Plaster base

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The use of plaster bases is a well-tried method for cleaning surfaces that are actually not or inadequately suitable as a plaster base. Reed mats ( reed fabric ) and diagonally nailed (semicircular or trapezoidal ) wooden rods are examples of the variety of plaster bases used in the past, which are increasingly being replaced by modern fabrics today.

Plaster base with wooden sticks

Architecture and building design, building physics requirements (e.g. thermal insulation ), climatic influences ( temperature and humidity ) and structural necessities make the use of different building materials within an area to be cleaned necessary in today's building methods. The resulting increased demands on the plaster can only be met with additional measures (plaster base, plaster reinforcement ) which contribute to a significant reduction in the risk of cracks and simplified and permanent assembly.

An extensive range of plaster bases and reinforcements was developed to meet the structural requirements.

term

Plaster supports are constructive aids that are used to create a plaster shell that is largely independent of the substructure (e.g. masonry, wooden posts). A plaster base is an independent plaster base that is able to permanently support a plaster / mortar layer. Plaster bases cannot replace plaster reinforcements. According to ÖNORM B 2210, 1.3.3 (12) and ÖNORM B 3346 5.5.2, the plaster base is a separate plaster base. Plaster bases have the task of bridging unsuitable or missing plaster substrates (e.g. cracks, material changes in the substrate, slots and / or openings). The plaster base creates a plaster base suitable for plastering and has to carry the own weight of the plaster mortar, on facades also wind pressure and wind suction, via the fastenings and / or anchors in the solid, solid subsurface or in the substructure. Plaster bases can consist of reeds, wire brick mesh , expanded metal ( Rabitz ) and bonded wood wool panels.

history

From ancient times to the industrial age

Because plaster does not adhere well to smooth stone or wooden surfaces, appropriate links were used between such surfaces and the plaster from the earliest times.

Markus Vitruvius Pollio , or Vitruvus for short, hasalready dealt with comparable structural problemsin his work “Ten Books on Architecture” (De Architektura Libri Decem).

While Antonio Averlino Filarete , or Filarete for short, deals very little with plaster base, Leon Battista Alberti (1404–1472) deals with this topic in more detail.

The use of plant fibers , cane stalks and wooden sticks for the production of plaster bases has been perfected in the craftsmanship over time so that many plastering work has been preserved to our days without significant damage. The plastering industry flourished particularly in the Rococo (1720–1775). Important artists created brilliant works of art. In the series of publications “Die Künstler Wien”, which is based on the rich source material of the Vienna City Archives , L. Sailer worked on the sub-area on “Die Stukkateure” . In Sailer's writing the development of the plastering trade, an alphabetical list of the well-known plasterers (with dates of their lives) is given, and in a supplement also the privilege of 23 May 1709 for plasterers. Already from Leon Battista Alberti (1404–1472) remarks on wickerwork in walls, which he calls “mere crusts” instead of “shells” (in the translation by M. Theuer ), it can be seen that wickerwork as a plaster base also has a static and constructive significance comes to. There was still a long way to go from the use of the clay with the wattle to the connection of concrete with iron . In 1860, the Parisian gardener Joseph Monier embedded iron wires to reinforce the concrete from which he made his flower pots . In 1867 he took out a patent for the production of portable containers made of cement mortar with iron inlays, which was followed in 1878 by an additional patent as the actual Monier patent.

The development up to the 19th century

From a historical point of view, one essentially differentiates

  • Plaster mortar carrier made of individual small elements,
  • Plaster mortar carrier made of panel elements with a rough surface,
  • Plaster mortar carrier made from connected braids or nets

The plaster mortar carriers made of individual small elements, for example from wooden strips, pipe stems, plasterboard and so on are only used in Austria in individual special cases in construction, for example to secure the plaster over wooden frameworks, to secure the plaster in individual stone wall designs and the like more. The use of this type of plaster mortar carrier is limited to individual cases, as it takes a lot of time and is expensive. Nevertheless, the plaster mortar base consisting of individual elements is to be cited as the origin of the plaster base in the overall representation.

