Overview
Let's begin with the primary purpose of plaster and its specifications.
Generally, we do plaster work for two main purposes: first, to make the surface smooth to give an appealing appearance to the structures, and second, to enhance the strength of the structure as it covers rough edges and irregular surfaces, thus promoting durability. In general practice in Nepal, the plaster thickness is either 12.5mm or 20mm with a mix ratio of 1:2, 1:4, or 1:6 cement/sand. For 20-mm-thick plaster, we perform the plaster in two steps: the first coat, the rough one, and the final coat with a smooth finish. We follow the Kathmandu district rate of 079/80 and the DUDBC code. You can get the code from our previous blog: https://www.ieccc.com.np/2024/06/cost-of-m20-grade-concrete-in-nepal.html.
Here we are about to discuss 12.5mm thick plaster with a cement/sand mix ratio of 1:4 per square meter. There are two separate rates for wall and ceiling plaster.
Calculation
We calculate these individual items to get the rate per square meter.
- Material estimate
- Material rate
- Workers rate
- Rates of tools and plants used
- Contractor overhead and profit
Quantity of mortar per square meter in 12.5 mm thick plaster work with a mix ratio of 1:4
Quantity = (12.5/1000) * 1 * 1 = 0.0125 cu.m.
For mortar, dry volume = wet volume * (1/3)
= 0.0125 * 1.33
Dry volume of mortar = 0.017
Cement Volume = (cement ratio/sum of ratios) * Dry volume of mortar
= 0.017 * (1/5)
Cement volume = 0.0034 cu.m.
Cement in kg = dry volume of cement * density of cement
= 1440 * 0.0035
Cement in kg = 5.04 kg
Bags of cement required = 5.04/50 = 0.10 bag
Sand volume = (sand ratio/sum of ratios) * dry volume of mortar
= 0.017 * (4/5)
Sand volume = 0.0136 cu.m.
Materials rate as specified on KTM district rate 079/80
Cement: 0.10 bag at 700 = Rs. 70
Sand: 0.0136 cu.m. at 3319.61 = Rs. 45.15
Total cost of material = 70 + 45.15 = Rs. 115.15
Workers, as specified in DUDBC norms
For walls
Skilled workers: 0.12 at 1185.00 = Rs. 142.20
Unskilled workers: 0.16 at 870.00 = Rs. 139.20
Total cost of workers = 142.20 + 139.20 = Rs. 281.40
For ceilings
Skilled workers: 0.12 at 1185.00 = Rs. 142.20
Unskilled workers: 0.20 at 870.00 = Rs. 174.00
Total cost of workers = 142.20 + 174.00 = Rs. 316.20
Tools and plants used
For walls
Cost of tools and plants = 3% of unskilled workers = 3% of 139.20 = Rs. 4.176
For ceilings
Cost of tools and plants = 3% of unskilled workers = 3% of 174.00 = Rs. 5.22
Total Amount
For Wall
Total amount = material rate + worker rate + tools and plant rate
= 115.15 + 281.40 + 4.176
Total amount: Rs. 400.73
For ceilings
Total amount = material rate + worker rate + tools and plant rate
= 115.15 + 316.20 + 5.22
Total amount: Rs. 436.57
Contractor overhead and profit
For walls
Contractor overhead = 15% of the total amount.
= 15% of 400.73
Contractor overhead = Rs. 60.11
For ceilings
Contractor overhead = 15% of the total amount.
= 15% of 436.57
Contractor overhead = Rs. 65.49
Total, including contractor overhead
For walls
Total cost = 400.73 + 60.11 = Rs. 460.84
For ceilings
Total cost = 436.57 + 65.49 = Rs. 502.06
Summary of the cost estimate
For walls
|
12.5mm thick cement sand plastering works with a cement sand mix ratio of 1:4. for walls |
||||||
|
Description |
Type |
Unit |
Quantity |
Rate |
Amount |
Remarks |
|
Workers |
Skilled |
MDay |
0.12 |
1185.00 |
142.20 |
|
|
Unskilled |
MDay |
0.16 |
870.00 |
139.20 |
|
|
|
Materials |
Cement |
Bags |
0.10 |
700.00 |
70.00 |
|
|
Sand |
Cu.m |
0.0136 |
3319.61 |
45.15 |
|
|
|
Tools and plants account for 3% of unskilled workers. |
4.176 |
|
||||
|
Sub-Total |
400.73 |
|
||||
|
Contractor overhead and profit at 15% |
60.11 |
|
||||
|
Total cost per cubic meter |
460.84 |
|
||||
In words: Rs. four hundred sixty and eighty-four paisa only.
For ceilings
|
12.5mm thick cement sand plastering works with a cement sand mix ratio of 1:4. for ceilings |
||||||
|
Description |
Type |
Unit |
Quantity |
Rate |
Amount |
Remarks |
|
Workers |
Skilled |
MDay |
0.12 |
1185.00 |
142.20 |
|
|
Unskilled |
MDay |
0.20 |
870.00 |
174.00 |
|
|
|
Materials |
Cement |
Bags |
0.10 |
700.00 |
70.00 |
|
|
Sand |
Cu.m |
0.0136 |
3319.61 |
45.15 |
|
|
|
Tools and plants account for 3% of unskilled workers. |
5.22 |
|
||||
|
Sub-Total |
436.57 |
|
||||
|
Contractor overhead and profit at 15% |
65.49 |
|
||||
|
Total cost per cubic meter |
502.06 |
|
||||
In words: Rs. five hundred two and six paisa only.
Others
As the heat of hydration of PPC cement is less as compared to OPC cement, the chances of appearing cracks in plaster are less, so PPC cement is recommended over OPC cement for plaster work. The calculation process for other thicknesses and mix ratios is also similar.
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