Concrete roof tile

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Roof covering with colored concrete roof tiles (Harzer Pfanne)

Concrete roof tiles are artificially formed stones (so-called shaped stones ) and belong to the group of building materials and are primarily used to manufacture sloping roofs .

Concrete roof tiles are nowadays produced in industry by machine using an extrusion process from mineral aggregates and hydraulic binders . They usually consist of cement and sand containing quartz and are sealed on the outside by a cement slurry that is mixed with color and plastic pigments .

Differentiation from roof tiles

Roof tiles from concrete are colloquially called roof tiles , concrete tile or designated as lay the differences in products from clay not readily recognize, and sometimes it is not known that materials for roofing are made often made of clay, but of concrete. In professional circles, the term "roof tiles" is regularly used for products made of clay ("clay roof tiles"), while the term "roof stone" or "concrete roof tile" is common for products made of concrete.

A pile of concrete roof tiles, the surface coating is largely no longer present due to weathering. Moss is already growing in some roof tiles.
Weathered, partly moss-covered, old concrete roof tiles, after demolition.

Since the introduction of assembly line production, concrete roof tiles have long been considered to be significantly cheaper than clay roof tiles. For laypeople, the visual difference between clay roof tiles and concrete roof tiles when covered is increasingly difficult to see. This is due to the fact that the surfaces of the concrete roof tiles are becoming ever finer and tending to develop in the direction of the clay roof tiles, while the traditionally smaller-format clay roof tiles have also been available in larger formats for some years.

The weathering and patination behavior of concrete roof tiles and clay tiles is greatest, particularly in terms of color and visual appearance, with only superficially colored concrete roof tiles. In contrast to through-coloring, a layer of paint that has only been applied superficially can weather off after a few years, which means that the red color is lost. Over time, the appearance of an algae and lichen overgrown , non-colored concrete roof tile develops .

history

Manual production

Beginnings in Staudach - Adolph Kroher

The first concrete roof tiles were made around 1840 in Staudach , a small farming village in Upper Bavaria . The inventor is a young man named Adolph Kroher (May 3, 1825– April 23, 1892), who was a paper merchant in Augsburg and in 1858 had the Staudacher cement factory, which had been founded some time before, entered in the commercial register.

Around 1840, while on vacation in Grassau, near Staudach, Kroher met two part-time plaster manufacturers who mixed local mineral deposits and other materials in small quantities to plaster walls. He bought a farm and wooded land, which later became a quarry to remove the mineral deposits. Kroher produced the first diamond-shaped cement roof tiles in 1844 at the latest. He made use of workers who were not employed in winter and who processed the fast-setting Staudacher cement. The cement made it possible to take the stones out of their shape after a few hours. Kroher experimented with various shapes known from roof tiles and ultimately decided on diamond-shaped panels, which are also called "Dutch pans" in Bavaria. He found that with this shape, less moisture penetrated the joints of adjoining stones and they were less fragile than other shapes. They are also easier to carry to the roof and easy to misplace by halfway skilled men. Experiments with beaver tail shapes had shown that the weight of the cover was too great when double-layered.

The pans were made with so-called hand-held machines invented by Kroher. A jute sack lay on a wooden base plate so that the stones did not stick and could be removed more easily. On the stones produced up to 1870, the pattern of the sack fabric could be seen on the back. A steel ring of the same shape lay on a square block of wood. The steel ring opened like a pair of tongs. It could be moved upwards with a hinge to insert shims. On the side opposite the hinge it could be held together with a clamping device, but it could also be pressed onto the base plate.

The mortar was hammered into the steel ring, rubbed in and smoothed before the steel ring was clamped out, pulled apart and folded over backwards so that the base plate with the roofing stone produced in this way could be removed.

In addition to his own production of the roof tiles, Kroher created do-it-yourself instructions early on , which non-specialists could use together with cement and hand hammer machines supplied by him to produce roof tiles themselves. The quality of the roof tiles thus varied depending on the knowledge of the user and the use of other aggregates if necessary.

Kroher himself manufactured concrete roof tiles by constantly adding only a few clean, sharp, twice-sieved sand from the Tiroler Ache to the Staudacher cement that he sieved .

As early as 1873, 120 men were involved in the production, but also the structural use of the products, half of them came from Italy. This year Kroher received a recognition diploma for his roof tiles. The daily output should have been around 125 pieces per worker. The concrete roof tiles were used, among other things, for a major order from the Austrian government , which had all the roofs of train stations , signal stations, workers' houses, etc. along the Tauern Railway , which was newly built at the time , covered with it. In 1959 the author Dobson (History of the Concrete Roofing Stone) stated that most of these buildings were now covered with asbestos cement . In 1865 Kroher produced roof tiles with side seams for the first time in order to achieve better protection against rainwater. At an exhibition in Arnhem (Netherlands) in 1879, roofing tiles that were 35 years old were shown, which showed no signs of weathering or permeability and which are said to have been stronger than newly manufactured tiles. From this it can be roughly concluded when production began at the latest. The Staudacher production is considered to be the world's first manufacture of concrete roof tiles.

