Following requirement are necessary for preparing an estimate in civil engineering.
+ Detail information about workmen/staff compensation
+ BSR – Basic schedule rates
Units of MeasurementsThe units of measurements are mainly sub-divided for their nature, shape and size for making payments to parties/contractors. The following principle unit of measurements generally consists;
- Running meter – It is taken into account when width specified – handrail, cornice, fencing, handrail,
- Numbers – Single units like doors, windows, truss if specified are expressed in numbers
- Square meter / Square feet – surface measurement, plastering, painting, partition wall ( when thickness specified)
- Cubic meter / Cubic feet – Earth work, concrete, masonry etc specified in cubic meters.
Techniques of Estimating and costing in civil engineering
- Long and short wall technique
- Center line technique
- Combination of both techniques
Long and short wall technique
In this particular method the length of room is assumed to be long and perpendicular to long wall considered to be short wall. In this method, first mark the center line of both the walls and long wall calculation to be done first taking full length into account. For short wall each half breadth of long wall shall be deducted from both ends.
Also Read : Basic Engineering of Hume pipe
Center line technique
It is suitable where cross section area is similar. Total center line length is multiplied by breadth and depth to determine the quantity. This method helps us to estimate quick and accurate calculations.
Combination of both techniques
It is combination of the both above mentioned techniques. It is adopted when outer wall and the inner walls are having different thickness. In that case, a center line technique is applied to outer walls and long –short wall techniques for internal walls.
This is one of the practical methods as most of the estimation and costing in civil engineering can be done using this technique.
How to prepare an estimate
Preliminary estimate is required for budgetary approval from higher authorities and many other aspects. Now days, estimation are also made to understand the Investment return of the project. The estimate is prepared from the practical knowledge and cost of the similar project works in nearby area. However up to 10% additional quantity should be taken in to account for contingencies. Following are the methods used for preparation of estimates,
- Plinth area
- Cubical content
- Unit base
The cost of construction is calculated by multiplying plinth area with plinth area rate. Generally plinth area rate are considered in respect of quality, labour & materials, height of building, type of roofs and number of storey.
Cubical contents method
Cubical contents method is used for high rise buildings. It is rather accurate and practical method to determine building cost. The cost of structure is calculated approximately as the volume of buildings multiplied by cubic rate (local).
Unit Base method
In this method the cost of building is calculated by multiplying the total number of units with unit rate of each separate item. In case of hotel ‘guest room’ is considered to be as one unit and dividing by total expenditure incurred of similar building in the nearby area.
But you cannot get accurate rate due to fluctuation in material price with respect to current rate. Therefore better to compare material rate of latest completed projects.
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