Plaster (component)

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Plastered wall in Pompeii (79 AD)
Damaged plaster on a residential building

As a plaster or plaster refers to a coating on the outer and inner walls and on ceilings in construction. A structure with external plaster is also known as a plastered structure.

Depending on the type of application, the plaster fulfills various purposes as a component, from the production of a smooth substrate for coating, tiling, painting or wallpapering to large-area structural design. Tasks that go beyond the appearance are the regulation of room humidity for interior plastering, thermal insulation and water repellency for exterior plastering, fire protection and soundproofing. Plasters consist of several coordinated layers that together form a plaster system.

Plaster mortar and other coating materials are used as building materials , often supplemented by reinforcements, building boards and prefabricated elements. One speaks of "dry plaster" when the cladding is made using drywall .

Word origin

Putz was in the 17th and 18th centuries from the word brush formed. The verb used since the 15th century originally meant "remove the slug (impurity, lumps of dirt, lumps)" (the word is preserved in the slug disk ). From this the two meanings "clean, clean" and "beautify, decorate" developed. Today's compound words such as house cleaning and spring cleaning are linked to the importance of cleaning . The meaning of decorating can be found in old terms such as headdress or plasterer , both terms are in plastering "throwing mortar on walls".

Plaster in the actual sense only means the aspect of the clean and decorative final coating (to which a coloring may be applied), the aspect of the leveling layer when tiling and wallpapering falls under the term mortar (Latin mortarius "that finely ground in a mortar"). Therefore, one speaks in general expressly of plaster mortar when one means the material, and of plaster / plaster when one means the final plaster.

Types of plaster

Plaster can according to the materials used, i. d. According to the binding agent (lime plaster, lime cement plaster, cement plaster, gypsum plaster, clay plaster, silicate plaster and organic synthetic resin plaster), according to the location of the mortar production (factory dry mortar, construction site mortar), according to the type of mixing (hand plaster, machine plaster), after the surface treatment ( Scratch plaster, rubbing plaster, trowel throw plaster, trowel scratch plaster), differentiated according to function ( thermal insulation plaster, acoustic plaster, renovation plaster, magnetic plaster) or according to the thickness of the application.

The term “ organic ” in this context means that the properties of the material in question are mainly determined by the synthetic resins it contains. In contrast, a " mineral plaster" contains only a few and a "purely mineral" plaster no synthetic resin at all.

Plaster construction

Spray grout or pre- spray (adhesion promoter): Thinly mixed spray grout is thrown with a trowel or a brush onto less absorbent or smooth surfaces (e.g. concrete) like a net, i.e. not covering it. The spray grout is thrown onto the entire surface of highly absorbent (e.g. low-fired bricks, plaster of paris or clay) or uneven surfaces (different materials).

Bonding bridge : Instead of spray grouting, organic bonding bridges are often used on concrete surfaces, e.g. B. used for the subsequent application of gypsum plaster, or mineral adhesive bridges to pretreat the substrate for lime-cement plasters.

Concealed plaster (base plaster): On normally absorbent substrates, the concealed plaster can be applied directly to the substrate in thicknesses of 1 to 3 cm (in special cases up to 10 cm). The plaster is intended to level out any unevenness. If the layer thickness required for equalization varies by more than 5–10 mm, however, the deeper areas have to be filled beforehand, as otherwise the plastered surface cannot be peeled off evenly. If they are not bundled, however, individual pipes and cables can usually be embedded in the concealed installation. The sub-plaster serves as a carrier for finishing plasters (finishing plasters). Traditional base coats usually contain various types of lime (often with cement) or plaster as binding agents. They are sometimes used indoors as a substrate for wallpaper or paint. Plasters with a higher proportion of cement are used as base plasters or in damp rooms (e.g. basements and bathrooms) and as a base layer for hard wall coverings (natural stone, tiles).

Finishing plaster : The finishing plaster is the last layer of plaster of a plaster system in the exterior and interior. It can be implemented as a thin layer plaster (organically bound plaster, layer thickness = maximum grain thickness) or thick layer plaster (predominantly minerally bound plaster, layer thickness> largest grain). Mineral-bound finishing renders are more favorable in terms of building physics, but usually require a leveling coat for a uniform appearance and for weather protection.

Further classifications:

According to order size

Traditionally, thick- layer plasters are used, which are applied in an application thickness of at least twice the diameter of the largest grain of the aggregate . Mostly a maximum grain of 2 to 8 mm was used. The typical application thickness is 10–15 mm for interior plaster and 15–20 mm for exterior plaster.