In 1929 the Kroher family stopped manufacturing concrete products and sold the cement factories. She justified this with the German inflation , but also with the unprofitability compared to the machine-made single-fold clay bricks since 1840. Roof tiles produced by Kroher in the middle of the 19th century and laid on his house still served their purpose 100 years later.

Concrete roof tile production in Guben

Around 1883 the production of "cement roof tiles" began in Guben ( Niederlausitz , southeast of Berlin ), which in 1907 was one of the centers of concrete roof tile production .

Concrete roof tiles in the north - Haseldorf, Quickborn and Wedel

The Dane JP Jörgensen (1852–1933), who came to Haseldorf in Schleswig-Holstein in 1871 to build a mausoleum , registered his first patent in 1882 for "Innovations in roof interlocking tiles made of cement", which was registered under number 20772 by the Royal Patent Office on June 23, 1882 was issued. It was about a foundation stone and a capstone. They were very similar to the Broomhall clay tiles made in Bridgewater, patented in England in 1805 and 1855 by William Wilkinson and Thomas Taylor Coniam, respectively. There is no known evidence of the relationship between the models.

He built his first factory in Wedel in 1883 . There he received his first patent "Innovations in roof interlocking tiles made of cement". In 1902 he sold the factory, which was destroyed by fire or explosion in 1907. In 1895 he built a second factory in Quickborn , which he sold in 1925 to G. Rademacher, who himself was active in the branch on the opposite side of the street. Rademacher's Cementziegelei und Cementwaren-Fabrik announced in 1901 that “after careful deliberation and after consulting with the authorities,” he had decided to manufacture diamond-shaped concrete roof tiles. Before founding his cement roof tile factory, he had dealt with the matter and reports from authorities in the construction industry for a long time. It is the multiple patented “Reisings saddle interlocking tile with double rebate”, “The roof of the future.”, “Without mortar coating”. The bricks had a double fold on the top and bottom and a hook on top on the bottom. There were also "half" and ridge tiles. The diamond-shaped roof stone was made on a machine patented by Reising, which is similar to that of Kröher, with the form being mounted on a table with pedals . The patent was granted for an improved shape of the fold.

Other early centers for the manufacture of concrete roof tiles

Also Roding , Bad Reichenhall and Oberkassel (Hüser Betonsteinwerke) are known as early centers of production of concrete roof tiles. Hartwig Hüser founded a company as early as 1850, registered a patent for diamond-shaped concrete roof panels in 1878 and produced them from Rhine sand and Portland cement . After the Second World War , the machines were sold and production stopped. The production of concrete roof tiles is also known from the Middle Franconian Schallfeld .

Ludwig Nicol from Munich was employed by Reisig and on October 21, 1899, registered a patent number 115074 for a machine that could be used to produce diamond-shaped roof and floor panels, similar to the saddle interlocking tiles advertised by Rademacher. A Reisig patent with number 103522, dated August 3, 1895, gives reason to assume that on the one hand he proposed to the Reisig and Sons company that their press be rebuilt in 1898 so that floor panels could also be produced with it, and on the other, Reisig was involved helped and contributed to registering the patent.

Heinrich Ritter, Hoffenheim concrete roof tile factory

The concrete roof tile factory Heinrich Ritter in Hoffenheim announced on 7 August 1951, a patent (DE000001631179U) for verge -Betondachsteine to, characterized by ridges on both sides that carry either the left or right at the bottom of an end plate to use them for the first time right and left to can as well as a device intended for this purpose for the production with two base plates, which screws by wing o. Ä. Are connected. Heinrich Ritter stated that he had been producing concrete roof tiles for around 15 years (i.e. since 1936). There is talk of a “knight” model.

The way of the concrete roof tiles to England

The concrete roof tile is said to have come to England around 1895 . The roof tiles were made there on German machines. In Devonshire (now the county of Devon in south-west England) in 1898 all station buildings on a light rail line were covered with concrete roof tiles. RH Baumgarten, who came from Neuruppin , called his production "cement tiles" and his products as the "roof of the future" before he moved to England in 1905. Concrete roof tiles were subsequently able to establish themselves as the preferred roofing material. In 1936, a single English company is said to have manufactured 203 million roof tiles per year and provided them with a fifty-year guarantee.

Assembly line production

Beginnings in Germany by Rudolf H. Braas in Köppern with the "Köpperner Dachplatte"

Following the English model, assembly line production was introduced in 1954 for the manufacture of concrete roof tiles . This development was associated with the name Rudolf H. Braas . As the owner of a hard stone company in Austria ( Carinthia ), he got to know the manual production of roof tiles with hand cutting tables. Between 1945 and 1948 Braas developed a roof tile machine with two belts running next to one another and produced the "Köpperner roof tile", a flat, plate-shaped roof tile (similar to today's Tegalit model).

