Requirement for plastering
Cement and sand requirement for plastering of brick wall depends on mostly two factors:
- Thickness of Plaster
- Mix Ratio (Cement:Sand)
Thickness of cement plaster:
- recommended thickness of cement plaster is 6 mm (for ceiling and concrete plastering), 12 mm (for internal wall plastering and plane surface of brickwork) & 15 mm or 20 mm (for external wall plastering and rough surface of brickwork) are used in building construction.
- 6 mm thick cement plaster are used for ceiling and concrete plastering
- 12 mm thick cement plaster are used for internal wall plastering and plane surface of brick wall
- 15 mm or 20 mm theek cement plaster used for external wall plastering and rough surface of brick wall
Mix ratio for cement plaster:
- there are several types of mix ratio used for brick wall plastering, ratio of cement and sand for plastering depends on types of work and plastering types it is rough or plane surface.
- recommended mix ratio of cement and sand for plastering of plane and rough surface of brick wall, concrete wall and ceiling are 1:3, 1:4, 1:5 & 1:6 are used.
- 1:3 mix ratio of cement and sand are used for plastering of external wall prone to sever climatic condition and for repairing work
- 1:4 mix ratio of cement and sand are used for external brick wall plastering and ceiling plastering
- 1:5 mix ratio of cement and sand are used for internal brick wall plastering when fine sand is not available
- 1:6 mix ratio of cement and sand are used for internal wall plastering when fine sand is available.
Number of bags of cement required per square metre for plastering
1 plastering thickness of 12mm & cement sand ratio of 1:4
For a Sample calculation, I will assume a 12mm (0.012m) thick plaster and a mix ratio of 1:4 for plastering of 1 square metre brick wall
● Step-1: we know given area of brick wall = 1 sq m
● Step-2: Volume of brick wall plaster = Area X Thickness = 1 X 0.012 = 0.012 m3
Since wet volume is always less than the dry volume. For converting wet volume to dry volume of mortar we will multiply 1.33 into wet volume.
The dry volume of mortar required for brick wall plastering = 1.33 X Dry volume of plaster = 1.33 X 0.012 = 0.01596 m3.
● Step-3: The mix ratio of mortar is 1:4, So total ratio = 1+4 = 5 in which one part is cement and 4 part is sand
Cement required = ⅕ X 0.01596 = 0.003192 cu m ( cubic meter)
Sand required = ⅘ X 0.01596 = 0.01277 cu m
● Step-4: To get the weights of materials required in multiply it with its density and convert cubic feet into cubic meter
Cement required = 0.003192 cum X 1440 kg/cum = 4.6 Kgs
Since Sand density is 1620 kg/m3
Then quantity of sand = 0.01277 ×1620 = 21Kgs.
● Ans :- 21 Kgs (0.01277 cu m) sand and 0.092 bags (4.6 Kgs) cement required per square metre for plastering in 12mm thick plaster & ratio 1:4.
2 plastering thickness of 20mm & mix ratio of 1:4
For a Sample calculation, I will assume a 20mm (0.020) thick plaster and a mix ratio of 1:4 for plastering of 1 sq m brick wall
● Step-1: we know given area of brick wall = 1 sq m
● Step-2: Volume of brick wall plaster = Area X Thickness = 1 X 0.020 = 0.020 cu m
Since wet volume is always less than the dry volume. For converting wet volume to dry volume of mortar we will multiply 1.33 into wet volume.
The dry volume of mortar required for brick wall plastering = 1.33 X Dry volume of plaster = 1.33 X 0.020 = 0.0266 cu m.
● Step-3: The mix ratio of mortar is 1:4, So total ratio = 1+4 = 5 in which one part is cement and 4 part is sand
Cement required = ⅕ X 0.0266 = 0.00532 cu m ( cubic meter)
Sand required = ⅘ X 0.0266 = 0.02128 cu m
● Step-4: To get the weights of materials required in multiply it with its density and convert cubic feet into cubic meter
Cement required = 0.00532 cum X 1440 kg/cum = 7.7 Kgs
Since Sand density = 1620 kg/m3
Then quantity of sand = 0.02128 × 1620 = 34.5 Kgs.
● Ans :- 34.5 Kgs (0.02128 m3) sand and 0.154 bags (7.7 Kgs) cement required per square metre for plastering in 20mm thick plaster 1:4.
How many bags of cement and quantity of sand will plaster one square metre of a brick wall?
