Plastering is the process through which rough surfaces of wall and ceiling roofing are altered or twisted or rendered to give smoothness. In the beginning, wet materials are sprayed over the bricks or blocks before the proper equipment is employed to smooth the surface even. The main reason for plastering is to create a hard and smooth surfaces that can be painted, and give nice aesthetic appeal.
In recent times, walls in contemporary homes are decorated with blocks or bricks or attractive stones that show stunning appearances. The amount of water that is spread across walls or roofs should not exceed 0.3 centimeters. There are some surfaces with irregularities greater than 3cm. In this situation, under coat, which is a inexpensive coarse grain materials is utilized to smooth the surface. This is followed by a finishing coat, which is a thin layer of fine grain material. Additionally, walls made of stone that is irregular in size and shape could require three coats. This is due to the fact that the thicker coats tend to slide due to the weight of wet and heavy plaster. This is the reason why spreading a thin layers and allowing to dry followed by applying another under coat is the most effective method. Then, the finish coat is applied to the entire surface.
Plaster types are based on the material used
Lime Plaster
Lime mixture is made up of line and sand which is mixed with 1 sand for 3 lime in volume. This mixture is not only utilized for under coats but it is also used as a finishing coat. Lime plaster can shrinking after drying, so animals hair that is about 5 kilos is used in 1 m2 of area to stop the lime plaster from cracking and shrinking. Lime plaster is a good choice to restore structures from the past and rehabilitation.
Cement Plaster
The grey white powder Portland cement mixes with water in the ratio of 1 cement and 3 to 4 clean washed sand in volume to create an undercoat for a solid background like brick blocks and partitions. Mixture of cement and sand may be plastic, and will require expertise and experience. Therefore, lime or plasticizer are typically added to the mixture in a volume ratios of 1cement:0.25 lime:3 sand or 1 cement for 4 sand using plasticizer. The liquid called plasticizer is can be added to the mix to make it easier for the plaster to spread on the surface.
Gypsum Plaster
Gypsum plaster is a widely-used and is a plaster material that can be mined naturally or made as an by-product. Therefore, it is a crucial gypsum material used as an undercoat, finish coat, or to replace with cement and lime in general. Furthermore, the slight expansion of gypsum can be considered important to prevent shrinkage and cracks. There are a variety of gypsum which are made by heating gypsum to certain degree, for instance anhydrous gypsum that is produced by heating gypsum to 170 Co. Similarly, hemihydrates are created by heating gypsum greater than 170Co. Additionally, based on the use for ceilings and walls, the gypsum plasters are classified by type, such as casting, undercoat, finishing one coat and machine-applied plaster.
Background Surfaces for Plaster
The type of plaster and the method of application differs based on the the ceiling or wall which is to be plastered. Blocks or bricks that have solid and rough surfaces have the ability to adhere mechanically when plaster is sprayed on the ceiling or walls. Mechanical keys that stick the hardened plaster to the walls or ceilings are created when the spread of subcoat plaster that is wet has been dried. Plaster keys restrict or limit shrinkage in the cement that is the main component of undercoat plaster. Machine-pressed bricks that have large density and smooth surfaces absorb the right quantity of water to aid in adhering the plasters to surfaces. The amount of absorption by the large smooth surfaces bricks that aid in adhesion of plaster is known as suction. Blocks created by lightweight concrete have huge suctions that hinder the adhesion of plasters on surfaces correctly. This is why it is recommended to reduce the absorption of water by using liquid primer or spraying water prior to exterior plastering in Auckland. There are two options for surfaces that have low suction. They are PVA bonding agent as well as an agent for bonding polymers. In the first method it is the case that polyvinyl acetate gets applied to the surface, and then the plaster is spread over as long as the PVA remains sticky, forming a bonds. In the second method, surfaces are treated using a combination of silica sand and the polymer while the bonding is formed by the silica sand grains after drying the polymer. There are a variety made of galvanized steel beads as well as stops, which are manufactured to be used using plaster and board as stop and angle reinforcement. They are employed in the connection of plaster to ceiling and also to join other materials. Galvanized steel is used as a stop to provide perfect finishes on the joints of plaster with another material at angles around windows and doors and around skirting.