The plaster mortar carriers made of plate elements with a rough surface primarily comprise the groups of wood wool or wood wool fiber board elements. These panel elements fulfilled a valuable function in the building industry in their natural area of ​​activity. The majority of these products do not have the necessary durability and fire safety for the requirements placed on plastering mortar substrates. Technically, these panels have completely different functions in heat and sound insulation , as a base for floor coverings , lining interiors and so on.

Plaster mortar carrier made from connected braids or nets. The cane farmers on the Berlin Lake District , who supplied the city with loose reeds , were the first to begin - at the suggestion of a weaver - at the beginning of the 18th century to interweave the reed stalks with bast, then with hemp splint , and later still with binding wire they used primitive looms , which are still in use in some places to this day. Around the middle of the 19th century, the builder Carl Stauss from Finsterwalde invented the first mechanical tube loom to improve these previously primitive weaving methods. He supplemented the primitive product of the Brandenburg house industry by inserting a 1 mm thick warp wire, which, woven in at a distance of 15 to 20 cm, made the subsequent attachment of support wires unnecessary for tubular fabric designs. These types of tubular fabric have survived to this day. The reed fabric completely displaced the individual fastening of pipe stalks to wooden formwork or battens and enabled much faster construction progress through the mechanical weaving of the reeds into fabric fabric mats.

The mechanical interweaving of the reed stalks was forced into four specific processing methods by the shape and size of the natural product:

  • The simple tubular fabric: Here the stems are arranged at intervals of approx. 5 to 10 mm from one another and either tied with a strong wire or held with warp and warp wires of equal strength. The simple tubular fabric is used in construction for the production of ceiling soffits, but also for cladding wooden walls, etc. In a simple position it is processed on more or less non-arranged formwork, under reinforced concrete ceilings without any formwork, in such cases laid crosswise and with stronger reinforcing wires supported.
  • The double pipe fabric , which is mainly used in the countries belonging to the Swabian cultural area, is a fabric in which pipe stalks come to lie above and below the strong warp wire. The purpose of this arrangement is to achieve a stiffer fabric in which it is possible to save on wooden formwork when processing ceiling soffits.
  • The dense tubular fabric is characterized in that stem to stem are interwoven in such a way that penetration of the mortar is prevented. This third form of reed fabric, however, already represents a transition to the formwork itself and is also used exclusively as such, for example primarily in reinforced concrete ceilings to form the tubular cell hollow bodies.

