Estimation is a process of calculating quantities and costs of various items required in connection with a work.
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Types of Estimation
There are five Types Of Estimation
a. Approximate Estimate
b. Detailed Estimate
c. Quantity Estimate
d. Revised Estimate
e. Supplementary Estimate
a) Approximate Estimate :- This is also known as preliminary/rough estimate. This estimate is prepared to work-out an approximate cost of the project in a short period without going into details. This estimate is done for preliminary financial evaluation of different alternatives and for administrative sanctions.
b) Detailed Estimate :- This estimate is prepared by working out the quantities of different items of work and then working out the cost by multiplying the quantities by their respective rates. In detailed estimate provisions for any other expenses like contingencies, T&P, work-charged establishment etc. are added to the above cost to calculate the total amount required for project completion.
c) Quantity Estimate :- Quantity Estimate/Quantity Survey is a part of detailed estimate which list the quantities of all the items required to complete the project. These quantities are worked out from the drawings. The purpose of Quantity Estimation is to quantities are worked out from the drawings. The purpose of Quantity Estimation is to prepare bill of quantities.
d) Revised Estimate :- It is a detailed estimate for the revised quantities or revised rates of items of work originally provided in the estimate without any deviation in original design and specifications approved for the project. It is required when the material cost or the material quantities deviates significantly (> 5%) from sanctioned value.
e) Supplementary Estimate :- This estimate is worked out during progress of work due to any changes or addition of works to originally approved. A supplementary estimate is different from the revised estimate in the aspect that, the former is worked out for the works which are not present in the original design whereas the latter is worked out when there is a deviation of materials from original proposal.
Abstract Estimate:- This is the third and final stage in a detailed estimate. The quantities and rates of each item of work, arrived in the first two stages, are now entered in an abstract form. The total cost of each item of work is now calculated by multiplying the quantities and respective rates.
Terminology
Taking off in quantity surveying: This is the process of finding out the quantities for various items of works involved in a project by taking off various dimensions from the plan, sections of the drawings and tabulating in a measurement seat. The measurement sheet contains following columns
like description, number, length, breadth, thickness/height and quantity.
Contingencies: There are certain expenses which are incidental in nature and it is not possible to predict them with reasonable accuracy. To cater all such expenses an additional amount of 3% to 5% of estimated cost is provided in the total estimate.
Lump sum items: These are small items, such as, front architectural or decoration work of a building, fireplace, site-cleaning and dressing, etc., for which detailed quantities cannot be taken out easily or it takes sufficient time to find the details. For such items a lump-sum rate is provided in the estimate.
Work charged establishment: During the construction of a project considerable number of skilled supervisors, work assistance, watch men etc., are employed on temporary basis. The salaries of these
persons are drawn from the L.S. amount allotted towards the work charged establishment.That is, establishment which is charged directly to work. An L.S. amount of 1½ to 2% of the estimated cost is provided towards the work charged establishment.
Tools and plants (T&P): Use of special type of tools and plants, like concrete mixture, batching plants or WMM plant, etc., may be required for efficient execution of large projects. To cater such expenses about 1% to 1.5% of the estimated cost is allotted under the head tools and plants (T&P).
Day work: During execution of a project there may be certain type of works, for which the actual
quantities of labor required is difficult to measure. For example fine architectural works,and drawings in the wall. The payments towards such items are made on the basis of actual number of days or actual quantity of materials required. Such works are known as day works.
Sub work: A large project may consist of several independent small works. Such small works are known as sub work. For example setting of a university may contain the construction of administrative building, classrooms, faculty chambers, hostels and faculty residences.Estimations for each of the sub works are done separately and accounts of expenditure are kept sub work wise.
Deposit work: The construction or repair works whose cost is not met through government funds but
through some non-government sources is called deposited work. The cost is deposited in cash or placed at disposal of the divisional officer. The works executed for municipalities or other bodies fall under this category.
Provisional quantities: During preparation of an estimate if it is apprehended that additional quantities against some items may be required due to variation of site conditions, then those quantities are estimated separately from the dimensions of the drawing and kept separately in the
estimate under a heading Provisional Quantities.
Provisional sum: While preparing the estimate some amount is provided in it for items whose details
regarding cost or specifications are unknown during the preparation. For example the cost and specifications for a lift may be unknown during estimation for the building. Such amounts are known as provisional sum. However the payments for these provisional items are done as per actual rate.
Prime Cost: Prime cost is the purchase cost of articles at a shop. Prime cost is generally referred to the supply of a particular article and not for carrying out a work. The prime cost includes the cost for carriage but excludes the cost of fixing or fitting. For example: the door and window fittings are purchased from the shop at a cost of Rs 1000.00. The transportation cost is Rs.50.00 and the cost for fixing and fitting is Rs.100.00. Then the prime costs of the fittings are Rs. 1050.00.
Actual Cost: The actual cost is the actual expenditure incurred in completing a work excluding profit
but including other incidental, establishment and travelling charges. The actual cost is the cost incurred by the contractor to complete the project.