On October 2nd, 1948, the inventor Braas from Köppern (Taunus) registered a machine for the production of concrete roof tiles. At that time, the need for roof tiles was estimated at around 6-7 billion pieces. The grant of the patent was announced on February 1, 1951 under reference number HAIHO Pat. No. 803468. The machine was created together with a locksmith's shop in Anspach. You should for automatic, continuous production of concrete roof tiles on a rotating chain belt (mold chain) and have numerous in-chain forms, as well as feed, pressing and auxiliary devices that the necessary operations running and smooth continuous operation and quality are beneficial the product.

Braas also describes the process that has been observed so far in his patent application. The production takes place almost exclusively by hand, by placing a profile plate in a mold frame, applying the concrete mixture to this plate and compacting the mixture by knocking or tamping it by hand. The imperfection of the quantity that can be produced and the uniformity of the products are evident in this process. With mechanically driven shaking or vibration tables with a large number of molds, the compaction of the mass has already been carried out. When using a relatively liquid concrete mix, a reasonably satisfactory level of compaction can be achieved, but the cement utilization is unfavorable. In order to increase the quantity, it has already been proposed to apply molds to links of a revolving chain, which then pass under a filling device that fills them by automatic opening and closing and then passes under a profile roller. However, the process is not free from defects, the concrete mass is not sufficiently compacted in the mold and the mass production is undesirably interrupted by the interruptions in the delivery of the concrete mixture into the molds. In addition, a considerable number of shapes are required.

Braas intended to avoid the disadvantages and manufacture up to 1,000 concrete roof tiles per hour with a low labor force. The Braas machine had a revolving chain that carried the shapes. The chain links are rectangular grids and form the shapes of the stones. The grids merge into upright frame strips on the long sides, which form the shaped edges. A loosely removable base plate is inserted in these rectangular grids. The molds should be connected to each other by chain link pins and directly adjoin each other so that the concrete mix can run into the molds without interruption. A precompacting device, an automatic compacting press, a smoothing device, a concrete cutting machine and an automatic lifting device should be arranged above or below the horizontally running chain section. A device feeding a paper tape is arranged in front of the concrete filler. The lower part of the chain lies in a liquid bath. The cutting machine consists of a spring-loaded drop knife that acts when triggered . The lifting device consists of lifting bodies which are guided on an inclined plane and attached to the chain links. The lifting bodies grip the loose base plates and lift them up. The method for producing the concrete roof tiles is characterized in that they are cut into pieces from a continuous concrete strip. The concrete roof is continuously pre-compacted, then finally pressed, smoothed and cut.

In 1950 Braas visited English Dachstein companies on a two-week trip. In Bad Homburg vor der Höhe he initiated a “concrete roof tiles working group” and reported there on February 20, deeply impressed by the state of development there, which was decades ahead of the German. As a consequence, he modernized his systems. On January 20, 1952, he received approval from the Hessian Minister of the Interior for the new Köpperner roof panel . Th. Aulmann, Chairman of the Central Association of the German Roofing Trade , gave the Köpperner roof panels his highest appreciation.

In 1953 the so-called extrusion process by the English engineer Harold Carter was put into operation. At first 40 concrete roof tiles were produced per minute. Cement was added by hand in sacks, and sand was added using simple scales. Form stones (ridges, verges, etc.) were still made on hand-held tables. In 1954 the production of the roof tiles in Köppern was stopped and the families Braas, Dressel and the British company Redland Tiles Ltd. continued in Heusenstamm under the “Frankfurter Pfanne” brand. In 2008 there were still two houses and a garden hut in Köppern, the roofs of which were completely covered with the Köppern roof plate.

At the same time, the Finkenberger pan came onto the market in 1954 by the Nelskamp company.

Sales development from the 1960s

Production and sales in the concrete roof tile industry recorded an upward trend due to assembly line production , which was reinforced by a trend away from smaller formats (15–16 stones per m²) to concrete roof tiles as double-sided roof tiles with larger formats (9.5–10 stones per m²). In addition, the roof weights of these larger-format concrete roof tiles, depending on the roof pitch and the resulting vertical cover, were 42–48 kg per m², lower than for clay roof tiles. The signs of a recession in the construction market in 1966 and 1967 did not slow down the upswing in concrete roof tiles. As in England after the end of World War II, more concrete roof tiles were produced in Germany than clay roof tiles in 1968. The proportion of concrete roof tiles was around 68% in 1973, the proportion of clay roof tiles only 32% (ratio 1960: concrete roof tiles = 12%; clay roof tiles = 88%). A slowdown only became apparent in 1974.

Market since the 1980s

In 1981 the Heidelberg Dachstein came onto the market through the company Eternit. In the 1980s, the Braas Group had an outstanding position in the concrete roof tile market segment it had developed , with a market share of over 80% . The share of concrete roof tiles in the overall market had been declining for years. Instead, after its low point at the beginning of the 1970s, the clay roof tile was able to increase its market share in the pitched roof market from 10% to approx. 45% in 1999 within 25 years .

