Plastering is a layer of cement mortar that protects the structure from external Agencies like rain, sun, storm or improve the impermeability of structure and also give the aesthetic appearance to the structure. For the internal area a 10 mm thick layer is applied and for the external area, we applied 12mm thickness plaster.
Important term used in plaster
Cement slurry:-A cement slurry is a mixture of cement, sand, and water in suitable proportion and desired consistency and it also works as a paste of bonding agent
Hacking:-Making an indent of the control size above the concrete surface is called hacking, so that plaster can make good bonding with the concrete surface like a beam, column, ceiling roof and stairs etc.
Button marking:-Button marking is a process by which we can make plastering of the entire structure in level.
SBR:- (styrene-butadiene rubber) :- SBR based liquid polymer an additive which when used with sand/cement composites, greatly increases the resistance to water penetration, and improves the abrasion resistance and durability ( ex: E 135 Ardex Endura product)
Expanded metal mesh fixing:- Every material has a different coefficient of thermal expansion due to which Cracks develop at the junction of Block Work and Concrete Surface, To fix these cracks, we fix a metal mesh at the junction so that the tensile strength of the plaster increase and chances of cracks reduced
Procedure of plastering
The structure should be left for some time so that the extent to which the structure is to be expanded and contracted
- Before plastering, cured well and dry the surface
- Button marking should be done to make sure that our plaster is at the level
- The hacking process should be completed and the size of the hacking indent is 2.5 cm in length and 2 or 3 mm in depth.
- Fixed the expanded metal mesh at the junction of two different material like the junction of block and concrete, junction of electric pipe with blocks. Then applied cement mortar paste and cured for 3 days
- All cutouts of the electric box should be properly covered because if the mortar Enter such as opening the conduit may get damaged
- LDPE sheet should be spread below the surface to be plastered so that the plastering mortar that falls from above can be used again.
- Batch box and Ms sheet should be available for the measurement and mixing of mortar
- The required quantity of sand is placed on the Ms sheet and the required quantity of cement is placed and mix using the spade
- Ceiling plaster should be done first
- Apply the cement slurry at mixing ratio 1:1 and this Promote good Adhesion of the cement mortar with wall
- Normally cement mortar of mixing ratio 1:4 is used for ceiling plaster and the ratio of 1:6 is used for wall
- The mortar should be applied in slapping actions so that the mortar hold on the surface and Aluminium straight edge is taken and the mortar is leveled with the help of button marks
- A wooden float is used to finally level the surface
- The suitable finish can also be given by sponge or wooden float
- No plastering should be done on skirting area and cut in a straight fashion with the help of aluminum straight edge
- The process of external plastering is same as internal plastering
- The number of the coat of Plastering on the external area can be one or more we generally applied only 2 coat
- If we have to put two coats of plastering, we will finish the first coat first and make it rough
- After 3 days curing of first Coat final coat should be done and finish as per the requirement
- Plasterwork always start from the top of the building and goes downward
Some Important points:-
- All grooves and other features should be done when the plaster surface is wet
- Button mark tile piece should be removed and the surface should be leveled
- All the areas where dadoing will be done should be identified and rough plastering should be done, so as to facilitate good bonding for the tiles.
- The plastered surface should be cured for a minimum of 7 days
- The date of plastering should be painted on the plastered surface so that the curing period can be monitored.
- When yellow light is projected on the plastered surface from one side, the undulation can be easily seen. any rectification should be immediately when the plaster is still wet
- Check for any cracks and distortion. this could be an indicator of high silt content in sand or improper curing
- One meter marking should be made on all walls and measure the ceiling from this level.
- After plastering, the top and bottom level of all window should be checked