Cement Plastering Plastering not only makes the surfaces smooth but also creates a good finishing to the walls, ceiling and roofs. GharExpert provides you details about the material requirement for Cement plastering, Advantages and disadvantages of Cement plaster, Precautions for Cement plaster, Cement plaster inspection checklists, Preparation for Cement plaster, Tips for Cement plaster, etc Plastering Plastering is the term used to describe the material spread over the surface of irregular and coarse textured wall, column, and ceiling to provide a smooth, hard and leveled finish which can be painted for good appearance. In actual ‘Plastering’ is an art, truly recognized for constructing the base. It refers to the construction done with plaster which includes a layer of plaster on an interior wall or plaster decorative moldings done on ceilings or walls. The process of creating plasterwork is called ‘Plastering’. It’s a unique skill to plaster the wall, level it and achieve a good and even finishing. Plasterboard is to form the sub-base for ceilings, partition walls. An adequate and rigid frame made up of timber battens is needed for it. Fix runner boards made from spare lengths to harden the ceiling side by side. It will provide ease of access in the roof void and will be supporting for electrical cables.
1.) Minimize the defects in ‘Plaster Work’
Tips to minimize the defects in ‘Plaster Work’ are given below.
Carry ‘Plastering’ out with skilled mason. Maintain the bond of brick works properly. Remove the efflorescence of the brick by rubbing brushes on the surface and wash them with clean water. Use the bricks of superior quality. Make the water water used for ‘Plastering’ free from salt. Plaster the surface with enough water so that it may not absorb water from the plaster. Avoid excessive troweling. Provide Damp proof course at convent place in the building. Close pot holes with wet brick bets and mortar before starting the plaster. Make square or rectangular form of the patch if any patch is to be repaired.
Also keep in mind the points mentioned below before Plastering
Make sure to fix any leakages or moisture before plastering. Ensure that the walls are completely dry at least 24 hours before plastering. Also keep the room at 55 to 70 degrees temperature during plastering or till the plaster sets completely. Wear safe clothes- a long sleeve shirt and cotton gloves for skin protection.
2.) Cracks at the junctions of Brick Walls and RCC slabs
According to the designs/drawings there is change in the material on which plaster is to be done such as brick surface, RCC surface etc.
Avoid cracks in case of discontinuity of material (different types of material). Apply a neat cut through the plaster at the junction to prevent cracking of plaster caused by discontinuity of backing, changing from concrete to brick work or changing from wall to ceiling. Make the cut through the plaster not deeper than 6 mm while the plaster is still green (at the finishing of plaster) to keep the wall plaster separate from ceiling plaster.
3.) Achieve a good quality in ‘Plastering’
Some precautions for good Plastering are given below.
Fix all the fittings of electric pipes, water supply pipes, and electric boxes etc. properly as per drawing /requirement before starting the plaster work. Fit all the pipes so deep into the walls that the pipes can get proper thickness of mortar on them to avoid cracks in plaster surface. Make proper bond between the background and the plaster coat. Make surface of the wall clean, free from all racked mortar and dust etc. with the help of iron brushes. Wash and water the surface for 24 hours before the plaster is applied.
Fix the reference mark (BUNDAS) on the walls truly in lines and plumb before starting the plaster. Ensure that all the edges of openings are round. Check the plaster frequently with straight edges and plumb bob. Do proper curing for at least 15 days to harden the plaster sufficiently and avoid the damage when watered. Mark proper dates on the plastered surface for proper curing. Protect all the fittings on the wall. Clean any splash of mortar on a finished surface immediately on completion of the work.
4.) Ratio of Cement and Sand for ‘Plastering’
The ratio of cement and sand for plastering is given below.
6 MM thickness of cement plaster and cement mortar 1:3 or 1:4 is recommended for cement plastering on RCC surfaces, on the RCC walls, Fascia etc. or as directed by the Engineer, 6 MM to 10 MM thickness of cement plaster and cement mortar in 1:3 or 1:4 ratios is recommended for underside of RCC slabs. 12 MM thick cement mortar in 1:4 ratios is recommended on the walls where smooth side exists.
Either 9 or 4.5 MM thick and 15 MM thick cement plaster in 1:4 ratios is recommended on the rough side of the walls. 20 MM thick cement mortar in 1:3 with two coats is recommended in case of vertical Damp Proof Course (DPC). 6 MM thick cement mortar in 1:3 with a coat of white washing is recommended in case of bearing plaster on the walls under the slab. 15 MM thick cement mortar in 1:3 is used with 3 MM thick cement rendering on plaster in case of Dado.
5.) Raw Materials and Scaffolding for ‘Plastering’
Raw materials and scaffolding required for plastering are given below.
Cement, sand and water are the raw materials required for plastering. Double scaffolding independent of the work having two sets of vertical supports shall be provided for all exposed plaster work. Single scaffolding shall be permitted for all other plaster work in building.
