The gable roof has been found in a wide variety of cultural regions and on a wide variety of building typologies for thousands of years. This already historically established and at the same time versatile use is no coincidence. Because the saddle roof impresses with its enormous flexibility and changeability. Everything you need to know about this archetype of a roof, which is still brand new today, can be found here.
The origin of the gable roof
The origin of the gable roof is unclear and is lost in prehistoric phases. Presumably it arose in numerous cultures, or rather in precultural phases, independently of one another. Why this is so can be easily explained by means of its simplest construction forms. If you lean two poles, branches or other load-bearing elements against each other, you already have a segment of a gable roof. Covered with a dense material, it offers an astonishingly large amount of space in relation to the effort and at the same time ensures safe drainage of rainwater. Of course, materials and dimensions have changed significantly in the course of history, but the basic functional principles have remained unchanged to this day. It is therefore easy to understand that this effective and economical roof shape can still be found on the majority of the buildings erected today.
Construction and statics
From a structural point of view, the modern saddle roof has two systems to make the structure stable erect and meet all requirements for interior space, load-bearing capacity and structure of thermal insulation and sealing raising.
The rafter roof
The rafter roof is still very close to the shape of two support elements leaning against one another, which was already described in the context of the creation. Because with the rafter roof, the opposite rafters are supported and form together with the underlying supporting element, i.e. ceiling or wall, is a self-stiffening and supporting one Triangle. Lined up one behind the other in almost any number, these load-bearing triangles result in a gable roof. The number of statically required elements is manageable with this type of gable roof:
-
Threshold:
forms the lower support of the rafters and at the same time the transition point between the underlying walls or ceilings and the roof structure -
Rafters
load-bearing elements, each in pairs in an opposing arrangement -
Stiffening
Required in the longitudinal direction of the ridge, today mostly as diagonal wind stripes or as a statically effective, flat sub-roof
NOTE: From a static point of view, a ridge is not required for the rafter roof. In order to be able to design the building envelope in a structurally clean manner at this upper joint of the roof surfaces, a ridge beam or a vertical ridge plank is usually formed. This carries, for example, the ridge tile on the tiled roof, or the ridge sheet on foil, sheet metal or green roofs.
The purlin roof
Compared to the rafter roof, the purlin roof appears to be more elaborate in its construction, due to the fact that it is still present Simplicity and adaptability but still clearly structured and simple in comparison to numerous others Roof shapes. Here, too, the rafters form the core element of the structure. However, they no longer support each other, but only carry the loads from the roof surface onto the supporting structure. The loads are carried over at least two, but mostly three load-bearing points per rafter: threshold or purlin, central purlin and ridge. The overview of the statically effective elements is therefore similar, but slightly longer, than for the rafter roof:
-
threshold
Base of the rafters and connection to the building below -
Middle purlin
Medium support and load transfer required for large rafters, either on a wooden structure or on solid interior walls in the attic -
First
Upper support and load transfer point of the rafters, usually placed on gable walls and supports or interior walls positioned in between
NOTE: From a static point of view, the use of a central purlin transforms the rafter from a single-span beam placed on two points into a multi-span beam placed on three points. In this case, not only is the load distributed over several support points, the deflection of the individual fields is also reduced due to the involvement of the neighboring field. With a central purlin, a rafter can therefore be significantly reduced in the statically required cross-section and overall, even less material is required than without a central purlin!
The waterproofing
In addition to stability, a roof has always had to offer weather protection. Today, in addition to impermeability to rain, this also includes impermeability to wind and water vapor, which penetrates into the construction from the room air and leads to moisture and mold damage can. A gable roof therefore typically consists of two sealing levels:
1. Inner
seal- Task: Diffusion tightness from the inside to the outside, as well as airtight level
- Usually applied to the inside of the rafter layer
- Must be installed within the main insulation package
2. External seal
- Task: Waterproofing against rainwater
- Created outside of the insulation layers
- Can be combined with insulation (e.g. B. Soft wood fiber board) or roofing (e.g. B. Sheet metal or foil roof), or as a separate level (e.g. B. Tiled roof)
- If the roofing is not completely tight (e.g. B. Brick) required as a water-draining layer if rain or snow is pressed under the brick by the wind
The thermal insulation
Independent of Roof shape the topic of thermal insulation plays an enormous role today. On the one hand, this results from the legal requirements and constantly rising energy prices. On the other hand, insulation is only necessary today, since loft spaces are usually the same Contain common rooms where previously, at most, unheated storage and storage rooms were provided.
The gable roof is very flexible and cooperative when it comes to thermal insulation: Most of the required insulation can be accommodated between the load-bearing rafters. Where the rafters are, there cannot logically be any insulation, only the insulation effect of most of them The wood used for the rafters is sufficient to achieve adequate insulation performance. This insulation package can be supplemented with insulation layers on the rafters or even on the underside. Common insulation materials are these:
For insulation between rafters:
- Mineral wool (formerly glass wool, today rock wool)
- Cellulose insulation
- Ecologically sensible insulation materials, such as sheep's wool, hemp, etc.