Market in 1999

The Federal Cartel Office presented as part of a test of a proposed concentration fixed for the year 1999, a division of the market of small-format roofing materials for pitched roofs m² in value terms total market volume of about 3.2 billion DM and a volume terms total volume of 116 million, which was attributable to:

  • Concrete roof tiles approx. 45% proportion (value approx. 1,133 million DM = approx. 35.7%),
  • Clay roof tiles approx. 45% proportion (value approx. 1,513 million DM = approx. 47.7%),
  • Fiber cement boards , slate and other small formats approx. 10% proportion (value approx. 529 million DM = approx. 16.6%).

The reason for the gains in clay roof tiles was based in particular on significant price reductions and improvements in quality and ease of installation. According to industry surveys , the tendency for clay roof tiles continued to rise, for concrete roof tiles it continued to decline, as the demand should come mainly from the areas of single-family house construction and renovation as well as monument preservation . In multi-family house construction , the focus of sales for concrete roof tiles, a decline was expected. With the Harzer Pfanne BIG, Braas launched the first roof tile on the market in 1999, of which, depending on the roof pitch, only 7.5–8.2 pieces per m² are required and which, despite an increase in size of almost 25%, is hardly heavier than conventional roof tiles .

Manufacturer - based in Germany

There are four major manufacturers of concrete roof tiles in Germany:

For many years Braas (formerly Braas Dachsysteme GmbH or Lafarge Dachsysteme and most recently Monier Braas) was the market leader in concrete roof tiles in Germany. The value share of the then Braas Dachsysteme GmbH was> 60% in 1999. According to the Federal Cartel Office, Braas thus had a very prominent position.

Current Dachstein shapes and models in comparison (July 2012)

Characteristics of the Dachstein forms Benders
(requirement per m²)		 Braas
(requirement per m²)		 Creaton
(requirement per m²)		 Nelskamp
(requirement per m²)
straight, small symmetrical central bulge Mecklenburg
burgers (9.7-10.6 pieces)		 Frankfurter pan
(approx. 9.7-10.7 pieces)		 Heidelberg
(approx. 9.7-10.7 pieces)		 Finkenberger pan
(approx. 10 pieces)
curved, symmetrical central bulge Palema S
(9.7-10.6 pieces)		 Harzer pan
(approx. 9.7-10.7 pieces)

Harzer pan 7 (BIG)
(approx. 7.5-8.2 pieces)

Harzer pan F + (BRAAS 7GRAD DACH)
(8.2 pieces)		 --- Sigma pan
(approx. 10 pieces)
curved, asymmetrical central bulge --- Double S
(approx. 9.7-10.7 pieces)		 Gothenburg
(approx. 9.7-10.7 pieces)		 S-pan
(approx. 10 pieces)
flat, plate-shaped Carisma
(11.6-12.7 pieces)		 Tegalite
(approx. 9.8-10.7 pieces)		 Cape Town
(approx. 9.7-10.7 pieces)		 Planum (10 pieces)
straight, large symmetrical central bulge --- Taunus pan
(approx. 9.7-10.7 pieces)		 --- Crown pan
(approx. 10 pieces)
curved, trough-shaped Single-S
(11.6-12.7 pieces)		 --- Verona
(approx. 9.7-10.7 pieces)		 ---

Source: Internet pages of the manufacturer, accessed on July 14, 2012.

Accessories for concrete roof tiles

In addition to the normal stones used mainly in the roof areas, depending on the manufacturer and model, other concrete shaped stones are usually available as accessories for special functions, e.g. B .:

  • Special covering width (half normal stones, jumbo stone)
  • Ridge and ridge (ridge stones, ridge end stones, ridge starting stones, hip caps )
  • Gable and verge (gable or verge stones, keystones)
  • Roof tiles for the roof kink (whole and half kink stones, whole or half mansard stones , mansard gable or verge stones , kink gable or verge stones)
  • Shed roofs (whole or half shed stones, shed gable or verge stone)
  • Standing / functional stones (for walkways, steps, safety steps, steps, gratings, roof hooks, snow guard systems)
  • Ventilation etc. (fan stone, bat stone)
  • Roof decorations (ridge discs, ridge taps, sleepwalkers, ridge cats)

Source: Internet pages of the manufacturer, accessed on July 14, 2012.

DIN standards for concrete roof tiles

The emergence of a DIN standard for concrete roof tiles is known as early as 1950 . today DIN EN 490, DIN EN 491 and DINplus are used.

DIN EN 490

In DIN EN 490: 2012-01 “Roof and shaped stones made of concrete for roofs and wall cladding - product requirements; German version EN 490: 2011 “specifies the current requirements for roof and shaped stones made of concrete for pitched roofs and for interior and exterior wall cladding. The roof and shaped stones made of concrete can have a surface coating. They can consist of concrete components glued together. Compared to DIN EN 490: 2006-09, the requirements for fire protection have been changed and editorial revisions have been made.

