Barrel roof information: structure and prices

The arched shape of the barrel roof can only be found on a few residential buildings in our latitudes. However, technical progress and the creative courage to try something new ensure that this unusual roof construction is becoming more widespread. Advantages and disadvantages are explained below, as well as general information about the barrel roof to help understand its structure and the technical constraints.

The barrel roof

Originally, the barrel roof was known mainly from the area of ​​sacred buildings, where brick barrel vaults first step from the flat ceiling to the filigree and at the same time highly complex structures of the Gothic marked. In the age of industrialization, this roof, which can be realized in a large span and at the same time in almost any length, conquered the industrial and transport building sector. It was only in the context of classical modernism in the 1920s that the barrel roof made its way into the world of residential buildings through the use of steel constructions and new, clear building shapes. Rarely to be found in postmodernism, the barrel roof is not experiencing a real renaissance today but again and again for distinctive forms and at the same time easily usable interiors with individually planned ones residential houses.

Construction and statics of the barrel roof

Earlier barrel roofs were usually created in the form of a classic, brick arch construction. This enabled the load to be transferred to the underlying, load-bearing outer walls via the curved surface made of stone or brick and mortar without any weak points. In order to absorb the pressure exerted by the arch construction to the outside, the walls were mostly stabilized on the outside by means of extensions or stiffening transverse walls.

In terms of statics, modern barrel roofs, on the other hand, usually correspond to what developed during the course of industrialization and is used unchanged to this day in terms of load transfer. Static elements of the modern barrel roof are:

• Radially curved arched girders made of steel or wood
• Flat covering as a base for roof construction, usually made of wood formwork or sheet metal
• Bracing cross connections between the girders, often designed as a cross brace ("Andreas Cross")
• Tension band between the lower support points of the arch girders to absorb the shearing forces at the arch attachment

Roof structures on barrel roofs

Although the barrel roof is quite similar to the rafter roof in terms of the structural structure of beams, it differs fundamentally in the structural design of the roof. Due to the curvature of the roof surface, insulation between the rafters and cladding of the bottom view are possible, but usually extremely complex and therefore not financially profitable. Instead, a roof structure for the barrel roof has established itself today:

sandwich roof

• Bow girder visible in the interior
• Prefabricated sandwich element and adapted to the curvature of the girder, consisting of a lower load-bearing shell, polystyrene insulation and a top layer as weather protection and water-bearing layer
• Top and bottom sheet metal, usually titanium zinc or aluminum

Far more rarely, a barrel roof is created as a wooden structure:

• Flat formwork as a covering visible from the inside on arched girders
• Vapor diffusion-tight level on formwork, mostly foil
• Crosswise to the vault running joists on formwork, insulated with mineral wool that can be flexibly adapted to the roof curve
• Roof covering made of preformed sheet metal parts, possibly on a substructure made of battens

Special forms of the barrel roof

For economic reasons, there are various forms of barrel roofs that deviate from the true, consistently rounded arch:

segment roof

• Resolution of the arch into a polygon with several straight sections
• Construction here like a straight roof surface is possible, but transition points between the roof segments are required, therefore a large number of detail points
• Conditionally also suitable for brick covering

"fake" barrel roof with ridge

• Formation of a ridge with curved roof surfaces on both sides
• Suitable for rear-ventilated constructions as air can escape at the ridge point
• Mostly slightly pointed shape deviating from real bow
• Conditionally alternative roof coverings to sheet metal are possible, since the roof curvature is much smaller

roof pitch or -rounding

The arched shape of the barrel roof results in the lack of a uniform roof pitch. Instead, every barrel roof, regardless of the arch radius, always has a particularly steep incline at the base and an almost non-existent incline at the apex. Not every barrel roof necessarily has to consist of a semicircle. Differently selected arch segments can lead from the well-known dome shape to a flat incline with an upward curve.

Roof structures in the barrel roof

Dormer windows, cross gables and roof balconies can be implemented equally well with barrel roofs. Due to the common covering with sheet metal, transition points between the structure and the roof skin can be solved quite easily. The fairly steep incline at the foot of the complete semicircular arch even makes it possible to use "normal" facade windows in the barrel roof to a certain extent. The usability of the roof space thus increases compared to others roof shapes clearly on.

Costs

Due to a very limited selection of materials and a large number of components to be individually manufactured, the barrel roof is considered an expensive roof shape. Although it also offers numerous advantages, none of these are to be found in the area of ​​cost reduction and a high degree of usability of "off-the-shelf" series products. So you can see that the barrel roof is also clearly in the area of ​​individual planned individual building and will hardly appear in the creation of affordable living space should.

Advantages and disadvantages

As is clear from the previous explanations, the rather unusual shape of the Barrel roof has some elementary advantages, albeit with weaknesses that should not be neglected accompanied:

Advantages

• Optimum ratio of envelope surface to created space
• Due to the high inclination at the foot of the barrel, good usability of the rooms (almost vertical walls)
• Statically effective supporting structure due to the arch shape without a real center of the span
• With sheet metal covering, no weak points in the form of transitions or ridge details
• Modern construction and design options

Disadvantages

• No classic structural design can be implemented
• Economical supporting structure limited to steel or wood, wood, however, is quite expensive due to the effort involved in manufacturing the arched girders
• Limited selection of possible roof coverings
• A lot of effort and precise planning required for the prefabrication of the roof elements
• high costs

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