Gable roof from A-Z: Information about the structure, advantages and disadvantages and inclination

The gabled 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 gable roof impresses with its enormous flexibility and changeability. Everything worth knowing about this archetype of a roof, which is still very relevant today, can be found here.

The Origin of the Gable Roof

The origin of the gable roof is unclear and is already lost in prehistoric phases. It probably arose in numerous cultures, or rather pre-cultural phases, independently of each other. Why this is so can be explained very easily on the basis of its simplest construction forms. If you lean two poles, branches or other supporting elements against each other, you already have a segment of a gabled roof. Covered with a dense material, it offers a surprising amount of space in relation to the effort and at the same time ensures that rainwater is safely drained away. Of course, materials and dimensions have changed significantly over the course of history, but the basic functional principles have remained unchanged to this day. So it is easy to understand that this effective and economical roof shape can still be found on the vast majority of buildings constructed today.

construction and statics

From a structural point of view, there are two systems for the modern gabled roof to ensure the construction is stable erect and meet all requirements for the interior, load-bearing capacity and structure of the thermal insulation and sealing raise.

The rafter roof

The rafter roof is still very close to the shape of two supporting elements leaning against each other, which was already described in the context of the creation. Because with the rafter roof, the opposite rafters support each other and form together with the the load-bearing element underneath, i.e. ceiling or wall, is a self-bracing and self-supporting one Triangle. Arranged in almost any number in a row, these load-bearing triangles result in a gabled 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 construction
• rafters
  supporting elements, each in pairs in an opposing arrangement
• bracing
  required in the longitudinal direction of the ridge, today mostly as diagonal windbreak strips, or as a statically effective, flat sub-roof

The purlin roof

Compared to the rafter roof, the purlin roof appears more complex in its construction, due to the still existing Simplicity and adaptability but still clearly structured and simple compared 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 of the roof surface onto the supporting structure. The loads are carried by at least two, but usually three, load-bearing points per rafter: sill or toe purlin, middle purlin and ridge. The overview of the statically effective elements is therefore similar, but somewhat longer, than with the rafter roof:

• threshold
  Base of the rafter system and connection to the building below
• central 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

The waterproofing

In addition to stability, a roof has always had to offer weather protection. Today, in addition to being impervious to rain, this also includes impermeability to wind and water vapour, which penetrates into the construction from the indoor air and leads to moisture and mold damage can. A gable roof therefore traditionally consists of two sealing levels:

1. Inner sealing

• Task: Diffusion tightness from inside to outside, as well as airtight level
• Usually applied on the inside of the rafter system
• Must be included within the main insulation package

2. Outer waterproofing

• Task: Waterproofing against rainwater
• Created outside the insulation layers
• Can be combined with insulation (e.g. B. soft wood fiber board) or roof covering (e.g. B. sheet metal or foil roof), or as a separate level (e.g. B. tiled roof)
• If the roofing is not completely sealed (e.g. B. bricks) as a drainage layer when rain or snow is forced under the bricks 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, the insulation is only necessary today because attic rooms are usually too Contain living rooms where at most unheated storage and storage rooms were previously 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. Logically, there can be no insulation where the rafters are, only the insulating effect of the mostly However, the wood used for the rafters is sufficient to achieve adequate insulation performance. This insulation package can be supplemented with insulation layers on the rafter layer or even on its underside. Common insulating materials are these:

For between-rafter insulation:

• mineral wool (formerly glass wool, now rock wool)
• cellulose insulation
• Ecologically sensible insulating materials such as sheep's wool, hemp, etc.
• softwood fiber boards

For above and below rafter insulation:

• Soft insulating materials such as insulation between rafters, then joists for roof construction or interior paneling required
• Plastic foams as dimensionally stable insulation layers on which roof coverings can be applied without a constructive supporting structure
• Dimensionally stable and pressure-resistant soft wood fiber panels

The advantage of insulation between the rafters lies in the relatively small roof structure. 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 insulating material, it may then be necessary to create a load-bearing level in the form of wooden formwork on which the insulating layer rests.

roof coverings

A gable roof can be created with almost all common roof coverings that are available on the market today. However, traditional building materials can still be used if modern requirements for tightness and thermal insulation are taken into account:

• Historical thatched, straw and reed coverings
• Bricks and concrete roof tiles
• Sheet metal (aluminium, copper, titanium zinc etc.)
• Foil roofs, gravelled or planted with flat slopes

Modern special forms of roofing can sometimes even combine load-bearing, insulating and sealing aspects. If, for example, 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, middle purlin and threshold can. Insulation and sealing are also omitted here.

The pitch of the roof

The classic pitched roof shape is symmetrical and has the same pitch on both roof surfaces. Possible inclinations depend on the roof shape used and are also subject to fluctuations depending on the fashion and use of the roof space.

Inclinations depending on the covering:

• Brick and concrete:
  depending on the tile up to 15°, some models even 10° possible
• Foil:
  0° theoretically possible, but at least 2° according to the flat roof guideline (then no longer a real gabled roof)
• sheet:
  at least 5°
• Historical building materials:
  There is no minimum technical specification according to the DIN standard, but mostly very steep inclines to avoid rainwater before penetrating the material - often 45° and more, occasionally up to 60 or even 70° discoverable

The steeper the gable roof, the larger the usable roof space. However, as the roof height increases, the peaked roof becomes larger and larger, which itself is hardly usable. Common roof pitches in modern residential construction are often between 25 and 35°, with the roof not directly on the ceiling, but on a piece of wall up to one meter high - the knee wall - rests. However, due to design or urban planning concerns, roofs with higher or lower pitches are still regularly used.

Incidentally, special requirements or local conditions can always lead to a gable roof not being built symmetrically. For example, on a hillside, the roof surface on the mountain side can be flatter in order to provide the wall below with a height that can be used for windows and doors.

Additional superstructures and installations

As simple as the gabled roof itself appears, it can be extended or changed in a variety of ways. Numerous elements that are now indispensable in the roof landscape expand or improve the usability of the rooms located in the attic.

The origin of all changes

Regardless of which element is inserted into a gable roof, this always involves intervention in the load-bearing rafters. In most cases, sections of one or more rafters have to be removed. In order to maintain the load-bearing capacity, a so-called change is then inserted. Alternating timber running transversely between the rafters catch the cut rafters and transfer its loads to the neighboring rafters.

skylight

• Enabling recreation rooms in the roof through lighting 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 displayed as a miniature balcony
• Common forms Top-hung, pivoting or top-hung and pivoting windows

rooftop balconies

• Either from the roof area, or as a loggia entering the roof space
• Very intimate, hard-to-see outdoor area, since good privacy is provided by the roof areas

dormers

• Create additional headroom in the attic
• Create vertical, easily furnished walls instead of sloping ceilings
• Possible in a variety of designs, e.g. B. Saddle roof dormer, trailing dormer, flat roofdormer etc.
• Very good exposure through the use of normal facade windows instead of skylights

Advantages and disadvantages

Now, a gable roof has many advantages, the downside of which is one or two disadvantages. These are recurring:

Advantages

• Simple construction
• Inexpensive to erect due to simple structure and efficient use of materials
• Versatile in design
• Easily expandable and changeable thanks to numerous additions
• Good water drainage due to the inclination of the roof surfaces, so less susceptible to damage in the event of structural weaknesses
• The interior can be easily adapted to use by adjusting the roof pitch

Disadvantages

• Difficult to furnish sloping ceilings
• Comparatively high effort for connections and transitions in the case of supplementary elements
• With a steep incline, the peak of the roof can hardly be used

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