In addition to the area of ​​application, normative references, terms, symbols and abbreviations, the standard specifies the product requirements for concrete roof tiles, in particular for the following areas:

  • Fabrics
  • Dimensions (hanging length and squareness, covering width, evenness, shaped stones)
  • Dimensions
  • Mounting holes (if any)
  • Mechanical strength ( load capacity )
  • Impermeability to water
  • Durability (freeze-thaw alternation resistance for roof, shaped and valley stones)
  • Hanging noses
  • Behavior in the event of fire
  • Release of dangerous substances

In addition, there are notes on conformity assessment , sampling , the labeling system , marking and labeling and other documents .

DIN EN 491

In DIN EN 491: 2011-11 “Roof and shaped stones made of concrete for roofs and wall cladding - test methods ; German version EN 491: 2011 "test methods for roof tiles and shaped stones made of concrete according to EN 490 for installation in sloping roofs or exterior and interior wall cladding are specified. Compared to DIN EN 491: 2005-03 and DIN EN 491 Correction 1: 2007-05, the requirements for fire protection have been changed and editorial revisions have been made.

In addition to the area of ​​application, normative references , terms, symbols and abbreviations, the standard specifies the framework conditions for test methods for concrete roof tiles, in particular for the following areas:

DINplus

In addition to the minimum requirements of the European standards DIN 490/491, which has existed since 1994, on strength , water impermeability, frost resistance, etc., some concrete roof tiles now meet further requirements, including quality features not only relating to the nature of the product, but also to practical application:

Technical details and their effects on use

Roof coverings with concrete roof tiles are single-layered or with a substructure. A ventilation opening is always required. Concrete roof tiles are usually larger than clay roof tiles. The larger the formats, the fewer joints the roofs contain and the faster they need to be covered.

The fold

In contrast to many clay roof tiles, the horizontal folds ( rabbet tiles ) are usually omitted with concrete roof tiles . The variable height overlap allows the coverage to be matched to the rafter length . In the case of profiled concrete roof tiles (e.g. Finkenberger Pfanne, Frankfurter Pfanne), the longitudinal rebate is carried out rather high, while it is carried out low on non-profiled roof tiles (e.g. Tegalit).

Effects on the minimum roof pitch

If concrete roof tiles with a high rebate are used without a substructure, the incline of the roof must be at least 22 °, with a deep rebate the minimum incline increases to 25 °. If the roof is constructed with substructures, the minimum roof pitch for concrete roof tiles with a high rebate can be reduced to up to 16%. Such substructures can consist of additional measures such as laying an underlay or a sub- roof , e.g. B. as wooden formwork with a barrier layer of bitumen roofing membranes .

Effects on the minimum height coverage

The minimum height coverage also depends on the rebate of the concrete roof tiles used and the respective roof pitch. The minimum overlap with a high rebate is only 7.5 cm with a roof pitch of more than 30 °; at 22–30 °, 8.5 cm is required. If the rebate is deep, at least 8 cm is required, which, however, requires a roof pitch of more than 35 °; if it is only 25–35 °, 9.5 cm must be observed; at less than 25 ° a minimum overlap of 10.5 cm is required.

Patents in the field of concrete roof tiles

Auxiliary rib at the foot end to protect the sealing strip

In 1963, the Nelskamp roof tile works had a concrete roof tile for a non-foldable roof covering protected with utility model DE000001807203U. Concrete roof tiles had only one side rabbet, at the head end a transverse hanging bar and at the foot end a transverse rib with which the stone rests on the stone below. Since these stones would not result in a sufficiently tight roof covering without head rabbet, it is necessary to put a sealing strip on top of the foot rib, e.g. B. foam rubber , glass wool , jute etc. insert. The strip could be brought out of its position or blown out by the effects of wind, so that the sealing effect would be lost. With the patent, a second, somewhat lower auxiliary rib resting on the covered stone was therefore provided parallel to it on the upper side of the foot rib in order to be able to put the strip in the space between the two ribs in a protected manner.

Second cross rib at the foot end to protect the sealing strip

The roof tiles Nelskamp settled in 1963 with patent DE000001125629A protect a concrete roof tile for a querfalzlose roofing, similar to that in 1959 registered design .

Auxiliary rib on the ridge side on the top to protect the sealing strip

In 1959, the roof tile works Nelskamp had a concrete roof tile for a roof covering without cross folds protected with patent DE000001806721U. Concrete roof tiles had only one side rabbet, at the head end a transverse hanging bar and at the foot end a transverse rib with which the stone rests on the stone below. Since these stones would not result in a sufficiently tight roof covering without head rabbet, it is necessary to put a sealing strip on top of the foot rib, e.g. B. foam rubber, glass wool, jute etc. insert. The strip could be brought out of its position or blown out by the effects of wind, so that the sealing effect would be lost. With the patent, an auxiliary rib was provided on the upper side on the ridge side so that, together with the foot rib of the covering stone, a gap is created that protects the sealing strip from the effects of the wind.

