The roof can appear in many ways. It is also able to create added value in terms of design or use for the most varied of roof shapes. Here you can find out useful things about the mid-roof, from construction to possible uses and additional, interesting information.
When a roof is between
First of all, one might be reminded of the dwarf in the concept of the mid-roof. This assumption would not be absurd either, since a mid-roof describes the roof of a transverse structure on a main structure with a main roof. Ultimately, however, "midway" does not mean more or less than "across", so that the mid-roof does not get its name from its dimensions, but from its orientation. In architecture, the concept of the mid-roof is actually only found in real transverse structures, i.e. subordinate structures that are clearly recognizable and legible at full height of the building.
Outside of the technical jargon, the term is also often found in connection with dormer windows, that is Superstructures that are surrounded on all sides by the main roof area and can only be read from the "attachment" on the roof are. The information given below can easily be related to both variants, i.e. to the roofing of real transverse structures and dormer roofs. Because both visually and technically, both cases are almost exactly the same.
The sense of a mid-roof
The reasons for using a mid-roof may be as individual as the buildings equipped with it. However, the objective added value of this roof element can be limited to two basic areas:
1. Optical added value:
- Subdivision, zoning and structuring of the main roof
- Reduction of the visual heaviness of the main roof through small, additional superstructures
2. technical added value:
- straight walls instead of sloping ceilings on the main roof for better furnishing
- greater room height for lounges, access or technology (e. B. Elevator) in the attic
The roof pitch
At this point, it is not about the inclination of the mid-roof itself, but about the required inclination of the roof surface from which the mid-roof should emerge. Theoretically, this is possible with any type of slope, but the roof surface must be larger, the flatter the slope. This is the only way to achieve the height difference required to accommodate the mid-roof through the pitch of the roof. The difference in height does not just have to be so high that the construction of the double roof disappears into it. In addition, there must of course be the additional gain in room height under the mid-roof reflect again and, moreover, a certain preservation of the main roof area around the mid-roof is possible be. This connection can be seen quite well in practical examples:
1. Roof pitch 45 ° / house depth 8 meters (normal single-family house) / central ridge:
- resulting height difference of the main roof area 5 meters
- Average roof construction height of the diaphragm with insulation etc. approx. 0.30m
- Minimum height of the lounge in the roof (depending on the federal state) approx. 2.20m
- Remaining height of the main roof with a mid-roof as Flat roof 4.00 meters minus 2.50 meters total height of the dwarf structure = 1.50 meters
2. Roof pitch 30 ° / house depth 8 meters (normal single-family house) / central ridge:
- resulting height difference of the main roof area 2.66 meters
- Average roof construction height of the diaphragm with insulation etc. approx. 0.30m
- Minimum height of the lounge in the roof (depending on the federal state) approx. 2.20m
- Remaining height of the main roof in the case of a dwarf roof as a flat roof, minus 2.66 meters. 2.50 meters total height of the dwelling = 0.16 meters
3. Roof pitch 25 ° / house depth 8 meters (normal single-family house) / central ridge:
- resulting height difference of the main roof area 2.22 meters
- Average roof construction height of the diaphragm with insulation etc. approx. 0.30m
- Minimum height of the lounge in the roof (depending on the federal state) approx. 2.20m
- Remaining residual height of the main roof with a dwarf roof as a flat roof 2.22 meters minus. 2.50 meters total height of the dwelling = -0.30 meters
It quickly becomes clear that even with a minimal construction height of the mid-roof as a non-sloping flat roof usual housing depths from an inclination of 30 degrees an area is reached where a mid-roof is barely there functions. If the mid-roof is now also higher due to a different roof shape with a slope, it can only be raised in the case of a higher inclination of the main roof or a correspondingly greater depth of the roof surface up to the ridge point realize.
Where a mid-roof works
Basically, a mid-roof, along with the transverse structure or roof structure connected with it, can be used anywhere Realize where it emerges from a sloping roof surface with the slope already explained can. However, its practical use shows that the usability is also subject to further restrictions.
Well suited for:
- Gable roofs
- Barrel roofs (with sufficient curvature)
- Mansard roofs
- Hip roofs and Hipped roofs with a large remaining roof area
Moderately suitable for:
- Smaller-sized hipped roofs and half-hip roofs (due to insufficient remaining roof area)
Unsuitable for:
- Pent roofs (as it is very difficult to reconcile the design with a clear design and the inclination is often not sufficient)
- Flat roofs (as there is no noticeable slope)
Roof shapes and coverings for the mid-roof
In fact, all common roof shapes and covering materials of modern residential buildings can be implemented with the mid-roof. Depending on the chosen Roof shape the mid-roof can either appear imposing or restrained in the
Insert main roof area. Just accept a few restrictions:- The direction of the ridge for saddle, hip or barrel roofs is always orthogonal to the main roof
- The pitch of the tent roof (pitched roof surface with the same orientation and direction of rise as the main roof) is always less than the main roof pitch
- With a hipped roof, only one-sided hipped surface is possible
In order to ensure a homogeneous appearance, the same covering materials are usually used for the mid-roof as they are used for the main roof. Only if the pitch of the diaphragm is too shallow is sheet metal or foil used, if necessary as a contrast to the main roof.
The construction
As a rule, for reasons of economy, a mid-roof uses the roof structure used for the main roof. As the construction height, as already shown in the example, is often a problem, in-roof insulation with an insulation layer inserted between the rafters is often used. The inside vapor barrier and outside sub-roof membrane are connected to the corresponding levels of the main roof.
From a structural point of view, the loads from the diaphragm are transferred directly to the solid walls below. If, on the other hand, one does not consider a real transverse structure, but a dormer, the entire dormer, including walls and roof, is usually placed as a wooden structure on the rafters that border it. The wall structure is also based on the structure of the main and mid-roof and thus ultimately represents a kind of vertical part of the roof surface.
costs
Of course, every mid-roof means additional costs. Compared to the main roof, these are significantly higher for each cubic meter of volume created, as the envelope area is significantly higher. Small transverse structures to improve the usability of individual rooms can be realized for as little as 10,000 euros. If the transverse structure also emerges in the storeys below in front of the main structure, the costs increase accordingly.
Advantages and disadvantages
In most cases, these advantages and disadvantages have an impact on the diaphragm:
advantages
- Higher room height for better usability
- Additional vertical walls for better furnishing in the attic
- Better exposure options through the use of normal facade windows
- Design structure and loosening of the main roof
- Versatile in terms of dimensions, shape and roofing
disadvantage
- High costs in relation to the space created
- Very limited in size for small roofs
- Numerous constructive connection points on the main roof, therefore complex and prone to failure
- Only with a certain roof height or Inclination possible