Estimating is the method of calculating or Computing of various quantities and the expected expenditure to be incurred for a particular work or project.
Costing is the process of determining the cost of the proposed work or project.
An estimate is prepared by working out the quantities and then calculating the cost at suitable rate.
Purpose of Estimating
Estimating gives an idea about the material which will be required for the construction.
Estimating helps to get an idea about the time required for the completion of project.
Estimating gives an idea about the requirement of money for the proposed work.
Estimating of the project helps to invite the tenders.
Estimating enlists the machinery required for the construction.
Estimating given an idea how many skilled and unskilled labours do the project need.
Estimating is required for the technical sanction of the project.
Purpose of Costing
To arrange the finance for the proposed work.
To know the probable cost of the project before the execution.
To know the cost of various item, well in advance, to be constructed.
It helps in financial planning to the owner before going for construction.
It makes the alternation possible when the costing of project goes beyond the capacity.
It helps in valuation of existing property.
Administrative Approval
Administrative approval is the permission given by the highest authority of the user department for execution of proposed project/work on the basis of approximate estimating of the project.
Administrative approval of any project is incurred by P.W.D. Minister, Chief Engineer, et-cetera et-cetera depending upon the nature of the project.
Technical Sanction
It is a sanction given by the highest authority of the executive department to the detailed estimate of the proposed project prepared by the executive division.
Technical Sanction means the sanction of the detailed estimate, design calculations and quantities, rates & costs of the work by competent authority of the engineering department.
Budget Provision
Budget Provision is the method which is adopted to have a proper & effective control on the expenses and production cost in an organisation.
Budget provision for a project helps in Planning & Controlling the various activities.
Types of Estimating
There're two types of estimating - Approximate Estimating & Detailed Estimating. It is also further classified as following:
1. Approximate Estimating
Plinth Area Rate Method
Cubical Content Method
Service Unit Method
Typical Bay Method
Approximiate quantities Method
2. Detailed estimating
Revised estimating
supplementary estimating
Repair and Maintenance estimating
Renoviation estimating
Revised Estimating
Revised estimating is a detailed estimate and is prepared under any one of the following condition :
When the original sanctioned estimate exceed by more than 5%.
When the expenditure of a work exceed by more than 10% of Administrative Approval.
When there's material deviations from the original proposal.
When sanctioned estimate is more than requirements.
Revised estimate is prepared and then submitted for the fresh Technical Sanction.
Supplementary Estimating
Supplementary Estimating is a detailed estimating and is prepared when additional work is required to original work due to material deviations, change in structural design or extra items.
It is necessary when further development is required during the process of work.
This supplementary amount is shown seperately in Abstract Sheet along with original amount for sanction.
For Example -If there's a bed room in which attached bathroom is not provided and then It's decided to construction an attached bathroom. In this case, Supplementary Estimating is necessary.
During the excavation work, Sometime it's necessary to revise the original estimate due to increased volume of items and at same time sanction of supplementary works.
Repair & Maintenance Estimating
It's a detailed estimating and is prepared to maintain the structure or work in proper order and in safe condition.
A building requires maintenance as Coloring, Leakage, Construction of drainage and the maintenance of lift.
For annual repairing of building 1 to 1.5% of original cost of the building is provided.
This estimate may be on the basis of time of repairs for 6 or 12 months.
Renovation Estimate
It's a type of detailed estimate and prepared for renovation of buildings, bunglows, flats and row houses.
A structure needs repairing and maintenance after some years of use.
Use of Estimates
For preliminary discussion of any project :
- Approximate Estimate.
For execution of work or Technical Sanction :
- Detailed Estimate.
If there's change in design or planning and construction cost increases by 5 to 10% :
- Revised Estimate.
During the execution of project, extra work is necessary :
- Supplementary Estimate.
To maintain or repair any structure :
- Repair & Maintenance Estimate.
Estimator - Roles and Responsibility
Estimator is the person who prepares the estimate of any civil engineering project which includes all items of the work.
An estimator is expected to be responsible for the following roles.
To prepare the list of items of project.
To calculate all the item of the work.
To prepare the estimate as per Drawing & Its specifications.
To study the rate analysis of project.
To prepare the Measurement Sheet & Abstract Sheet.
To make provision of contingencies and work charged establishment in the estimate.