Some coarse finishing plasters are processed in a smaller thickness in order to produce a special surface structure:

  • Spray plaster is mixed relatively liquid with a maximum grain size of up to 8 mm (rarely up to 16 mm) and thrown over the base plaster like a full-surface spray coat.
  • In the case of scratching, rappelling and rubbing plasters, it is sometimes desirable that the largest grain is dragged along when removing or rubbing off the stiffened plaster, leaving indentations on the surface. For example, when towing plaster or Munich rough plaster , also called slider and because of the furrows as Made plaster or worm plaster are called.
  • By washing out the binding agent and fine grain, the coarse grain (as with exposed aggregate concrete ) appears decoratively from the surface.

Modern thin-layer plasters usually contain synthetic resins and other additives which, by delaying drying out, increasing the binding force and improving the processing properties, enable application thicknesses from around 3 mm. Filler compounds can sometimes even be drawn out “to zero”. The trade also calls thin-layer plasters to express the fact that specially selected aggregates are used and the properties of the plaster are modified by additives. Thin-layer plasters are often used to rework existing plastered surfaces and as a decorative top coat for thermal insulation composite systems. In order to avoid cracks, reinforcement in the form of a fiberglass fabric is often incorporated.

Smoothing, welding and slurry plastersare applied in a thickness of a few millimeters to unify the surface of the base plaster, to smooth it or to close pores. If the plaster surface underneath has not yet fully set or is very thoroughly pre-wetted, such thin plaster layers can also be used as pure lime plasters without the addition of organic binders. While smooth plaster in the form of a filler compound is often used to produce a wall surface that is as flat as possible, welding plasters and especially paste-like to liquid slurry plasters are used to smooth uneven surfaces without completely leveling the existing unevenness.

According to material

  • Clay plaster : Clay is the first plaster material used by mankind. Clay plaster is easy to process, versatile, very open to diffusion and createsa healthy indoor climatethanks to its extreme sorption capacity. Since clay plaster is sensitive to moisture, it should not be used on the weather side of buildings or in damp basements.
  • Lime plaster and lime sludge : Mostly used as plaster for historical buildings due to its low strength and better stress absorption. Requires skilled craftsmen and longer drying times for processing. Lime plaster is ecological and has a fungicidal effect. It is open to diffusion and ensures a very good indoor climate.
  • Lime cement plaster : Classic plaster for inside and outside. Often also used as a lightweight lime-cement plaster (contains tiny styrofoam beads or mineral aggregates, e.g. pumice or expanded glass) on facades and in damp rooms. Lime cement plaster has a higher compressive strength than pure lime plaster and is also open to diffusion and less sensitive to moisture. Due to the cement content, however, it is not very suitable for the high-quality repair of historical buildings.
  • Gypsum plaster and, depending on the ingredients Anhydritputz , Gipskalkputz , Kalkgipsputz or gypsum-cement-lime plaster : Mostly used as a smooth or verriebener plaster for indoor use. Often intended to be coated with wallpaper. It may be used in damp rooms up to exposure class W3 (i.e. domestic kitchens and bathrooms), but not in commercially used wet rooms, garages or the like (exposure class W4). In the outdoor area, plaster containing gypsum is only used in exceptional cases in the renovation of monuments to recreate historical plaster mixtures.
  • Fine lime plaster , such as smooth lime ( white lime burnt at low temperatures , also with the addition of white marble powder), stuccolustro (Italian, translated "shiny plaster"; lime plaster processed with wax ), marmorino (also called stucco veneziano ; with colored marble powder; in several layers applied and densified) or Tadelakt (made waterproof with soap).
  • Pozzolan , pure or as an additive to plasters and cocciopesto (with the addition of brick flour )
  • Trass lime and trass cement plaster
  • Cotton plaster : Wall and ceiling coating for interiors, which consists of cotton fibers and various fillers and effect materials. Cellulose acts as a binding agent. Cotton plaster and other natural fiber coatings are usually used as a top coat instead of wallpaper or a rub or scratch plaster.

According to the surface design

Rough plaster / rubbing plaster with colored stripes
Outer wall of the Ruchenberg ruin : Rasa-Pietra with grout

In the course of history, a large number of plaster structures and two-dimensional design patterns have developed, which, like other design features of a building, can be assigned to the various architectural epochs.

