Cement plastering is generally applied to give excellent finishing to the inside and outside surface of the wall and also on the ceiling. Plastering work also provides a finished surface over the brickwork that is firm and smooth therefore it enhances the look of the building.
The main purposes of plastering are to protect the surface from climatic impacts, to cover the defective workmanship in brickwork, and to give an excellent surface for paintwork. Cement plaster is normally given in a single layer or double layer. Double layer plaster is suitable where the thickness of plaster is kept over 15 mm or when it is required to provide a really fine finish.
Prepared Surface for Plastering Work
Keep all the mortar joints of the wall rough, in order to sustain a good bonding to maintain plaster.
Use a wire brush to clean all the joints and surfaces of the wall, the wall surface does not have any oil or grease, etc left on the wall surface.
In case the surface is smooth or the plastering wall is old, then remove the mortar joint to a depth of a minimum of 12 mm to give a good quality bonding to the plaster.
If the projection on the wall surface is over 12 mm, then rub it out to maintain a smooth surface of the wall. It will reduce the usage of plaster. For any gaps or holes on the surface, fill it with specific material in advance.
Roughen the entire wall to be plastered.
Wash the mortar joints and complete wall to be plastered, and make it wet for minimum 6 hours before start cement plaster.
GroundWork for Plaster
- To sustain smooth thickness of plastering throughout the wall surface initially fix dots on the wall. A dot comes from the piece of plaster, with dimensions 18 mm x 18 mm and thickness is the same as plaster thickness.
- At first, dots are fixed on the wall horizontally, and then vertically at a spacing of about 2 meters finish the entire wall surface.
- With the help of plumb-bob, check out the verticality of dots, one over the other.
- When the dots are established, the vertical strips of plaster alias screeds are established among the dots. These screeds perform as the gauges for maintaining the proper thickness of plastering.
PROVIDING 1st LAYER
- For brick masonry, the thickness of 1st layer plaster generally keeps 12 mm and for concrete masonry, this thickness varies from 9 mm to 15 mm.
- The ratio of cement and sand for 1st coat plaster differs from 1:3 to 1:5
- By utilizing a trowel, start the 1st layer of plaster among the locations developed with the screeds on the wall surface.
- The surface must be leveled with flat wooden or aluminum floats and wooden or aluminum straight edges.
- After the leveling is finished, leave the 1st layer to set however not to completely dry and after that roughen it with a scratching tool to create scratches because good bonding for the 2nd layer of plaster.
PROVIDING 2ND Layer
The thickness of the second layer or finishing layer may vary from 3mm To 5 mm.
The ratio of cement and sand for 2nd layer plaster varies from 1:3 to 1:6.
Before start, the second layer wet the first layer uniformly.
Provide the finishing layer with wooden or aluminum floats to the best uniform surface and use finishing touch with a steel trowel
Preferably, the finishing layer must be prepared to start from the top towards the bottom and ended up in one proceeding to remove joining marks.
After Completion of Plaster Work
After finishing the plasterwork the most important thing is the cleaning of doors, windows frame, and floor area.
Curing must be started immediately after the plaster has hardened sufficiently and should be cured for at least 7 days.
Curing of Plastering works
After completion of the plastering work, it is maintained wet by spraying water for a minimum of 7 days in order to produce strength and hardness.
Use of gunny bags or other materials is used to keep the plastering works wet in external works. Poor curing may cause cracks development or efflorescence in plasterwork.
Scaffolding for Plastering Work
Suitable steel or wooden scaffolding needs to be provided for the inner wall plaster to meet particular site requirements. When it comes to the outside periphery, it must be required to make double Steel scaffolding, enough strong so as to survive all loads upon it. It must be independent of work and fixed two sets of vertical and inclined supports.
Materials required for Plastering Work
Before start plastering work make sure, how many materials are needed for plastering work such as cement and sand? The quantity of plastering works area is measured in the square meter or square foot. It is measured by multiplying the length and height of the wall surface.
The approximate materials used for 12 mm thickness in the different ratio is as under,
|Area||Plaster thickness||Mix Ratio of Mortar||Cement(Kg)||Sand (Cft)|
|100 sqm||12 mm||1:3||533.40||40.70|
|100 sqm||12 mm||1:4||426.72||42.95|
|100 sqm||12 mm||1:5||355.60||44.70|
|100 sqm||12 mm||1:6||304.80||46.10|