The tubular fabric mats, in which only the thinnest stalks and stalk tips are pressed together to form a dense 1 to 1.5 cm rollable layer and at the same time woven, represent a transition from woven plaster mortar carriers to those of the panel systems. The tubular fabric mats are probably also used for construction projects, but are primarily intended and used as a thermal protection element. Weaving the reed stalks had to trigger the thought, even the strips of wood used as plaster carrier in wood richer areas with wire to a tissue processing. This is how the wooden rod mesh was created. There are also several types of single and double fabric and, moreover, all possible triangular, square and trapezoidal cross-sections with different wire connections, depending on the possibilities of designing the wooden rods differently. It was also an obvious step to interlock the wooden sticks with notches and thus make them more suitable for clasping the mortar. Completely different from this in Central Europe, which was still used quite frequently around 1933, is the wood-chip weave used in southern France until the middle of the 19th century. In this plaster mortar carrier, about three centimeters wide wood chips are intertwined like a mesh. These were used in not too large, bendable, but not rollable elements by nailing them to the correspondingly spaced trams (supporting beams) as plaster mortar supports for ceiling soffits. All these plaster mortar carriers made of reed or wood have more or less common features that cellulose-containing bodies have in general, and especially in construction. We find these disadvantages to the slightest extent in the case of reeds, which, due to the soil silicates absorbed during growth, participate in a kind of petrification process after cutting and drying. Of course you have to be careful not to weave undried, still green reeds or to use such woven rolls in construction. In cases of fire Reed has proven itself as a plaster base generally good, only when the heat generation lasts longer passes through the expansion of the included in the individual Rohstängelzellen, more heated and therefore expanding air with bright-like explosions bursting around the plaster surface one. In the case of wooden rod meshes, there is a risk of shrinkage during drying and swelling in high humidity, especially if these plaster mortar carriers are not completely embedded in the mortar. The often heard claim that the moisture in the mortar that has been thrown on already causes the wood to float and that the plaster must consequently develop shrinkage cracks when it dries out is unsound. The fact is, however, that only relatively thin wooden strips can be processed into wooden rod meshes, since with a thicker cross-section the drying out after plastering would be irregular and the parts not covered by the plastering would dry out sooner than those embedded. All reed and wooden stick fabrics are peculiar to the fact that, depending on the structure of the stems or sticks, they can be rolled, but not bendable in every direction. The briefly indicated disadvantages of the cellulose-containing plaster mortar carriers have resulted in the increasing use of iron wire mesh in construction. There are also various types of plastering mortar carriers made of wire mesh, which differ partly in the geometric arrangement of the wires and partly in the pressing out of mesh grooves for the purpose of a closer bond with the plaster mortar. These iron wire cloth, commonly known as Rabitz become known, for deposits in cement - or lime mortar delivered bare, however, ver zinc plated when using plaster - you want to work or gypsum lime to a United rust by the sulfur compounds to prevent the gypsum. All designs on Rabitz fabric are characterized by their absence of cracks and great fire safety when properly executed. But the work is by no means easy, and only the addition of hair to the plaster mortar enables the plastering mortar to be properly applied.

The invention of the stauss brick fabric

Around 1880 the Prussian Ministry of Agriculture appointed the most important plasterer pipe fabric factories in Germany at the time , the brothers Paul, Max and Otto Stauss from Cottbus , to inform them that plasterer pipe fabric could no longer be used for the stables of the state domain, namely for the breeding studs , since in repeated cases damage to the eyesight of the animals has occurred due to the falling off of mortar particles . This crumbling is due to the fact that the cellulose-containing plastering mortar carriers - due to their hygroscopic properties - develop fine hairline cracks, which expand relatively quickly due to the ammonia vapors rising in the stables and then cause the aforementioned problems. The use of the usual Rabitz nets seemed cumbersome, the pure lime mortar prescribed for stables would not hold up without the quickly setting gypsum additive . The task to be solved now was to find a new plaster mortar base that would meet all requirements. The result of the several years of tests that were started was a plaster base consisting of a steel wire mesh, at the intersection of which diamond-shaped buttons are pressed and fired as hard as a brick. The invention of the wire brick fabric, which was named after the inventors "Staussziegelnetz" and which at the same time meets all the requirements that modern technology places on a modern and high-quality plaster mortar carrier, proves how far ahead European ingenuity was of its time. In 1889 Paul Stauss in Cottbus received the first patent (DRP. 51.158) for his invention of the wire brick fabric. This Paul Stauss is none other than the grandson of the master builder from Finsterwalde who set up the first mechanical tube loom. This family has made two decisive contributions to the development of the plaster base. The invention of the gauze brick fabric was far ahead of its time and, with an almost strange clairvoyance, already anticipated developments that were only widely used much later with the advances in steel and reinforced concrete construction . We have to go back in time to fully grasp the purely technical achievement. At that time, the pipe mesh was still the glossy product among plaster mortar carriers, and Rabitz had only just begun to use iron wire mesh for plastering purposes in the Berlin building industry. Reinforced concrete technology was still in its infancy, the static calculation of such structures was an area that was only just beginning to be explored.

