The early years and the turn of the century will probably go through the minds of many people when they see a mansard roof. The establishment of the roof shape goes back much further in history. However, in its well thought-out construction it has lost none of its topicality to this day. We explain the advantages and disadvantages and provide helpful information on the construction.
Form and origin
The mansard roof was created in the 16th century. and 17. Century, where it was used to give representative townhouses and palaces a balance between wall area and roof. Like the Belle Etage, it lined up in the 19th Century then entered the almost compelling canon of the upper-class architectural language. Ultimately, a mansard roof is a Gable roofwhich, with a roof surface that becomes steeper in the lower area, slips over the top "normal" storey. Looking at it the other way around, you could say that a mansard roof is created when you look at the roof surfaces the outside bends to create a further storey in the attic with full-fledged rooms with straight walls accommodate.
function
Today the mansard roof has another function that should not be neglected in addition to its design effect. Numerous development plans use the number of floors and the eaves height to regulate the amount of structural use of an area. By accommodating the top floor in the roof, - in the
In contrast to the classic saddle roof - a much more usable floor can be gained than would ever be the case with a saddle roof. The classic stylistic device of the mansard roof thus gains a new meaning in order to exhaust the requirements of building planning law.The construction
In terms of construction, the mansard roof is always a purlin roof. Due to the roof surface, which kinks upwards, the rafters cannot run from the eaves to the ridge and thus cannot support themselves against each other. As a rule, the attic storey is integrated into the roof structure as a wooden framework. The central purlin rests on these walls, which also serves as a threshold for the flatter upper roof. Depending on the use, the studs can be lined up to full-fledged walls, so that one only becomes aware of staying in the attic when looking out of the windows. By setting up a floor-to-ceiling knee-high, even the steep incline of the roof is not perceived from the inside. At the same time, the steep roof slope allows the installation of normal facade windows and thus unrestricted good lighting and ventilation of the rooms.
The static challenge
Particular attention is paid to the statics in the construction of the mansard roof. The underlying classic gable roof directs the loads acting on the roof surface via continuous rafters to the outer walls of the building and from there
over the foundation components into the ground. In connection with the outer walls or an additional stiffening beam layer, this results in a stable static system in the form of a triangle. In the case of the mansard roof, however, the continuous rafter is interrupted and taken from a straight line by the outward kinking of the roof surface. In particular, the loads in the upper roof area develop a clear pressure downwards when the loads are transferred, and also outwards in the kink area. It is important to constructively absorb this external pressure and to prevent the roof from giving way. For this purpose, a layer of beams is usually installed above the attic floor, or several metal drawstrings are provided. Often these elements do not appear visually at all, as they disappear into the walls or ceiling of the attic floor.The roof pitch
Now there has already been talk of two different roof pitches and an upper roof and a lower roof. But which inclinations are best used? The assumption is obvious that the lower half of the roof must be steeper than the upper roof to achieve the characteristic roof silhouette. Slopes of at least 45 degrees are usual for the steep roof areas, but it makes sense to 50 degrees and more. It is not uncommon for inclinations of up to 70 degrees to be found in order to be able to use the interior space behind it as optimally as possible. The upper roof, on the other hand, can be inclined almost at will. In order not to create unnecessary and unusable space here, an incline of a maximum of 30 degrees is usually used, often even below that. On the other hand, a mansard roof in the ridge area hardly reaches below 15 degrees, as the traditionally used tile roofing only fulfills its function to a limited extent on flatter slopes.
NOTE: In the meantime, individual manufacturers allow the roof pitch to be reduced to up to 10 degrees. However, the optics should never be completely disregarded. The greater the difference between the two inclinations, the more difficult it is to achieve a harmonious design.
Advantages and disadvantages
Of course, the mansard roof doesn't just show
advantages
- Great gain in usable space in the attic due to the steep incline in the lower roof area
- Reduction of the unusable roof space in the rooftop due to a flatter slope in the upper roof
- Qualitative gain in the usability of the rooms in the attic through more vertical walls without large roof slopes and the usability of normal facade windows
- Gaining the "optical weight" of the roof, thus a more balanced design from the main structure to the roof is possible
- Advantages under construction planning law when limiting the height of the eaves and possibly the number of floors that can be read
disadvantage
- High constructive effort for the supporting structure
- Numerous detailed designs for window connections, changing the roof pitch, etc. necessary
- Classic roof coverings in steep roof areas with too high a slope are only possible with additional securing
- The usability of the roof spaces is better than a "normal" saddle roof, but still not a full-fledged storey
- In modern building planning law by stipulating the development plans, it can hardly be implemented without legal exemptions
The mansard roof today
The wedding of the mansard roof may be over, but it can still be found today in newly constructed buildings. However, not everything that looks like it is a real mansard roof. Because in order to take advantage of the optical and sometimes also building law advantages of the mansard roof without the constructive one Expensive to operate, are now often "normal" storeys in solid construction with an extremely steep roof surface disguised. The flatter, upper roof area is then added as a real roof structure, or is omitted in favor of one Flat roofs completely. To what extent the term mansard roof still applies here is ultimately up to the viewer. The fact is, however, that from a structural engineering point of view, little of the real mansard roof of earlier times has been preserved in these cases.