Capital Cost: Capital cost is the actual amount incurred in completing a work. This includes
expenditure incurred in surveying, designing, planning, drawing, cost of material, equipment, laborers, supervision, legal expenses, travel expenses, taxes, electricity and water charges, contingencies and any other expenses related to the work but excluding profit.
Work value: This is the total amount provided for all scheduled items of work in the estimate. Thus
work value is the estimated value for the work excluding the amount for contingencies,work charged establishment, tools and plants etc. as per actual rate.
Bill of quantities (BOQ):
This is defined as a list of brief descriptions and estimated quantities. This lists in a tabular form all the items of work involved in connection with estimate for a project with the description, corresponding quantity, unit rate and amounts column. The columns indicating unit rate and amounts are kept blank. BOQ is provided in a tender form for item rate tenders. Contractors’ put up their own competitive rates and calculate the totals to offer their estimate amount to complete the whole work. The BOQ is also required to calculate the quantities of different materials required for the project.
like description, number, length, breadth, thickness/height and quantity.
Contingencies: There are certain expenses which are incidental in nature and it is not possible to predict them with reasonable accuracy. To cater all such expenses an additional amount of 3% to 5% of estimated cost is provided in the total estimate.
Lump sum items: These are small items, such as, front architectural or decoration work of a building, fireplace, site-cleaning and dressing, etc., for which detailed quantities cannot be taken out easily or it takes sufficient time to find the details. For such items a lump-sum rate is provided in the estimate.
Work charged establishment: During the construction of a project considerable number of skilled supervisors, work assistance, watch men etc., are employed on temporary basis. The salaries of these
persons are drawn from the L.S. amount allotted towards the work charged establishment.That is, establishment which is charged directly to work. An L.S. amount of 1½ to 2% of the estimated cost is provided towards the work charged establishment.
Tools and plants (T&P): Use of special type of tools and plants, like concrete mixture, batching plants or WMM plant, etc., may be required for efficient execution of large projects. To cater such expenses about 1% to 1.5% of the estimated cost is allotted under the head tools and plants (T&P).
Day work: During execution of a project there may be certain type of works, for which the actual
quantities of labor required is difficult to measure. For example fine architectural works,and drawings in the wall. The payments towards such items are made on the basis of actual number of days or actual quantity of materials required. Such works are known as day works.
Sub work: A large project may consist of several independent small works. Such small works are known as sub work. For example setting of a university may contain the construction of administrative building, classrooms, faculty chambers, hostels and faculty residences.Estimations for each of the sub works are done separately and accounts of expenditure are kept sub work wise.
Deposit work: The construction or repair works whose cost is not met through government funds but
through some non-government sources is called deposited work. The cost is deposited in cash or placed at disposal of the divisional officer. The works executed for municipalities or other bodies fall under this category.
Provisional quantities: During preparation of an estimate if it is apprehended that additional quantities against some items may be required due to variation of site conditions, then those quantities are estimated separately from the dimensions of the drawing and kept separately in the
estimate under a heading Provisional Quantities.
Provisional sum: While preparing the estimate some amount is provided in it for items whose details
regarding cost or specifications are unknown during the preparation. For example the cost and specifications for a lift may be unknown during estimation for the building. Such amounts are known as provisional sum. However the payments for these provisional items are done as per actual rate.
Prime Cost: Prime cost is the purchase cost of articles at a shop. Prime cost is generally referred to the supply of a particular article and not for carrying out a work. The prime cost includes the cost for carriage but excludes the cost of fixing or fitting. For example: the door and window fittings are purchased from the shop at a cost of Rs 1000.00. The transportation cost is Rs.50.00 and the cost for fixing and fitting is Rs.100.00. Then the prime costs of the fittings are Rs. 1050.00.
Actual Cost: The actual cost is the actual expenditure incurred in completing a work excluding profit
but including other incidental, establishment and travelling charges. The actual cost is the cost incurred by the contractor to complete the project.
Capital Cost: Capital cost is the actual amount incurred in completing a work. This includes
expenditure incurred in surveying, designing, planning, drawing, cost of material, equipment, laborers, supervision, legal expenses, travel expenses, taxes, electricity and water charges, contingencies and any other expenses related to the work but excluding profit.
Work value: This is the total amount provided for all scheduled items of work in the estimate. Thus
work value is the estimated value for the work excluding the amount for contingencies,work charged establishment, tools and plants etc. as per actual rate.
Bill of quantities (BOQ):
This is defined as a list of brief descriptions and estimated quantities. This lists in a tabular form all the items of work involved in connection with estimate for a project with the description, corresponding quantity, unit rate and amounts column. The columns indicating unit rate and amounts are kept blank. BOQ is provided in a tender form for item rate tenders. Contractors’ put up their own competitive rates and calculate the totals to offer their estimate amount to complete the whole work. The BOQ is also required to calculate the quantities of different materials required for the project.
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