Process for the production of a storm-proof concrete roof tile

Braas & Co. GmbH applied for patent DE000001924341U by letter of March 19, 1962. Previous concrete roof tiles could then be fastened with clamps that could be attached to the side or top of the stone and anchored to the roof structure . A disadvantage is the side tilting or the damaging moment exerted on the head side, which in connection with gusts of wind can lead to destruction of the stones and to leaks on the roofs. The invention provided that on the underside above the (two) foot / transverse ribs, additional formations / noses were to be attached in three places, which contain a plastic tube that could accommodate storm clips. In a second variant drawn in, three plastic tubes are embedded in a second foot / cross rib, once in the center of the inner area of ​​the central outer bead and once on both surfaces.

Concrete roof tiles with storm protection

Clay roof tiles have long been fitted with storm clips. In 1963, Nelskamp GmbH registered a patent with number DE000001884754U for concrete roof tiles that have an elevation or nose above the two foot / transverse ribs that has a through hole to accommodate storm clips . For this purpose, at the beginning of the compression process, a needle corresponding to the cross-section of the hole should be inserted into the body of the nose, which was withdrawn again when the compression was completed.

Longitudinal ribs between the foot / cross ribs to improve the flow behavior

Braas & Co., GmbH registered a patent with number DE000001609924B in 1966, in which several longitudinal ribs are provided, which, unlike the previously known longitudinal ribs running over the entire underside, only run between the two transverse foot ribs and not primarily for stabilization serve. Rather, they are intended to solve the problem that the rather narrow foot ribs have so far had relatively steep flank angles and small radii , which is why good compaction of the concrete was not possible and the transverse ribs crumbled. The additional longitudinal ribs between the transverse ribs should enable the transverse ribs to be properly formed, as they would lead to better flow conditions for the concrete during the compaction process.

Concrete roof tiles with a third rebate rib and groove in a wider side rebate

A side fold corresponding to at least two thirds of the cover bead was patented with the number DE000001977166U by Heinz Jürgen Kinzel from Kleestadt on July 28, 1967, which contains an additional third fold rib between the two existing fold ribs, which height the two lateral delimiting ribs running parallel to them towers. The two-ribbed designs up to now have been criticized for the fact that the ribs do not fully engage in the grooves of the neighboring stone, creating wide joints between the stones that allow rain, snow and dust to blow into the inside of the fold and thus into the roof interior.

Concrete roof tiles with a naturally rough surface; Problems with previous surfaces

With the file number DE3542369A1 04.06.1987 Braas & Co GmbH was granted a patent for a process for the production of concrete roof tiles with a naturally rough surface. The following surface finishing processes have become known for concrete roof tiles , which have proven to be insufficiently resistant in terms of their resistance over a desired long weathering period:

  • Leaving the cement extrusion skin so that the concrete roof tile had a relatively smooth surface; Consequence: weathering after 10–20 years.
  • The concrete roof tile surface is acidified after hot curing, preferably with 3-10% hydrochloric acid ; Consequence: reduced tendency to bloom , but undesirable change in the appearance of the concrete roof tile surface after 10-20 years.
  • A new slurry consisting of cement or sand and cement is subsequently applied to the concrete roof tile surface; The result: the initially shiny surface layer becomes matt, the entire layer of sludge weathers after approx. 10 years, with subsequent erosion as with concrete roof tiles with a cement extrusion skin.
  • Are applied to the concrete roof tile surface polymers ( acrylates , styrene acrylates , vinyl acetates etc.) or a slurry of clear lacquers , paints or gloss finishes, and the like applied. Consequence: the polymer coating is largely weathered after approx. 15 years; After complete removal, the erosion process follows as with concrete roof tiles with a cement extrusion skin.
  • Colored sand granulate (e.g. red sand granulate) is also applied to the slurry that has already been applied to the concrete roof tile surface; Consequence: the limited adhesive bond leads to its complete erosion, cement slurry becomes visible, the erosion sequence follows as with concrete roof tiles with a cement extrusion skin.

As a result, all concrete roof tile surfaces obtainable with these methods would have proven to be insufficiently resistant in terms of their resistance over a desired long weathering period.

Concrete roof tile produced in a strand process

Structures can be regularly formed in the strand process by sub-molding on the underside of the concrete roof tiles. If structures are to be formed on the upper side, the upper side must receive structure in the lower mold, so that the possibility of forming hanging lugs by lower molds is eliminated. The Eternit AG therefore settled on 15 June 1989, a utility model for particular produced in the strand method concrete roof tiles protect a Aufhängenase of plastic or other suitable material is inserted into the on the bottom at the top, in the pre-suspension lugs into the not yet cured Concrete mass are pressed.

Others

  • Concrete roof tiles can be supplemented by further system parts to form complete roof systems.
  • The largest concrete roof tile in the world measures 4.2 × 3.3 m, is modeled on the Frankfurt pan, weighs six tons and corresponds to the covered area of ​​approx. 140 roof tiles. It stands at the Braas site in Heusenstamm , can be viewed by the public and is entered in the Guinness Book of Records .
  • Compared to clay roof tiles, concrete roof tiles have a better ecological balance and are therefore preferable to them from an environmental point of view. Concrete roof tiles cause less than half of the climate-damaging carbon dioxide (CO 2 ) in the overall balance and score significantly better in almost all aspects examined. When it comes to atmospheric mercury emissions, roof tiles score 4 times less than clay roof tiles.

