
• sufficient air and light ratio to ensure natural lighting and ventilation;
• primary urbanization requirements (water, gas, electricity, sewage);
• thermal insulation works to contain energy costs.

Renovating a mansard roof

Before starting the renovation of an attic to transform it into a cozy mansard, it is important to address several practical issues. The need to obtain permits for the renovation of the attic depends on the nature of the work to be carried out. Free building interventions, such as replacing a window without structural changes, usually only require a notification.

Before proceeding with the renovation, it is essential to verify that the attic meets the minimum requirements to be habitable. These include minimum heights for livable spaces, the air-light ratio, and local health and hygiene regulations.

Here are the fundamental steps to start the attic floor recovery project:

• contact a designer and verify the usable surface of the attic floor, respecting the minimum height requirements set by regional regulations;
• identify the type of intervention needed, assessing whether internal renovation is sufficient or if roof reconstruction is also required;
• check the permits required for the intervention, starting from the request for a building permit (in the case of change of use or increase in volume);
• define the project of the new mansard together with an experienced technician, paying particular attention to natural lighting.

How much does it cost to raise the roof of a mansard?

The cost of raising the roof of a mansard can vary significantly based on several factors. According to an estimate, we can indicate that the average cost to raise a roof ranges between €500 and €1,000 per square meter. However, it is important to consider that specific costs depend on the size of the intervention, the materials used, the complexity of the existing structure, and the desired finishes. To obtain a more accurate estimate, it is advisable to consult directly with a professional in the field who can assess the specific circumstances of the project.