Plaster Finishes to Timber Joists and Studs
Plaster spreading over timber lath is a traditional and old method used to provide a an even surface for the timber floors, ceilings, or stud partitions. This technique is to a vast extent was replaced by gypsum plasterboard which is the reason why more details are not offered. Gypsum plasterboard is composed of gypsum that is hard and bonds to two heavy paper which protect against damage resulting from handling and installation of Gypsum plaster. It is produced with different thicknesses like 0.95 millimeters 1.25 millimetres 1.5 cm. and 1.9 cm. It is used as dry linings or background for plaster in various sizes boards. Gypsum plaster board is extensively used for ceilings, floors and roofs for coverings. Plasterboard is extremely cost-effective and is able to be installed and plastered quickly. Another advantage is that it is not susceptible to fire as it is not combustible. But, low sound insulation, cracks that vibrate or move are the main drawbacks to plaster boards.
Skirting and Architraves
Skirts are a narrow strip of fabric that is placed around the wall’s base at the an intersection between floor and wall. They are designed to be strong enough to withstand the force of a hit. They help to draw attention to the flooring and wall junctions. There are a variety of skirting like wood, metal tiles, magnesite and tile. Architraves are moulds or forms that are utilized to create a decorative look around windows and doors.
The types of plaster finishes employed to construct Building Construction are:
Different kinds of finishes for plaster with various appearances are available.
Smooth, smooth cast finish
Rough-cast finish
Sand surfaced finish
Pebble dash finish
Scraped finish
Depeter finish
Textured finish
Smooth Cast Plaster Finish
For a smooth, polished finish For a smooth cast finish, the mortar used should be of the ratio 1:3. Fine Sand should be used to make the mortar. To spread the mortar, the skimming float, or the wood float is the best tool. Thus, a smooth and level surface can be achieved.
Rough Cast Plaster Finish
Rough cast finish can also be referred to as spatter diesh finish. Mortar used to make rough cast finish is composed of fine aggregates, along with cement, sand and. Their ratio is approximately 1. 1.5 x 3. The dimension of coarse aggregate used is from 3mm to 12mm. The majority of the mortar is taken up by trowels and then dumped into the floor and then levelled with a wooden floating. This type of finish is preferred for exterior renderings.
Sand Faced Plaster Finish
To achieve a sand faced finish 2 coats of plastering are needed. The first coat should be 12mm thick cement sand mortar at the ratio 1:4 is recommended. The first coat must be applied in the form of zigzag lines. Then it’s allowed to cure for 7 days. Then an 8mm thick layer of the second coat, which is made of cement and sand in a 1:1 ratio is put on. Smooth the surface with a sponge. Take sand, then screening it to achieve a an even grain size. The sand that has been screened is then applied to the second coat by using a floating floats that skim or wooden. Then, a sand-faced finish with a uniform grain size of sand is achieved.
Pebble Dash Plaster Finish
Pebble Dash Finish requires a the application of a 12mm thick mortar using sand and cement in a ratio of 1:3. After the plastering process, pebbles ranging from 10mm to 20mm are tossed onto the surface that has been plastered. After that, they are pressed into the surface of the plaster using wooden floats gradually. After they have hardened, they give an attractive design to your structure.
Scrapped Plaster Finish
To get a scrapped finish, apply the final coat of 6-12 millimeter thickness. Allow the dry. After a while, using a steel blades or plates, you can scrap the plastered layer to 3mm in depth. The surface that is scraped is less susceptible to cracks.
Depeter Plaster Finish
This is also like the finish of pebbles. However, in this instance, gravel pieces or flints can be used instead of pebbles.
Textured Plaster Finish
Textured finish comes from the stucco plastering process in which various textures or designs are applied to the final coat by using appropriate tools.
External Rendering of Buildings
Generally speaking, the exteriors of structures made from clay blocks or concrete are not believed to be attractive visually, and they do not offer attractive looks. That’s why the exterior faces are altered and rendered with three or two layers of cement or lime combined with natural aggregates and then smoothed or textured. Furthermore, rendering increases and improves wall resistance to the penetration of rain. Additionally, exterior rendering relies on strong bonds between the backdrop, used combinations, and finishing.