The millennia-old brick tone, reduced to a minimal cross-section and reinforced with steel inserts, these are terms for every economically thinking, modern technician that go far beyond the meaning of a plaster mortar carrier. And so we move from the form-giving characteristic to constructive problems, which to determine and evaluate is another task worthy of thanks. The investigations and calculations that have been carried out up to now with structural brick fabric alone and with components that were made with the use of wire brick fabric, and the great application possibilities that result from this, are reported separately. They provide evidence that the use of the structural brick fabric in the building industry has made fundamental progress possible and that significant further improvements of a constructive and economical nature can be achieved if the structural brick fabric is properly brought to its full effect in terms of statics, construction and craftsmanship.

Rudolf Sailinger generally assessed this design in the following wording: “The retaining brick fabric is a further development and perfection of the Rabitz network through fired clay elements. This creates a number of noteworthy new properties that improve and expand the intended use. This includes increased security against cracks and advantages of the execution. The technological properties, the static function of the dunnage fabric and its tensile and bending resistance have been researched through rigorous research in scientific material testing institutes. The resistance to dynamic effects, frost and fire as well as the thermal insulation were determined perfectly. In summary, it can be stated: The gauze brick mesh has permanent and directional importance both as a plaster base and as a reinforcement network in the static sense of reinforced concrete construction, in particular for force distribution and absorption of vibrations in slabs, for shear reinforcement in beams and constriction in columns. "

Today, Stauss is not a brand name, but rather describes a type of product that is also called (wire) brick mesh. Stauss brick fabric is produced by many companies around the world and is one of the most important representatives of the plaster base.

Adhesion of the plaster to the plaster base

The adhesion of a plaster has three main causes:

  • Adhesion of the wet fresh mortar
  • capillary absorbency of the plaster base
  • mechanical adhesion by "clawing" on the plaster base surface

Adhesion: wet adhesion

Throwing or spraying the wet fresh mortar onto the plaster base creates a temporary negative pressure at the contact surface between the mortar and plaster base . This is necessary for the fresh mortar to adhere to the plaster base at the time the plaster is applied. If a layer of plaster that is too thick and / or too heavy is applied to a very smooth, non-absorbent plaster base, it slips off; it falls off because it has no or too little adhesion.

Capillary absorbency

The binding agents ( lime , cement , plaster, etc.) contained in the fresh plaster mortar are sucked into the plaster base ( capillary suction capacity ). In the capillaries , the binders react with the water ( hydraulically ) or with the air ( CO 2 ) and begin to crystallize there . The resulting crystals are pressed into the capillaries or pores of the plaster base and “matted” the plaster layer with the base. If a plaster base is too absorbent, it removes the water from the fresh mortar too quickly. The plaster is "dying of thirst". The binders have no way of reacting sufficiently. A weak “matting” due to reduced crystallization therefore leads to less adhesion of the mortar layer to the plaster base.

Mechanical adhesion - claws

The stiffening or hardening plaster mortar is given an additional connection to the sub-floor by laying down in all depressions or elevations of the plaster base while it is still plastic and can therefore “claw” there when it has set. Therefore, a rough plaster base is more suitable than a smooth one.

Working together

As a rule, all three parameters act one after the other (e.g. adhesion → absorbency, adhesion → clawing) and also side by side (e.g. adhesion + absorbency, absorbency + clawing).

The difference between plaster base and plaster reinforcement

Only through the type of location (or due to any attachment in the subsurface) of the grids and fabrics used is their function as a plaster base or as reinforcement determined. A plaster base can take on the function of a plaster reinforcement under certain conditions. A plaster reinforcement (wire mesh, textile glass mesh, etc.) cannot, however, take on the function of a plaster base (stauss brick mesh, etc.).

A reinforced pre-splitter takes on the function of a plaster base ( when connected).

A plaster reinforcement is an insert in the plaster or in a filler layer. It improves the tensile strength of the plaster or the filler.

