Plastering is done to protect the wall or ceiling and also to remove surface imperfections caused by brickwork and to make the wall smooth for painting. Plastering is done by using different materials like Cement, Clay, Lime etc., In this post we are discussing about cement plastering work.
Calculation of Cement and Sand required or plastering:
We have to remember some general points before going to plastering calculation, they are
- Cement mortar ratio for wall plastering is 1:6, and for ceiling is 1:4. The ratios mentioned are volumetric ratios of cement and sand. (i.e., Cement:Sand = 1:6, 1 part of cement is mixed with 6 parts of sand for plastering).
- Plastering thickness should not be more than 12-20 mm including two coats.
- In two coat plastering work, the first coat of plastering is done with thickness 12 - 15 mm and this coat is called as "Primary Coating" (or) "Rough Coating".
- Second coating is done with 8 mm thickness, and this is called as "Secondary Coating" (or) "Finish Coat".
Steps involved in calculation of plastering quantities:
1. Calculate the wall area to be plastered in sqm (m2). Take assumption as 100 m2.
2. Consider the ratio and thickness of plastering. (i.e., ratio 1:6 & thickness 12 mm).
3. Now we know the area of plastering and thickness, so by using this calculate the Total Volume of Plastering.
4. We know the Total Volume of Plastering and Ratio of plastering so we can calculate the Volume of Cement & Sand required individually.
Step 1 : Assumptions
Area of plastering = 100 m2,
Ratio of plastering = 1:6,
Thickness of plastering = 12 mm.
Step 2 : Volume of plastering
Volume of Plastering = Area of plastering X Thickness
= 100 m2 X 0.012 m = 1.2 m3
(Take 20% extra quantity, to fill joints & Wastage)
Step 3 : Find individual quantities of cement and sand required
Plastering Ratio = 1:6
Total parts = 1+6 = 7
Quantity of cement required = 1.2 X 1/7 = 0.17 m3
Density of cement is 1440 kg/m3
Weight of cement = 1440 X 0.17 = 245 kg.
Quantity of Sand required = 1.2 X 6/7 = 1.03 m3
Density of sand is 1920 kg/m3 (It depends on moisture content)
Weight of sand = 1920 X 1.03 = 1978 kg.
Step 4 : Quantity of water required
Quantity of water required is 20% of Total dry material (Cement & sand)
Quantity of water = 20% (weight of cement + weight of sand)
= 20% (245+1978) = 445 kg = 445 ltr
Like that we can calculate the requirement of cement, sand and water for any ratio and thickness of plastering work.