- Soft wood fiber boards
NOTE: The use of dimensionally stable, non-flexible insulation between the rafters would be possible, but the Joints caused by shrinkage and movement of the wooden rafters lead to a considerable reduction in the insulation effect to lead.
For above and below rafter insulation:
- Soft insulation materials such as insulation between the rafters, then timber for roof construction or inside cladding required
- Plastic foams as dimensionally stable insulating layers on which roof coverings can be applied without a structural supporting structure
- Dimensionally stable and pressure-resistant soft wood fiber boards
The advantage of insulation between the rafters is that the roof structure is very small. If, on the other hand, the rafters are to remain visible, the entire insulation can also be placed on the supporting structure. Depending on the insulation material, it may then be necessary to create a load-bearing level in the form of wooden formwork on which the insulation layer rests.
Roofing
A gable roof can be created with almost all common roof coverings that the market offers today. But traditional building materials can still be used, taking modern requirements for tightness and thermal insulation into account:
- Historic thatch, straw and reed coverings
- Bricks and concrete roof tiles
- Sheet metal (aluminum, copper, titanium zinc etc.)
- Foil roofs, graveled or greened on flat slopes
Modern special forms of roofing can sometimes even combine load-bearing, insulating and sealing aspects. For example, if a sandwich element is used as the roofing, there are of course no load-bearing elements underneath Elements such as rafters, as the element panels are self-supporting between the ridge, central purlin and threshold can. There is also no need for insulation or sealing.
The roof pitch
The classic gable roof shape is symmetrical and has the same inclination on both roof surfaces. Possible inclinations depend on the roof shape used and are also subject to fluctuations depending on fashion and
Use of the roof space.Slopes depending on the roofing:
-
Brick and Concrete:
depending on the brick up to 15 °, some models even 10 ° possible -
Foil:
theoretically 0 ° possible, but at least 2 ° according to the flat roof guideline (then no longer a real saddle roof) -
sheet:
at least 5 ° -
Historical building materials:
no technical minimum specification according to DIN standard available, but mostly very steep slopes to rainwater before penetration into the material - often 45 ° and more, occasionally up to 60 or even 70 ° findable
The steeper the gable roof, the larger the usable roof space. However, as the roof height increases, there is also an ever larger roof peak, which itself can hardly be used again. Common roof pitches in modern residential construction are often between 25 and 35 °, although the roof is not directly on the ceiling, but on a piece of wall up to one meter high - the knee stick - rests. For design or urban planning reasons, however, roofs with higher or lower inclinations are still regularly used.
Incidentally, special requirements or local conditions can always mean that a gable roof is not built symmetrically. For example, on a hillside, the roof surface on the mountain side can be made flatter in order to provide the wall below with a height that can be used for windows and doors.
Supplementary superstructures and installations
As simple as the gable roof itself appears, it can be expanded or changed in many ways. Numerous elements that can hardly be imagined away from the roof landscape today expand or improve the usability of the rooms located in the roof space.
The origin of all changes
Regardless of which element is inserted into a gable roof, it always involves intervention in the load-bearing rafters. Most of the time, parts of one or more rafters have to be removed. In order to maintain the load-bearing capacity, a so-called change is then inserted. Interchangeable pieces of wood running across the rafters catch the trimmed rafters and divert its loads into the neighboring rafters.
Skylight
- Make lounges in the roof possible through exposure and ventilation
- Offer additional space by eliminating the rafter and insulation package under the window area
- Today it is even available floor-to-ceiling and can be exhibited as a miniature balcony
- Common forms of top-hung, top-hung or top-hung windows
Roof balconies
- Either from the roof area or as a loggia in the attic possible
- Very intimate, hard-to-see outside area, as the roof areas provide good privacy
Dormers
- Create additional headroom in the attic
- Create vertical, easily furnished walls instead of sloping ceilings
- Versatile design possible, e.g. B. Gable roof dormer, barbed dormer, Flat roofdormer etc.
- Very good exposure through the use of normal facade windows instead of skylights
Advantages and disadvantages
A gable roof has many advantages, the downside of which is one or the other disadvantage. These are always recurring:
advantages
- Simple construction
- Inexpensive to erect due to the simple structure and efficient use of materials
- Versatile in design
- Thanks to numerous additions, it can be easily expanded and changed
- Good water drainage due to the inclination of the roof surfaces, thus less susceptible to damage in the event of structural weaknesses
- Interior can be easily adapted to use by adjusting the roof pitch
disadvantage
- Sloping ceilings difficult to furnish
- In the case of supplementary elements, comparatively high expenditure for connections and transitions
- With a steep incline, the roof tip is hardly usable