  • Smooth plaster or smooth plaster : With the help of a smoothing trowel , straightening iron or polished stones ( Tadelakt ), the surface of slowly setting lime or clay plasters is smoothed once or several times ( stucco lustro ). Modern synthetic resin-bound smooth plasters are also filled and sanded. Smooth plaster outdoors is susceptible to cracking, often does not compensate for moisture and often appears uneven in grazing light.
  • Reibeputz and disc plaster : a finishing coat obtained by the use of a wooden or plastic board or rubbing with steel trowel or sponge disc with a circular motion and is rubbed by the moisture of the not yet solidified plaster. Using different grain sizes (up to 5 mm grain size) of the plastering mortar and various rubbing movements, the usual structures can be achieved, which are regionally known as Munich rough plaster, grooved plaster, worm plaster, maggot plaster or bark plaster, etc. The rubbing and felting of external plaster should be avoided, as it leads to the accumulation of the binding agent on the surface and thus to its hardening and susceptibility to cracks. For the same reason, interior plaster should not be worked on for too long with a grater or felt board.
  • Rough plaster : Through traditional and often regionally differentiated treatment during or after application, different surface effects are achieved. The rough plasters include, for example, spray plaster, barley plaster, knotted plaster, as well as:
    • With scratch plaster , usually after 12 to 36 hours, before the final hardening, the top layer of plaster is scraped off, often with nail boards such as hedgehogs or steel nail scrapers. This results in a rough, but crack-free plaster, as the tension-laden sintered layer is removed, which forms when fine and medium-fine plasters are applied because the binding agent migrates to the surface. A particularly strongly structured surface is obtained by using a coarse grain size of up to 4 or 8 mm. After the first pressure-resistant setting, the plaster is then scratched with a nail board or a coarse saw blade as soon as the grain on top jumps out of the plaster and no longer sticks to the tool.
    • Rappputz is roughly peeled off ( tapped ) with the edge of the trowel after it has been started . Depending on the consistency of the plaster, the result is a more or less irregularly structured and, depending on the grain size, often very coarse surface.
  • The surface of the structure cleaning is after application by processing with a trowel, the trowel , the brush or other tools designed (z. B. Besenwurf- / Besenstrich- / Besenstipp- / Besenzugputz, Draufelstich, trowel plaster trowel bar plaster trowel casting plaster, comb plaster, Combed plaster, nail board plaster, patch plaster, brush plaster, wash plaster).
  • Stone plaster was used until the 1960s for the production of components with chafed surfaces that resembled natural stone. The hardness of the aggregate is selected to match the strength of the binding agent, so that the plaster can be worked on like a stone cutter after it has set .
  • Schlämmputze and coating plasters and welding plasters are often used to revise the coarse pored surface, cracked old plaster or as a thin (steinsichtiger) coating on natural stone or brick walls. Sludge , which has a consistency between the paint and the plastering mortar , was traditionally used to coat coarse spray and throw or porous scratch and black plaster. The result is a lively surface that is fine-pored enough to be used on weathered surfaces without any further painting.
  • In medieval buildings such as castles, the rasa pietra technique (= stone that has passed through) was often used. With this technique, the mortar is applied generously along the joints of the masonry stones and spread until the wall has formed an almost flat surface, but the stone heads remain uncovered or are exposed again by rapping . Sometimes the joints in the damp mortar are decorative drawn ("joint line"). In the case of the “bandage plaster”, on the other hand, the joints are raised as narrow bulges.

In the case of exterior plaster and especially for grout , the plaster mixture must not achieve a higher strength than the substrate, as otherwise moisture and frost-related swelling and shrinking as well as thermal stresses from solar radiation can lead to accelerated weathering of the masonry.

Other ways of applying the plaster or processing the surface are abrasion, fine draft, modeling plaster, natural plaster, roll plaster, rustic plaster, piercing plaster, stamp plaster, stick plaster, roller plaster and wash plaster.