A plaster base is also embedded in the plaster, but is self-supporting.

In special applications, the use of a plaster base and the additional attachment of plaster reinforcement can be advantageous.

Examples:

Types of plaster bases

Expanded metal and wire mesh

Rabitz grids are often made of expanded metal or galvanized wire mesh and are used to manufacture Rabitz .

Reed mats

Reed mats consist of reed that is tied with galvanized wire in a simple, semi-tight or tight manner . Tube mats are produced in mat form but also in rolls. Reed mats are usually no longer used as a plaster base in new buildings, but they are used in ecological or biological construction and in the area of renovation and / or restoration of old or historic plastered surfaces. Compared to more modern plaster bases , reeds are organic , so they can react to moisture and also require a flat surface. In the case of plaster damage, especially outdoors or other moisture problems, reed mats can rot over time.

Fibreboard

Wood wool with mineral binders, especially cement or magnesite.

Wire brick mesh

Wire brick mesh is a plaster base with a brick surface. The standard wire mesh is a square wire mesh with a mesh size of about 2 cm with clay lozenges / clay crosses pressed and fired at the intersections. The openings in between make up about 25% of the total area. It is manufactured in rolls and mats in accordance with ÖNORM B 3645. The fresh mortar penetrates through the openings and spreads out to form mushroom-shaped plugs on the rear side, thus creating a non-positive bond with the plaster base. The mortar also adheres to the clay lozenges of the wire brick mesh due to its capillary absorbency.

Possible applications

Interior plaster:

Fire protection

Non-combustible plaster bases are suitable for the fire-safe cladding of components and pipes.

With regard to the type of plaster, plaster thickness and plaster reinforcement, the manufacturer's regulations and in particular ÖNORM B 3800, parts 1 to 4 must be observed. In Germany you can find information on this in DIN 4102 Part 4.

Chimneys in a brick wall

The chimney ( chimney ) can be seen as a statically independent structure. Technically easy to manage is a construction in which the chimney is on or next to the wall and guides it past him without interruption. For optical reasons, however, the chimney is usually flush with the wall on one side, so that the wall is on both sides of the chimney; on the other side, the flue protrudes from the wall.

If a plaster base is only attached to the left and right of the masonry on the flush side, the plaster base carries the plaster shell in the area of ​​the chimney. If there is a separating layer (e.g. bitumen paper) between the plaster base and the chimney, the chimney can move slightly behind it.

On the protruding side, the chimney should be covered with a plaster base. The resulting “sleeve” around the chimney creates a crack-free plaster bowl that is largely independent of its movements.

Plaster over a moving surface (e.g. wood)

If the uninterrupted cleaning of wooden components is required, a separating layer (e.g. pore-open bitumen paper) must be placed between the plaster base and the wooden surface.

However, wood does not only change when exposed to moisture through the plaster mixing water, which is reduced by the bitumen paper, but also reacts differently depending on the season and climatic conditions.

Foils are not suitable as a separating layer because there is a risk of mold .

The plaster base must never be attached to the wood itself, otherwise the movements of the wood will be transferred to the plaster shell.

Exterior plaster:

Plaster over insulated components

Venetian blind boxes, building base insulation, ceiling edge insulation, etc. are always the cause of cracks in the facade plaster . In most cases, inadequate plaster reinforcement, combined with the plastering work being carried out too quickly (insufficient drying of the individual plaster layers), is responsible for this.

The use of plaster bases and the professional attachment to stable masonry are more expensive, but reduce the risk of cracking significantly.

literature

  • F. Baravalle-Brackenburg: Stauss brick fabric. Shaping and constructive element in construction. Bohmann, Vienna a. a. 1953.
  • ÖAP: Processing guidelines for plaster bases . Innsbruck 1996.

Individual evidence

  1. ↑ ÖNORM extract DIN 3645 (PDF; 2.9 MB)