Web links

Individual evidence

  1. ^ FA Brockhaus 1996, 234.
  2. ^ A b Michael Stahr, Dietrich Hinz: Renovation and expansion of roofs: Fundamentals - materials - execution . 2011, p. 306.
  3. ^ Judgment of the VGH Kassel of April 2nd, 1992, file number: 3 N 2241/89, margin no. 26. Hessischer Verwaltungsgerichtshof Kassel, accessed on July 14, 2012 .
  4. ↑ History of the concrete roof stone, Charles G. Dobson, 1959, 19.
  5. ↑ Alex Welte: Company history of the Staudacher cement factory. Retrieved July 14, 2012 .
  6. ^ Charles G. Dobson: History of the concrete roof stone . 1959, pp. 21, 24.
  7. ^ A b Charles G. Dobson: History of the concrete roof stone . 1959, pp. 21-23.
  8. ↑ Eugen Kroher 1919 in the German Tonindustrie-Zeitung, quoted from Charles G. Dobson: Geschichte des Beton-Dachsteins . 1959, p. 25.
  9. ^ Charles G. Dobson: History of the concrete roof stone . 1959, pp. 27, 29.
  10. ^ Charles G. Dobson: History of the concrete roof stone . 1959, p. 30.
  11. ^ Charles G. Dobson: History of the concrete roof stone . 1959, p. 40.
  12. ^ Charles G. Dobson: History of the concrete roof stone . 1959, p. 29.
  13. ^ Charles G. Dobson: History of the concrete roof stone . 1959, p. 36.
  14. ^ Charles G. Dobson: History of the concrete roof stone . 1959, pp. 36-37.
  15. ^ Charles G. Dobson: History of the concrete roof stone . 1959, pp. 35-36.
  16. ^ Charles G. Dobson: History of the concrete roof stone . 1959, p. 74.
  17. ↑ a b Paragraph 1 of the committee of the German Society of Manufacturers of Concrete Products in Guben in 1907, quoted from Geschichte des Beton-Dachsteins, CG Dobson, 1959, 25.
  18. ^ Joachim Hoffmann: The success story of Rudolf H. Braas . In: Friedrichsdorfer Schriften 8, 116.
  19. ^ Charles G. Dobson: History of the concrete roof stone . 1959, p. 28.
  20. ^ Charles G. Dobson: History of the concrete roof stone . 1959, pp. 26-28.
  21. ^ Joachim Hoffmann: The success story of Rudolf H. Braas . In: Friedrichsdorfer Schriften 8, 116/117.
  22. ↑ a b c d e f Joachim Hoffmann: The success story of Rudolf H. Braas . In: Friedrichsdorfer Schriften 8, 117.
  23. ^ Charles G. Dobson: History of the concrete roof stone . 1959, p. 33.
  24. ^ A b Charles G. Dobson: History of the concrete roof stone . 1959, p. 25.
  25. ^ Charles G. Dobson: History of the concrete roof stone . 1959, pp. 46-52.
  26. ^ A b Charles G. Dobson: History of the concrete roof stone . 1959, pp. 51-52.
  27. ^ Charles G. Dobson: History of the concrete roof stone . 1959, pp. 57-59.
  28. ^ Charles G. Dobson: History of the concrete roof stone . 1959, p. 24.
  29. ^ Charles G. Dobson: History of the concrete roof stone . 1959, pp. 55, 61.
  30. ^ Charles G. Dobson: History of the concrete roof stone . 1959, p. 61.
  31. ^ Charles G. Dobson: History of the concrete roof stone . 1959, pp. 61, 64.
  32. ↑ Patent DE000001631179U: Concrete roof tiles and device for their production of November 22, 1951, p. 2. German Patent and Trademark Office, accessed on July 14, 2012 .
  33. ^ Charles G. Dobson: History of the concrete roof stone . 1959, p. 64.
  34. ^ Joachim Hoffmann: The success story of Rudolf H. Braas . In: Friedrichsdorfer Schriften 8, 118/119.
  35. ↑ a b Armin Gebhardt: The brick industry from the perspective of the seventies . 1975, p. 38.
  36. ^ Joachim Hoffmann: The success story of Rudolf H. Braas . In: Friedrichsdorfer Schriften 8, 119–122.
  37. ^ A b c Joachim Hoffmann: The success story of Rudolf H. Braas . In: Friedrichsdorfer Schriften 8, 2008, p. 121.
  38. ↑ a b Patent DE000000803468B: Machine for the production of concrete roof tiles from October 2, 1948, p. 1. German Patent and Trademark Office, accessed on July 15, 2012 .
  39. ↑ Patent DE000000803468B: Machine for the production of concrete roof tiles from October 2, 1948, pp. 1-2. German Patent and Trademark Office, accessed on July 15, 2012 .
  40. ↑ Patent DE000000803468B: Machine for the production of concrete roof tiles from October 2, 1948, p. 3. German Patent and Trademark Office, accessed on July 15, 2012 .
  41. ↑ a b Joachim Hoffmann: The success story of Rudolf H. Braas . In: Friedrichsdorfer Schriften 8, 124.