According to function

  • Universal plaster: Nowadays, mortar manufacturers add synthetic resin components to every plaster that is not specifically intended for the preservation of historical monuments. Universal plasters contain large amounts of synthetic resin and often fibers , so that they can also be applied to uneven, uneven and differently absorbent substrates. They are therefore also offered as renovation plaster , thin-layer plaster or adhesive plaster and can often be applied in layers of 4 mm or more .
  • Thermal insulation plaster: Since light plasters with a high proportion of pores are only weatherproof to a limited extent, they are usually covered with a slurry or a thin fine plaster . They are mainly used to maintain the facade structure in the renovation of old buildings, as a thermal insulation composite system is more cost-effective and more effective in new buildings . So-called condensation plasters with large capillary volumes have been developed to eliminate mold problems and are applied to interior walls. It should be noted that with interior insulation, the dew point is shifted to the inside of the (shell) wall. Ordinary insulating plasters are not suitable for permanently damp masonry or for the plinth area.
  • The common base plasters are mostly cement-containing barrier plasters which allow water vapor to pass through, but are slightly hydrophobic . In the case of permanently damp masonry, the salts transported by rising damp can crystallize between the masonry and the plaster and remove the plinth plaster over a large area. Soft sacrificial plasters or special renovation plasters can help .
  • Pure air-lime plasters are used as sacrificial plasters , which are used, especially in monument protection, to absorb building-damaging salts over a certain period of time. If the surface shows excessive efflorescence, it will be chipped off and replaced. This is particularly useful for renovation measures after floods or generally after a building has been drained.
  • Renovation plasters are highly hydrophobic , lime-cement plasters with special air-entraining agents, the structure of which promotes the evaporation of rising moisture within the plaster layer, whereby the remaining building-damaging salts are stored in the plaster structure. This minimizes visible damage caused by crystallizing salts until the pores are filled with salt. It is criticized that the cement contained can in unfavorable cases contribute to the salt load of the masonry. WTA renovation plasters are certified by the Scientific and Technical Working Group for Building Preservation and Monument Preservation . Certification and application are regulated by WTA information sheets.
  • Acoustic plasters are light plasters with a large pore volume that should not be painted over so that the sound can be absorbed by the open-pored plaster.
  • See also: hydroment .

processing

Plaster can be applied by machine or by hand. Depending on the nature of the surface of the finished plaster, one speaks of grated, textured or brushed plaster. The different grain sizes of the aggregates and different treatments of the fresh plaster (smoothing, trowelling, scratching, sweeping, ...) create different effects.

If the plaster has no further surface design after application , the type of application also determines the appearance of the finished plaster surface:

  • Trowel plaster is created by applying and spreading the plaster mortar in a fan or flake shape. Often used in subordinate rooms (such as basements) and usually only in one layer.
  • Trowel plaster gets its typical and eponymous structure by throwing lumps of mortar onto the masonry. As a rule, a plaster mortar with a grain size of up to 10 mm is used and a single layer is used.
  • Spray plaster is traditionally sprayed onto the masonry by hand or with a spray plastering device in one or more layers with a fine-grained (up to about 3 mm grain size) and thin-bodied plastering mortar.
  • With the Shine bead form applied plasters and gypsum plasters are usually beginning after application (using the plasterer's float subtracted) and then with a trowel ( trowel smoothed).

A plaster system usually consists of several layers. Mineral plasters are traditionally in an approximately 1.5 cm thick layer cranked and thus can be used as an alignment layer for irregularities in the surface. Many synthetic plasters that the outer conclusion of a thermal insulation system formed are, however, very thin mounted (z. B. "in grain strength," d. E. About 3 to 5 mm thick).

To prevent the formation of cracks in the plaster and to increase its resistance, reinforcement (reinforcement) can be helpful. For this purpose z. B. Glass fiber fabric inserted into the base plaster and incorporated with a trowel.

Cleaning rules for external plaster

The traditional plaster rule is that successive layers of the substrate, pre-molded , upper and lower plaster should always be softer. In this way, the formation of cracks and the shell-shaped detachment of plaster layers with too great a strength is avoided. Classic soft lime plaster is relatively elastic and can easily absorb tensions caused by solar radiation, moisture and frost. Since air-lime plaster absorbs a lot of moisture, the weather sides were protected from driving rain with lime sludge, lime paint , boarding, shingles or large roof overhangs.

With modern thermal insulation plaster and thermal insulation composite systems , this rule is reversed. The formation of cracks is avoided by inserting reinforcement fabric and adding synthetic resins , which make the plaster more elastic. The plaster layer can be seen as a separate shell. There is no detachment from the substrate, as the underlying insulation layer elastically decouples the plaster and allows thermal expansion . Finishing plasters with a high synthetic resin content hinder the moisture exchange. This can lead to algae growth on the surface and, in the case of water damage, to moisture accumulation in the wall and insulation layer.

function

Location Thermengasse in the Roman vicus Turicum ( Zurich ): Remnants of plastering from painted walls from the thermal baths, according to the style from the 1st century AD, with strong colors: yellow, red and black
Location Thermengasse : Remnants of plaster from painted walls from the 2nd / 3rd centuries. Century AD with fine colored lines on large white walls

Wall plaster is used for the visual design of visible surfaces and for protection against harmful effects or as a basis for further coatings such as paint, tiles or wallpaper.

