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 innovate are making this unusual roof structure more and more widespread. Advantages and disadvantages are explained below, as well as general information about the barrel roof helps to understand its structure and the technical constraints.
The barrel roof
Originally, the barrel roof was mainly known from the area of sacred buildings, where brick barrel vaults denied 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 could be realized with a large span and at the same time almost any length, conquered the industrial and traffic engineering 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 structures and new, clear building shapes. Hardly to be found in postmodernism, the barrel roof is not experiencing a real renaissance today, worries but again and again for striking shapes and at the same time easily usable interiors for individually planned Residential houses.
Construction and statics of the barrel roof
Earlier barrel roofs were mostly created in the form of a classic, brick arched structure. This enabled the load to be transferred to the underlying, load-bearing outer walls via the arched surface made of stone or brick and mortar without any weak points. To absorb the outward pressure of the arch construction,
the walls were mostly stabilized towards the outside by additions or reinforcing transverse walls.Modern barrel roofs, on the other hand, generally correspond statically to what has developed in the course of industrialization and which has been used unchanged to this day in terms of load transfer. Static elements of the modern barrel roof are:
- Radially curved arches made of steel or wood
- Flat covering as a substrate for roof construction, mostly made of wooden boarding or sheet metal
- Bracing cross connections between the girders, often designed as a tension cross ("St. Andrew's Cross")
- Tension band between the lower support points of the arch support to absorb the shear forces at the arch base
NOTE: Not every single arch support has to be secured with a drawstring. In the case of short structures, the concrete ring anchors of the gable walls or a few tension straps that can be invisibly housed in the inner walls can be sufficient for this.
Roof structures on the barrel roof
Although the barrel roof is quite similar to the rafter roof in terms of the static structure of girders, it differs fundamentally in the structural structure of the roof. Due to the curvature of the roof surface, insulation between rafters and cladding of the soffit are possible, but usually extremely complex and therefore financially unprofitable. Instead, a roof structure for the barrel roof has established itself today:
Sandwich roof
- Arch beams visible in the interior
- Prefabricated sandwich element and adapted to the curvature of the girder, consisting of a lower supporting shell, insulation made of polystyrene and a top layer as weather protection and a water-bearing layer
- Top and bottom sheet metal, usually titanium zinc or aluminum
ATTENTION: Since these sandwich elements, which originally came from industrial construction, cannot be bent, the individual segments must be prefabricated to measure.
A barrel roof is made far less often as a wooden structure:
- Flat formwork as an inside visible covering on arched girders
- Vapor diffusion-tight layer on formwork, mostly foil
- Bearing timber running across the arch on formwork, insulated with mineral wool that can be flexibly adjusted to the curve of the roof
- Roof covering made of preformed sheet metal parts, if necessary on a substructure made of battens
NOTE: Since a classic counter-battens running from eaves to ridge is not an option for barrel roofs due to the curvature of the roof, sheet metal roofs that are not ventilated are mostly used here. Depending on the system used, the membrane preventing the entry of steam from the interior can then semi-overmeable, so that moisture in the insulation is nevertheless released to the inside can be.
Special forms of the barrel roof
For economic reasons, there are various shapes of barrel roofs that deviate from the real, continuously rounded arch:
Segment roof
- Dissolving the arc 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 in each case, therefore a high number of detail points
- Also suitable to a limited extent for tile roofing
"fake" barrel roof with ridge
- Formation of a ridge with arched roof surfaces on both sides
- Suitable for rear-ventilated constructions, as air can escape at the ridge point
- Mostly a slightly pointed shape deviating from a real bow
- Alternative roof coverings to the sheet metal possible, as the roof curvature is far less possible
Roof pitch or -rounding
The arched shape of the barrel roof results in the lack of a uniform roof pitch. Instead, each barrel roof always has a particularly steep one, regardless of the arc radius
Roof structures in the barrel roof
Dormer windows, transverse gables and roof balconies can be implemented equally well with the barrel roof. Transition points between the structure and the roof cladding can be resolved quite easily thanks to the common sheet metal covering. The steep incline at the foot of the full semicircular arc even makes it possible to use "normal" facade windows in the barrel roof to a certain extent. The usability of the roof space increases compared to others Roof shapes clearly.
costs
Due to a very limited selection of materials and a high degree of individually manufactured components, the barrel roof is an expensive roof shape. Although it also offers numerous advantages, none of them are to be found in the area of cost reduction and a high usability of series products "off the shelf". So you can see that the barrel roof is also clearly in the area of the individual in terms of costs planned individual building is to be relocated and is unlikely to appear in the creation of cheap living space should.
Advantages and disadvantages
As is clear from the preceding explanations, the rather unusual shape of the Barrel roofs have some elementary advantages, but with weaknesses that should not be neglected accompanied:
advantages
- Optimal ratio of envelope area to created space
- Due to the high incline at the barrel base, the rooms can be used well (almost vertical walls)
- Statically effective supporting structure due to the arch shape without a real field center
- With sheet metal roofing, no weak points in the form of transitions or ridge details
- Modern construction and design options
disadvantage
- No classic constructive structure can be implemented
- Economical structure limited to steel or wood, but wood is quite expensive due to the cost of manufacturing the arch girders
- Limited selection of possible roof coverings
- Great effort and precise planning required for the prefabrication of the roof elements
- high costs