External render

Last updated

An external render is, in its most basic form, a coating applied to the walls of a building, to provide a protective coating which would prevent rain penetration. It also acts as a decorative finish to enhance the appearance of a building.

Contents

History

Rendering is a traditional craft that has evolved over many centuries. Basic rendering began as a method of excluding draughts and rain by using clay to fill in cracks and crevices, referred to as wattle-and-daub. [1] Other renders, based on lime [2] binders were also used over the years. These materials had one significant disadvantage in that they were not very resistant to water.

The introduction of Portland cement [3] meant that durable mortars [4] could be produced and weather resistant renders resulted. Through the years technological advances have aided the development of cutting edge render systems that aim to improve the longevity of a buildings structural capacity. [5]

Manufacture and production

Traditionally, a render would be manufactured on site by a plasterer mixing sand, cement and sometimes lime material together with water to produce his render. This would then be applied to the walls, usually in either two or three coats. [6]

When painting, there is usually a primer, an undercoat and a topcoat. Similarly in renders there may be a stipple coat, then an undercoat (sometimes called a base coat) and finally a final coat (sometimes called a topcoat). The difference is that in renders, the final thickness is 15 mm. [7]

Development of a site mixed render is the factory made render. All the render ingredients are dry blended together in a modern factory, creating a powdered product which can be supplied in bags. When the product is delivered to site the plasterer just needs to mix the product with water and apply it to the wall.

The factory made render has an advantage over the site mixed render in that the composition of the render and all the raw materials are closely controlled and accurately measured. [8] Supplying a render in this way allows the manufacturer to include performance enhancing additives into the formulation. Whilst many site mixed renders are subsequently painted, factory made renders can be supplied as a wide variety of self-coloured products, eliminating the additional expense of painting.

Application

There are two main methods of applying render, by hawk and trowel or by machine. In the hawk and trowel method the product is first mixed with water to a workable paste and then the plasterer applies the wet paste render to the wall and levels it off, using a hawk and trowel. Machine applied renders are usually factory made products. The machine is essentially a mixing pump which mixes the product with water and pumps the paste to a nozzle which sprays it onto the wall. The wet paste is than levelled off. Application of render using a machine is usually a much faster operation than by hand, meaning that larger areas can be rendered during a working day. The application of render has to be completed in the correct weather conditions. If the temperature is too low, moisture can be trapped within the render. If the temperature is too high, the render will dry out too quickly, leading to the formation of cracks.

Related Research Articles

Concrete Composite construction material

Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminum combined. Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $600 billion in revenue by 2025. This widespread use results in a number of environmental impacts. Most notably, the production process for cement produces large volumes of greenhouse gas emissions, leading to net 8% of global emissions. Other environmental concerns include widespread illegal sand mining, impacts on the surrounding environment such as increased surface runoff or urban heat island effect, and potential public health implications from toxic ingredients. Significant research and development is being done to try to reduce the emissions or make concrete a source of carbon sequestration, and increase recycled and secondary raw materials content into the mix to achieve a circular economy. Concrete is expected to be a key material for structures resilient to climate disasters, as well as a solution to mitigate the pollution of other industries, capturing wastes such as coal fly ash or bauxite tailings and residue.

Mortar (masonry) Workable paste which hardens to bind building blocks

Mortar is a workable paste which hardens to bind building blocks such as stones, bricks, and concrete masonry units, to fill and seal the irregular gaps between them, spread the weight of them evenly, and sometimes to add decorative colors or patterns to masonry walls. In its broadest sense, mortar includes pitch, asphalt, and soft mud or clay, as used between mud bricks. The word "mortar" comes from Old French mortier, "builder's mortar, plaster; bowl for mixing." (13c.).

Plaster Broad range of building and sculpture materials

Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "render" commonly refers to external applications. Another imprecise term used for the material is stucco, which is also often used for plasterwork that is worked in some way to produce relief decoration, rather than flat surfaces.

Grout Building material

Grout is a dense fluid which is used to fill gaps or used as reinforcement in existing structures. Grout is generally a mixture of water, cement and sand, and is employed in pressure grouting, embedding rebar in masonry walls, connecting sections of pre-cast concrete, filling voids, and sealing joints such as those between tiles. Common uses for grout in the household include filling in tiles of shower floors and kitchen tiles. It is often color tinted when it has to be kept visible and sometimes includes fine gravel when being used to fill large spaces. Unlike other structural pastes such as plaster or joint compound, correctly mixed and applied grout forms a water resistant seal.

Building material Material which is used for construction purposes

Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, wood, and even twigs and leaves, have been used to construct buildings. Apart from naturally occurring materials, many man-made products are in use, some more and some less synthetic. The manufacturing of building materials is an established industry in many countries and the use of these materials is typically segmented into specific specialty trades, such as carpentry, insulation, plumbing, and roofing work. They provide the make-up of habitats and structures including homes.

Stucco Construction material made of aggregates, a binder, and water

Stucco or render is a construction material made of aggregates, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and artistic material in architecture. Stucco can be applied on construction materials such as metal, expanded metal lath, concrete, cinder block, or clay brick and adobe for decorative and structural purposes.

Lath and plaster Finish mainly for interior dividing walls and ceilings

Lath and plaster is a building process used to finish mainly interior dividing walls and ceilings. It consists of narrow strips of wood (laths) which are nailed horizontally across the wall studs or ceiling joists and then coated in plaster. The technique derives from an earlier, more primitive, process called wattle and daub.

This page is a list of construction topics.