Protective functions:

Special design functions:

  • In a fresco , the fresh plaster is painted with lime paint , which causes the paint and plaster to harden together to form artificial limestone
  • With stucco marble and stuccolustro , special additives and pigments are transformed into a marble-like surface by polishing and waxing.

Modern lightweight plasters or ultra-lightweight plasters were developed in order to plaster the increasingly lighter and highly insulating wall formers.

materials

Plasters can consist of many different materials. Traditionally they consist of binding agents , aggregates and water. Quartz sand, gravel, rock powder and brick chippings are mineral aggregates. Supplements such as straw, animal hair, fiberglass and flour, etc. a. are often added for reinforcement, structure formation or coloring and lightweight aggregates such as vermiculite, foam glass granulate, cork, expanded clay, EPS and the like. a. to reduce the thermal conductivity. So-called remuneration and additives such as B. Plastics regulate the technical properties.

When differentiating between plasters according to the material, there is usually a differentiation according to the binding agent, as this has a decisive influence on the properties and intended use of the plaster.

The binders are differentiated as follows: minerally bound plasters and organically bound plasters . Mineral plasters have inorganic binders, particularly often lime , cement , gypsum , clay or silicate (water glass), especially in traditional and / or ecological construction methods. Lime and cement are often mixed in order to improve the processing properties. Organically bound plasters have organic binders such as synthetic resins (dispersion), possibly with proportions of silicone resin, acrylates, etc. a.

Executing craftsmen

The craftsman who processes the plaster is the plasterer , plasterer or plasterer, regionally also the whitewater , bricklayer , rabitzer, plisterer or ibser. The plastering of top coatings such as rough or rolled plaster is now also carried out by the painter . In genealogies, the old occupation of rougher and rougher master occurs more often.

Standards and guidelines

  • DIN EN 18 299 VOB - Part C: General technical contract conditions for construction work (ATV)
  • DIN 18350: plastering and stucco work
  • DIN EN 13914-1-2: plastering and stucco work
  • DIN V 18550: 2005-04 Plaster and plaster systems - Execution
  • DIN EN 18 555 plaster
  • DIN EN 18 557 factory mortar
  • DIN 18345 thermal insulation composite systems

literature

  • Technical manual: Plaster - Stucco - Dry construction - Thermal insulation , 3rd edition 2010, Association of plasterers for interior work and facades and the Swiss Association of Painters and Plasterers (SMGV)
  • Hans Albrecht Gasch; Gerhard Glaser; Chamber of Crafts in Leipzig (ed.): Historical plasters: materials and technologies . Sandstein Verlag, Dresden 2011, ISBN 978-3-942422-52-9
  • Annette Spiro , Hartmut Göhler, Pinar Gönül (eds.): About plaster, developing and realizing surfaces . gta Verlag, Zurich 2012, ISBN 978-3-85676-301-5
  • Plaster. In: Meyers Großes Konversations-Lexikon, Volume 16. Leipzig 1908, p. 470.

Web links

Commons : Putz (building material)  - album with pictures, videos and audio files

Individual evidence

  1. ↑ Dietrich Neumann et al. (Ed.): Frick / Knöll Baubauslehre 2, Springer, Wiesbaden 2003, pp. 643–716.
  2. ↑ a b c Dipl.-Ing. (FH) Architecture M.Sc. Bettina Lietz: Fine plasters and stone plasters - Material-colored designs on plaster facades of the 19th and 20th centuries with colored dry mortar - Development of economical and substance-conserving preservation technologies , p. 13ff, final report project no. Az 26503-45, Potsdam University of Applied Sciences, IBB FHP: -> Institute for Building Research and Building Preservation
  3. ↑ Example of coarse barley plaster on the Lauterbach fortified church  ( page no longer available , search in web archives ) (PDF; 217 kB) in the Ore Mountains@1@ 2Template: Toter Link / www.hydroment.de
  4. ↑ materialarchiv.ch
  5. ↑ Pictorial representation as well as a short overview of the plaster structures customary in the respective architectural epochs by the architectural monument preservation office, accessed in February 2016
  6. ↑ Helmut Kollmann: Plaster mortar for specific applications - the interaction of binders, aggregates and additives  ( page no longer available , search in web archives ), March 5, 2009; accessed in February 2017@1@ 2Template: Toter Link / lehrerfortbildung-bw.de
  7. ↑ Technical data sheet of a fiber-containing universal plaster, which is also called adhesive, renovation and thin-layer plaster by the manufacturer.