Estimation and Costing
Estimate is required to be prepared for every work to know quantity of material and cost of work.
In civil engineering, word estimate is related with various civil engineering structures like buildings, roads, dam, canal, railways, bridge etc.
MEANING OF THE TERMS - ESTIMATING AND COSTING
(A) Estimating :
- An estimate can be defined as 'the procedure or method of working out the probable cost of a work'. An estimate is prepared by working out the quantities and then calculating the cost at suitable rates.
- Before the construction work of any structure is started, calculation of quantities of various items of work and its probable cost is done. This is known as estimating. Before starting any civil engineering work or project, it is necessary to know its approximate cost by calculating quantity of various items and multiplying it by unit rates of materials.
- As far as estimating is concerned, it is done by studying and analysis of drawing and specification. Estimate of a work is governed by quantity and quality aspect. Quantity is related with drawings and quality is related with specifications of materials and workmanship.
- Measurement sheets.
- Abstract sheets.
(B) Costing :
- Costing is defined as 'the determination of actual cost of the work before the execution of it'.
- To know the cost of work, detail estimate is prepared in measurement sheets and the probable cost of various items is entered in the abstract sheets.
- To arrange the finances for the work to be executed, costing is necessary.
PURPOSE OF ESTIMATING AND COSTING
- Before taking up any project for execution the owner should know the total cost of the work, so that financial arrangements can be made well in advance.F
- From estimate, the quantities of various materials required may be worked and necessary arrangements for the same can be made. The estimate also gives rough idea of the time required for completion of work.
- The number and kind of workers of different categories required to complete the work in the specified time can be found out. An estimate is immensely useful in planning and execution of any work.
(A) Purpose of Estimating :
1. To know the approximate cost of work.
2. For technical sanction of the project.
3. To know the approximate quantity of various materials and labours required.
4. To give an idea for keeping control over expenditure during construction.
5. For inviting tenders and to arrange contract.
6. To have an idea about the time of completion of project.
(B) Purpose of Costing :
1. To determine probable cost of work before execution and to study feasibility of project.
2. Costing of various items required for construction of structures is known well in advance and accordingly arrangement of finance can be made.
3. It helps in financial planning to owner before going for construction.
4. Addition and alterations in planning and designing can be done if the costing goes beyond the capacity.
Types of Estimate
Different types of estimate are given below :
1.Preliminary estimate or Approximate or Abstract or Rough cost estimate.
i. Plinth area estimate.
ii. Cube rate estimate or Cubical content estimate.
iii. Approximate quantity method estimate.
iv. Service Unit Method
v. Typical Bay Method
2.Detailed estimate or item rate estimate.
3.Revised estimate.
4.Supplementary estimate.
5.Revised & Supplementary and estimate.
6.Annual repair and Annual maintenance estimate
