30 August 2022
Cement plaster finish is an approach by which rough surfaces of wall or roofs for ceilings is altered or turned to give a smooth appearance. In the beginning, the wet material is spread across the bricks or blocks, and afterward, the appropriate equipment is utilized to smooth the surface and level. The primary goal of plastering is to create hard and smooth surfaces that are able to be painted and give a nice aesthetic appeal.
The walls of contemporary homes are finished using blocks, bricks, or attractive stones that show stunning appearances. Materials that are wet and spread across the roof or wall surfaces must not exceed 0.3 centimeters. There are some surfaces with irregularities greater than 3cm. In this situation, under coat, which is a cheap coarse grain, is applied to smooth the surface. This is followed by a finishing coat, which is a thin layer made of fine-grain materials. Furthermore, walls made from stone that is irregular in size and shape may require three coats. The reason for this is that thick undercoats can be sagging due to the weight of wet and heavy plaster. This is the reason why spreading a thin layer and allowing it to dry, followed by applying another undercoat, is the ideal method, as illustrated in Figure 1. Finally, a finish coat is applied to the entire surface.
Types of Plasters based on Materials used
The Lime mixture is made up of line and sand, which is mixed with 1 sand to 3 lime volume. It is not just used as an undercoat but also as a finishing coat. Lime plaster can shrink after drying, so animal hair that is about 5 kg is utilized for 1 millimeter 2 to stop lime plaster from to avoid shrinking and cracking. Lime plaster is a good choice to protect structures from decay and rehabilitation.
The grey dust Portland cement mixes with water using the ratio of 1cement and 3 to 4 washed clean sand in volume to create an undercoat for a solid background like brick blocks, partitions, and walls. The mix of cement and sand may be plastic and will require skilled and experienced labor. Therefore lime or plasticizer is included in the mix, usually with a volume ratio of 1cement:0.25 lime:3 sand, or 1 cement to 4 sand, with a plasticizer. The liquid, called plasticizer, can be added to the mix to help spread the plaster on the surface.
Gypsum plaster is widely used and is a plaster material that can be extracted naturally or manufactured as an end product. This is why it is an important gypsum product used as a finishing coat, undercoat, or to replace with cement and lime in general. Additionally, a small expansion of gypsum can be considered significant and is a good way to avoid shrinkage and cracks. There is a variety of gypsum that is made by heating gypsum up to a certain degree. For instance, anhydrous gypsum is produced by heating gypsum until 170C. O The hemihydrates are gypsum hemihydrates made by heating gypsum higher than 170 C O . Additionally, based on applications for ceilings and walls, Gypsum plasters can be classified as casting, undercoat, finishing one coat, and machine-applied plaster.
Background Plastering Surfaces
The kind of plaster used and the way it is applied varies based on the ceiling or wall which is to get plastered. Blocks or bricks that have solid and rough surfaces have an adhesive mechanism that is mechanical after the plaster has been applied ceiling or walls. The mechanical keys that adhere to the hardened surfaces are created when the spread of dry undercoat plaster has dried. Plaster keys reduce or stop shrinkage of the cement, which is the main component of undercoat plaster. Machine-pressed bricks with great density and smooth surfaces suck up the right amount of water which helps in adhering plasters to surfaces. The amount of water absorption by large smooth surfaces bricks that help in the adhesion of plasters is known as suction. Blocks created by lightweight concrete have huge suctions which prevent the attachment of plaster to the surfaces correctly. This is why it is recommended to reduce the absorption of water by using liquid primers or spraying water prior to laying down. There are two options for surfaces with poor suction. These are PVA bonding agents as well as an agent for bonding polymers. In the first method, the PVA is applied to the surface, and the plaster is sprayed over it while the PVA remains sticky, forming bonds. In the second method, surfaces are treated using a combination of silica sand and polymer, which creates a bond. The glue is created through silica sand particles when the polymer has dried. There are many kinds of galvanized steel beads as well as stops that are made for use in the plasterboard and plaster to reinforce stop angles and angles. They are employed in the connection of plaster from ceiling to wall as well as plaster to other materials. Galvanized steel is used as stops to provide perfect finishes on plaster joints and other materials at angles around doors and windows and skirting, as shown in Figure 2.
