Overview
Let's first have a brief idea of stone masonry.
Stone masonry is a structure constructed using stone and mortar. This technique has been used since ancient times for the construction of temples, houses, walls, retaining structures, etc. . The stone used may be dressed or undressed. The dressed structure is called ashlar masonry, and the undressed stone structure is rubble masonry. Here we are about to deal with rubble masonry work. This structure is basically used for a strong foundation. This structure is used to protect the landslides and scoring by the river on the river banks.
For the calculation of the rate per cubic meter, we are using the basic norms.
- Kathmandu District Rate
- DUBDC Norms
We have discussed details on these norms in our previous blog: https://www.ieccc.com.np/2024/06/cost-of-m20-grade-concrete-in-Nepal.html?m=1.
Calculations
Quantity estimate
Unlike brick masonry, as we have dealt with in our previous blog, https://www.ieccc.com.np/2024/06/cost-of-brickwork-per-cubic-meter.html?m=1,
Where we have calculated the number of bricks using the formula total volume by standard volume of bricks, we cannot find the number of stones as we are dealing with irregular-shaped stones. So what we do in general practice is take a volume, as the stone doesn't come in a regular shape, we need to chisel the stone to avoid vertical joints in the structure and distribute a load to a larger area. To compensate for this, we add an extra 25% to the provided volume.
For 1 cubic meter of random ruble masonry work with a mix ratio of 1:6 (cement/sand),
Volume of stone used = 1 + 25% extra
Volume of stone used = 1.25 cu.m.
For cement sand mortar calculation, we don't know what actual volume of stone has been taken in the structure, so in general practice, we take the mortar as having taken 40% of the total volume.
Volume of mortar = 40% of masonry volume
Volume of mortar = 0.4 cu.m.
Considering 5% wastage, the stone shape is irregular, and you need more mortar to fill up the voids.
Wastage Volume = 5% of 0.4
Waste volume = 0.02 cu.m.
So the total volume of mortar = 0.4 + 0.02 = 0.42 cu.m.
Now the remaining process is just as similar as we have done for brickwork and M20-grade concrete.
Dry volume of mortar = 1.33 * wet volume (for mortar we take 33% and for concrete we take 54%)
= 1.33 * 0.42
Dry Volume of Mortar = 0.56
Volume of cement
Cement Volume = Dry Volume of Mortar * (cement ratio)/(sum of ratios)
= 0.56 * (1) / (1 + 6)
Cement volume = 0.08 cu.m.
Cement in kg = cement volume * cement density
= 0.08 * 1440
Cement in kg = 115.2 kg
Number of bags of cement = cement in kg/wt per bag of cement
= 115.2 / 50
Number of bags of cement = 2.3 bags
Volume of sand
Sand volume = dry volume of mortar * (sand ratio)/(sum of ratios)
= 0.56 * (6) / (1 + 6)
Sand volume = 0.48 cu.m.
Volume of water = 70 ltr (from DUDBC code)
Cost of construction material as per Kathmandu district rate: 079/80
Quarry stone: 1.25 cu.m. at 2366.08 = Rs. 2957.60
Cement: 2.3 bags at Rs. 700 = Rs. 1610.00
Sand: 0.48 at Rs. 3319.61 = Rs. 1593.41
Water: 70 ltr at 0.2 = Rs. 14
Construction materials cost = 2957.60 + 1610 + 1593.41 + 14 = Rs. 6175.01
Workers rate analysis as per norms of DUDBC and KTM district rate 079/80
Skilled workers = 1.5 at 1185.00 = Rs. 1777.50
Unskilled workers = 5 at 870.00 = Rs. 4350
Workers rate per m3 = 1777.50 + 4350 = Rs. 6127.50
Cost of tools and plants used
Hire of equipment = 3% of unskilled workers = 3% of 4350 = Rs. 130.5
Total Cost = Construction Material Cost + Workers Cost + Tools and Plant's Cost
= 6175.01 + 6127.50 + 130.5
Total Cost = Rs. 12433.01
Including contractor 15% overhead and profit
Overhead = 15% of total cost
= 15% of 12433.01
Overhead = Rs. 1864.95
Total with overhead cost = 12433.01 + 1864.95 = Rs. 14297.96
Summarizing the cost estimate
|
Rubble masonry works include the supply of hard stone blocks, the preparation of cement mortar, and the construction of walls up to 5 meters high (haulage distance up to 10 meters). cement mortar 1:6 |
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Description |
Type |
Unit |
Quantity |
Rate |
Amount |
Remarks |
|
Workers |
Skilled |
MDay |
1.50 |
1185.00 |
1777.50 |
|
|
Unskilled |
MDay |
5.00 |
870.00 |
4350.00 |
|
|
|
Materials |
Quarry stone |
Cu.m |
1.25 |
2366.08 |
2957.60 |
|
|
Cement |
Bags |
2.30 |
700.00 |
1610.00 |
|
|
|
Sand |
Cu.m |
0.48 |
3319.61 |
1593.41 |
|
|
|
Water |
Ltr. |
70.00 |
0.20 |
14.00 |
|
|
|
Tools and plants account for 3% of unskilled workers. |
130.50 |
|
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|
Sub-Total |
12433.01 |
|
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|
Contractor overhead and profit at 15% |
1864.95 |
|
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|
Total cost per cubic meter |
14297.96 |
|
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The cost per cubic meter of random rubble stone masonry work is Rs. fourteen thousand two hundred ninety-seven and ninety-six paisa only.
Others
The cost of materials and workers in different districts of Nepal may vary, so you need to consider the corresponding district rate to calculate the rate analysis for the other districts.
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