6.) Specification of ‘Plastering’
Here is the specification of plastering.
‘Plastering’ is the finishing coat which provides a good lo ok and improves hygienic conditions in the building. Before starting the plaster reference marks (BUNDAS) should be made on the wall in 2” to 3” dia. Plastering is done with cement and sand mortar. It consists of different thickness as per requirement of the site. Plastering is done by applying cement mortar with required ratio i. e. 1:3, 1:4, 1:6 on the walls and the plaster should be in straight line, level and plumb and the joint must be in right angle. The surface to be plastered should be racked out and cleaned with wire brush. It should be made wet 24 hours before starting the plaster. All the doors, window frames, electric fittings and water supply lines must be fitted before starting the plaster and they should be laid as per drawings. Care should be taken that unwanted cement mortar on the frames and electric fittings should be cleaned immediately after finishing the plaster. Proper curing should be done at least for 7 days after the plastering is complete as it is the most important factor for maintaining the strength of plaster.
7.) Recommended thickness of 'Cement Plaster'
The recommended thickness of cement plastering is given below.
Recommended thickness of plastering for brick walls is 12 MM, 15 MM or 20 MM. 12 MM thick cement plaster is done where the plain surface of brick masonry is plastered. 15 MM cement plaster is required on the rough side of 9” and 4.5” wall. 20 MM thick cement plaster is done in two coats in some cases on rough side of wall or according to the design requirement. 18 MM thick cement plaster with neat cement slurry is required for making ‘Dado’ with the cement concrete flooring. Recommended thickness of plastering for RCC surface is 6 MM and 10 MM. 6 MM thick cement plaster is done on the RCC surface where it is required. 10 MM thick cement plaster is done underside of the RCC ceiling/ roof.
8.) Time schedule for Cement Plastering
Time schedule for cement plastering is following.
Plan the plastering when the surface receiving plaster coat is sufficiently matured. Ensure that subsequent building operations do not cause any damage in plaster work. Start external plastering from the top most floors and proceed downwards. Start internal plastering after the structural work is complete. Do plastering on ceiling wherever required before the walls are plastered.
9.) Tools required for Plaster Work
1. 2. 3. 4. 5. 6. 7. 8. 9.
‘Soot Gola’ (Thread) Racking tools Wire Brush Laying Trowel Straight Edge Brick Hammer Plumb Water Level Wooden setting out Square
10.) Which are different types of plastering for construction work?
1. Sand faced p laster:
The first coat of sand faced cement plaster is done with cement mortar in 1:4 with coarse sand after curing the plaster for seven days the second coat of cement plaster 1:3 ratio will be done on the first coat.
Sponge is used in the second coat and it is applied when the second coat is wet, it is thus worked that the density of sand grain appear on surface is equal and uniform. The surface is kept well watered at least for 15 days.
2. Roug h Cast Plaster:
This plaster is a mixture of sand and gravel in specified proportion dashed over a freshly plastered surface. The plaster base consists of two coats, under layer 12 mm thick and top layer 10 mm thick having the cement mortar ratio 1:3. In order to make the base more plastic, about 10% of hydrated lime by volume of cement shall be added while prepare mortar.
3. Pebbled dash p laster:
It is similar to rough cast finish except clean pebble of size from 6 mm to 12.5 mm are dashed against the surface so that there are laid in position by mortar applied already.
4 . Sm o o t h c a s t p l a s t e r o r p l a i n f a c e p l a s t er :
This finish is just similar to sand faced finish except fine grained sand is used instead of coarse sand. No sponging is done to expose the sand grain. It is normally done on internal walls.
5. De peter Plaster:
This is just another form of rough cast finish. The rendering coat of 12 mm thick is prepared as in case of pebbled dash finish. While this coat is wet, pieces of gravel are pressed with hand on the surface. Thus it is possible to have beautiful patterns and ornamental designs on the surface by selecting materials of different colors.
6. Washed s ton e Grit Plaster:
This plaster is done in two layers; under layer 12 mm cement plaster in 1: 4 ratios. This is furrowing the under layer with scratching tools applying cement slurry on the under layer at the rate 2 Kg. cement per SQM and on the top layer 1d5 mm cement plaster 1:0.5: 2 ( 1 cement : 0.5 coarse sand : 2 stone chipping 10 MM nominal size. ) in panels with groove all around as per approved pattern including washing the top layer with brushes and water to expose the stone chipping .
7 . P l as t e r i n g w i t h t e r r a z zo f i n i s h :
This plastering is normally 18 mm --------- with Terrazzo finish, rubbed and polished under layer 12mm thick plaster 1:3 and top of 6 mm thick white, black, chocolate l, gray ,
yellow or green marble chips of 3 mm laid in cement marble powder mix 3:1 by weight in proportion 4:7 marble powder mix cement 4 : 7 marble chips . 8 . Ex t e r n a l w a l l c l a d d i n g b y s t o n e :
This plastering is normally done by Dholpur stone.