Plaster Finishes Timber Joists and Studs
Plaster spreading over timber lath is a traditional and old technique used to give an even surface for the ceilings and floors of the timber floor and partitions made of studs. This method is, to a great extent is, has been replaced by gypsum plasterboard, which is the reason further details are not included. Gypsum plasterboard is composed of hard gypsum and bonds to two heavy pieces of paper to prevent any damage that may result from handling and installation of Gypsum plaster. It is made in different sizes, such as 0.95 centimeters, 1.25 millimeters, 1.5 cm. and 1.9 cm. It is used as dry linings or backgrounds for plaster in various sizes of boards. Gypsum plasterboard is extensively used in ceilings of floors made of timber and roofs to create lines. Plasterboard is extremely cost-effective and can be put up and then plastered in minutes. Another benefit is that it is not susceptible to fire since it's non-combustible. However, inadequate sound insulation, vibration cracks, or movement are disadvantages of the plasterboards.
Skating and Architraves
Skirts are a narrow band that is positioned around the wall's base at the intersection of floor and wall and made strong enough to be able to withstand the force of a hit. They are used to highlight the floors and walls. There are many kinds of skirting, including tiles, timber, tile, and magnetite. Architraves are forms or molds that are employed to decorate windows and doors.
Types of plaster finishes utilized for Building Construction are:
Different kinds of finishes for plaster that have different looks are available.
Sand finished face
Pebble dash finish
Smooth Cast Finish on Plaster
To achieve a smooth finish on the cast For a smooth cast finish, the mortar used should be 1:3 (sand: cement). Fine Sand is recommended to make the mortar. To spread the mortar, skimming floats or wood floats is the best tool. This ensures a level and smooth surface is achieved.
The Rough Cast Finish
The roughcast finish can also be known as the spatter dash finish. The mortar used to make roughcast finish is made up of coarse aggregates, along with cement as well as sand. The ratio is approximately 1. 1.5 to 3. The size of the coarse aggregate is from 3mm to 12mm. The majority of the mortar is gathered by trowel, and then mixed into the surface, then made level using a wooden floating. This type of finish is used for exterior renderings.
A Sand-Faced, Plaster-Finished Finish
For a sand-faced finish, Two coats of plastering are needed. In the first coat, a 12mm thick cement sand mortar at a 1:4 ratio is recommended. The first coat is applied in the form of zigzag lines. It is then allowed to cure for 7 days. Then, a thick layer of 8mm of a second coat made up of cement and sand at a 1:1 ratio is put on. The surface is leveled using a sponge. Then, take some sand and screen it for an even grain size. The sand that has been screened is then applied in the second coat by using floating floats that skim or are wooden. Then, a sand-faced finish with a uniform grain size of sand can be obtained.
Pebble Dash Plaster Finish
Pebble Dash Finish requires a mortar of 12mm thickness using sand and cement in a ratio of 1:3. After plastering, pebbles ranging from 10mm to 20mm can be sprayed onto the surface of the plaster. They are then pressed into the surface with a wooden float gradually. When they are hardened, they add an aesthetic look to the building.
Scrapped Plaster Finish
To get a scraped finish, apply a final coat of 6-12 millimeters in thickness. Then allow for it to set. After a few minutes, using a steel blade or plate, scrape the plastered layer to 3 millimeters in depth. The surface that is scraped is less susceptible to cracks.
Demeter Plaster Finish
It is similar to the finish of pebbles. However, in this instance, stones of gravel and flint can be utilized instead of pebbles.
Textured Plaster Finish
Textured finishes are created by the stucco coating in which various textures and designs are created on the final coat with appropriate tools.
External rendering of buildings
The exterior of buildings made of clay blocks or concrete is not thought to be attractive visually and doesn't provide attractive looks. This is why the exterior faces are repainted and changed by applying two or three coats of cement or lime combined with natural aggregates and then smoothed or textured. Furthermore, rendering increases and makes walls more resistant to rain penetration. External rendering is built on a strong bond with the wall's background using combinations and finishing.