  42. ↑ a b c pioneer Braas. DDH Deutsches Dachdeckerhandwerk Online, accessed on October 14, 2012 .
  43. ↑ Decision B 1 - 26401 - U - 280/99 of June 13, 2000, p. 10. (PDF; 31 kB) (No longer available online.) Bundeskartellamt, formerly the original ; Retrieved July 14, 2012 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.bundeskartellamt.de  
  44. ↑ Decision B 1 - 26401 - U - 280/99 of June 13, 2000, pp. 6–7. (PDF; 31 kB) (No longer available online.) Bundeskartellamt, formerly the original ; Retrieved July 14, 2012 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.bundeskartellamt.de  
  45. ↑ umbrella organization: Braas roof systems of 23 September 1999. (Not available online.) Db German bauzeitung, formerly in the original ; Retrieved October 14, 2012 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.wissenschaft.de  
  46. ↑ Decision B 1 - 26401 - U - 280/99 of June 13, 2000, p. 7. (PDF; 31 kB) (No longer available online.) Bundeskartellamt, formerly the original ; Retrieved July 14, 2012 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.bundeskartellamt.de  
  47. ^ Joachim Hoffmann: The success story of Rudolf H. Braas . In: Friedrichsdorfer Schriften 8, 123.
  48. ↑ Discussion of new standards and draft standards of the NABau, January 2012 edition. (PDF; 3.3 MB) DIN German Institute for Standardization e. V. - Construction Standards Committee (NABau), accessed on July 14, 2012 .
  49. ↑ DIN EN 490: 2012-01 (D). (No longer available online.) Beuth Verlag GmbH, formerly in the original ; Retrieved July 14, 2012 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.beuth.de  
  50. ↑ NORM DIN EN 491: 2011-11. Beuth Verlag GmbH, accessed on July 14, 2012 .
  51. ↑ DIN EN 491: 2011-11 (D). (No longer available online.) Beuth Verlag GmbH, formerly in the original ; Retrieved July 14, 2012 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.beuth.de  
  52. ^ Concrete roof tiles. DIN CERTCO Society for Conformity Assessment mbH, accessed on July 14, 2012 .
  53. ↑ Michael Stahr, Dietrich Hinz: Renovation and expansion of roofs: Basics - Materials - Execution . 2011, pp. 306-307.
  54. ^ A b c Michael Stahr, Dietrich Hinz: Renovation and expansion of roofs: Fundamentals - materials - execution . 2011, p. 307.
  55. ↑ Patent DE000001807203U: Concrete roof tile with auxiliary rib of November 24, 1959, p. 1. German Patent and Trademark Office, accessed on July 14, 2012 .
  56. ↑ Patent DE000001125629A: Concrete roof tiles for a roof covering without transverse folds from December 7, 1959, p. 1. German Patent and Trademark Office, accessed on July 14, 2012 .
  57. ↑ Patent DE000001806721U: Concrete roof tiles with auxiliary rib from December 21, 1959, pp. 3-6. German Patent and Trademark Office, accessed on July 15, 2012 .
  58. ↑ Patent DE000001924341U: Process for the production of a storm-proof concrete roof tile from March 19, 1962, pp. 3-6. German Patent and Trademark Office, accessed on July 15, 2012 .
  59. ↑ Patent DE000001884754U: Concrete roof tiles with storm protection from June 27, 1963, pp. 3-6. German Patent and Trademark Office, accessed on July 15, 2012 .
  60. ↑ Patent DE000001609924B: Betondachstein from February 8, 1966, p. 2. German Patent and Trademark Office, accessed on July 14, 2012 .
  61. ↑ Patent DE000001977166U: Concrete roof tile with side interlocking from July 28, 1967, pp. 3-6. German Patent and Trademark Office, accessed on July 15, 2012 .
  62. ↑ Patent: Process for the production of concrete roof tiles with a naturally rough surface from June 4, 1987. PatentDE / Braas & Co GmbH, accessed on July 14, 2012 .
  63. ↑ Patent DE000008903375U1: Dachstein, in particular concrete roof tiles produced using the strand process, dated June 15, 1989, p. 2. German Patent and Trademark Office, accessed on July 14, 2012 .
  64. ↑ Record pan: The world's largest Dachstein is now in Heusenstamm, dated February 10, 2012. Peter Petrat, Offenbach-Post, accessed on March 26, 2013 .
  65. ^ LCA comparison of roof tiles and Dachstein, pp. 1–2 and p. 26, dated February 7, 2008. (PDF; 504 kB) Öko-Institut eV, accessed on March 26, 2013 .