Natural building

A natural building involves a range of building systems and materials that place major emphasis on sustainability. Ways of achieving sustainability through natural building focus on durability and the use of minimally processed, plentiful or renewable resources, as well as those that, while recycled or salvaged, produce healthy living environments and maintain indoor air quality. Natural building tends to rely on human labor, more than technology. As Michael G. Smith observes, it depends on "local ecology, geology and climate; on the character of the particular building site, and on the needs and personalities of the builders and users."

Lime (material) Calcium mineral

Lime is a calcium-containing inorganic mineral composed primarily of oxides, and hydroxide, usually calcium oxide and/or calcium hydroxide. It is also the name for calcium oxide which occurs as a product of coal-seam fires and in altered limestone xenoliths in volcanic ejecta. The International Mineralogical Association recognizes lime as a mineral with the chemical formula of CaO. The word lime originates with its earliest use as building mortar and has the sense of sticking or adhering.

Lime plaster

Lime plaster is a type of plaster composed of sand, water, and lime, usually non-hydraulic hydrated lime. Ancient lime plaster often contained horse hair for reinforcement and pozzolan additives to reduce the working time.

Autoclaved aerated concrete Lightweight, precast building material

Autoclaved aerated concrete (AAC) is a lightweight, precast, foam concrete building material suitable for producing concrete masonry unit like blocks. Composed of quartz sand, calcined gypsum, lime, cement, water and aluminum powder, AAC products are cured under heat and pressure in an autoclave. Invented in the mid-1920s, AAC simultaneously provides structure, insulation, and fire- and mold-resistance. Forms include blocks, wall panels, floor and roof panels, cladding (façade) panels and lintels.

Plasterwork Construction or ornamentation done in plaster or a similar material

Plasterwork is construction or ornamentation done with plaster, such as a layer of plaster on an interior or exterior wall structure, or plaster decorative moldings on ceilings or walls. This is also sometimes called pargeting. The process of creating plasterwork, called plastering or rendering, has been used in building construction for centuries. For the art history of three-dimensional plaster, see stucco.

Plasterer

A plasterer is a tradesman who works with plaster, such as forming a layer of plaster on an interior wall or plaster decorative moldings on ceilings or walls. The process of creating plasterwork, called plastering, has been used in building construction for centuries. A plasterer is someone who does a full 4 or 2 years apprenticeship to be fully qualified

Lime mortar Building material

Lime mortar or torching is composed of lime and an aggregate such as sand, mixed with water. The ancient Indians were the first to use lime mortars, which they used to plaster the Temples. In addition, the Egyptians also incorporated various limes into their religious temples as well as their homes. Indian traditional structures built with lime mortar, which are more than 4,000 years old like Mohenjo-daro is still a heritage monument of Indus valley civilization in Pakistan. It is one of the oldest known types of mortar also used in ancient Rome and Greece, when it largely replaced the clay and gypsum mortars common to ancient Egyptian construction.

Joint compound A paste of gypsum powder and water that fills seams around sheets of drywall

Joint compound is a white powder of primarily gypsum dust mixed with water to form a paste the consistency of cake frosting, which is used with paper or fiber joint tape to seal joints between sheets of drywall to create a seamless base for paint on interior walls and ceilings. It is often referred to simply as mud or as joint cement.

Earthen plaster is a blend of clay, fine aggregate, and fiber. Other common additives include pigments, lime, casein, prickly pear cactus juice (Opuntia), manure, and linseed oil. Earthen plaster is usually applied to masonry, cob, or straw bale interiors or exteriors as a wall finish. It provides protection to the structural and insulating building components as well as texture and color.

External wall insulation

An external wall insulation system is a thermally insulated, protective, decorative exterior cladding procedure involving the use of expanded polystyrene, mineral wool, polyurethane foam or phenolic foam, topped off with a reinforced cement based, mineral or synthetic finish and plaster.

Cement render Mortar mix of sand and cement for wall application

Cement rendering is the application of a mortar mix of sand and cement, and water to brick, concrete, stone, or mud brick. It is often textured, colored, or painted after application. It is generally used on exterior walls but can be used to feature an interior wall. Depending on the 'look' required, rendering can be fine or coarse, textured or smooth, natural or colored, pigmented or painted.

Wattle and daub Building technique using woven wooden supports packed with clay or mud

Wattle and daub is a composite building method used for making walls and buildings, in which a woven lattice of wooden strips called wattle is daubed with a sticky material usually made of some combination of wet soil, clay, sand, animal dung and straw. Wattle and daub has been used for at least 6,000 years and is still an important construction method in many parts of the world. Many historic buildings include wattle and daub construction.

References

  1. ↑ Prichett, Ian. "Wattle and Daub". www.buildingconservation.com. The Building Conservation Directory.
  2. ↑ Holmes, Stafford. "An Introduction to Building Limes". www.buildinglimesforum.org.
  3. ↑ Reid, Henry (1877). The Science and Art of the Manufacture of Portland Cement with observations on some of its constructive Applications. London.
  4. ↑ "Factory produces lime: sand mortar for masonry" (PDF). www.mortar.org.uk.
  5. ↑ "Silicone Technology". www.k-rend.co.uk.
  6. ↑ Snell, David (August 2012). "How to..two-coat render a wall". The Telegraph. The Telegraph Media Group. The Telegraph.
  7. ↑ "Paints and Renders explained". www.self-build.co.uk.
  8. ↑ "Factory produced mortar for External Rendering" (PDF). www.mortar.org.uk.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.