Procedure or Method of Estimating in Construction | Civil Engineering

In the construction industry, estimation is a fundamental process used to projection the probable cost of a project before actual construction begins. Budgeting, Project planning, resource allocation are all made easier with an accurate estimate. It helps both the client and the contractor understand the financial scope of the project, compare tenders and avoid spending beyond budget. To prepare an accurate estimate, a organized approach or procedure must be followed. In this article, we are able to give an explanation for the manner or approach of estimating in construction, the kinds of estimates, the significance of estimation and the step-by means of-step method utilized by expert estimators.

What Is Construction Estimating?

Construction estimating is a process of predicting the total cost that will be required to complete a construction project. This involves determining the quantities of materials, labor, equipment, and overheads, applying their respective unit rates to find the overall cost of the project.

The principal purpose of estimation is to confirm the financial viability of the project and to adequately plan the resources well in advance of commencing the work.

Importance of Estimating in Construction

Estimation plays an important role in the success of any construction project. Below are some key reasons why estimation is important:

1. Budget Preparation: Assists clients and contractors in making proper financial resource planning.

2. Project Feasibility: Decides whether the project is viable economically before commencement.

3. Tendering and Bidding: Offers cost basis for presenting competitive bids at tenders.

4. Resource Planning: Guarantees that materials, equipment, and manpower are available when needed.

5. Cost Control: It serves as a benchmark to check expenditure during the construction process.

6. Client Confidence: Builds trust between stakeholders through transparency in cost forecasting.

7. Avoiding Disputes: Reduces the likelihood of cost-related disputes during project execution.

Types of Estimates in Construction:

Depending on the stage of the project or the level of detail required, estimates can be carried out in several ways. The major types include:

1. Preliminary Estimate

Also called an approximate estimate, it is prepared during the initial stage of project planning. It gives an approximate idea regarding the cost that will be involved, thereby helping in deciding the feasibility of the project.

2. Estimate in Detail

This is a comprehensive estimate prepared after the detailed drawings and specifications are available. It includes item-wise quantities and rates with the total cost and is utilized for tendering and budgeting.

3. Quantity Estimate

It includes taking off the quantities of all items of work from drawings and specifications. It is the basis for rate analysis and cost computation.

4. Revised Estimate

Prepared when there are large changes in project scope, design, or rates so that the original estimate is no longer accurate.

5. Supplementary Estimate

Additional estimate prepared for extra works or additions not included in the original design.

6. Abstract Estimate

A summarized form of the detailed estimate showing the cost under major heads such as earthwork, concrete, steel, etc.

7. Definitive Estimate

An accurate estimate prepared after all the designs, drawings, and specifications have been finalized for financial sanction.

 Step by step method of Estimating:

1. Data Collection for the Project : The first step in estimation is collecting all necessary project information, which includes:

Drawings: The following drawings like Architectural drawing, structural drawings, Electrical drawings, Plumbing drawings and HVAC drawings are the major inputs for prepare the accurate estimate and costing.

Specifications: Detailed specification and descriptions of materials, workmanship, tools and tackles & standards to be followed.

Site Conditions: Types of soil, location, accessibility and environmental factors. Client Requirements: If any Special requirements, design modification or project-specific conditions. Without complete and accurate project data, the estimate may be inaccurate and misleading the project.

2. Selection of the Estimation Method: There are different methods of estimation depending on the nature, size, and stage of the project:

(a) Detailed Estimate In details :

• Estimate utilized when complete specifications and drawings are available.
• Multiplies the quantities of each piece of work by unit rates.
• Most accurate and commonly used method.

(b) Plinth Area Estimate Based on the plinth area (built-up area) of the building. divides the area by a common rate per square meter. Used in the initial stage for feasibility studies.
(c) Cube Rate Estimate uses the cubic content of the building (length, width, and height). Suitable for multi-story buildings.
(d) Approximate Quantity Estimate :Quantity Calculates total wall length and multiplies by standard rates. Faster but less accurate.
(e) Revised or Supplementary Estimate used when additional tasks are added or the scope of work changes. The method selected depends on the purpose of the estimate and the availability of project data.

3. Quantity Takeoff :

The estimation process's most crucial step is this. It involves: Measuring all work items as per the drawings (e.g., excavation, concrete, brickwork). In accordance with standard formats like CPWD or PWD, listing each item separately under relevant headings. utilizing appropriate formulas and unit measurements to calculate the total quantities. For example: Earthwork = Length × Breadth × Depth Brickwork = Length × Height × Thickness All measurements should be accurate and follow the latest construction measurement standards.

4. Determination of Rates :

• Each item of work is then assigned a unit rate based on:
• Material Cost: Including transportation, wastage, and taxes.
• Cost of Labor: Wages determined by productivity and labor rates in the area. Equipment/Machinery Cost: If any tools or machines are required.
• Overheads: Administrative, safety, site management, and other indirect costs.
• Profit Margin: For the contractor's profit, typically 10% to 15% is added.
• You can get rates from:
• Schedule of Rates (SOR)
• Market prices
• Previous project data Quotation from vendors or subcontractors

5. Preparation of Abstract Estimate :

After calculating the cost of each item, an abstract estimate is prepared.

• This includes:
• Serial number of each item
• Description of work
• Quantity
• Unit Rate
• Total cost of each item
• Finally, all individual costs are added to determine the total estimated cost of the project.

6. Adding Contingencies and Miscellaneous :
The Costs to cover unexpected expenses and minor changes in project execution , a percentage (usually 3–5%) is added to the total cost as contingencies. Moreover, additional costs may include Preliminary charges for Work establishment, Consultancy fees, Inspection charges , Escalation allowances. These are all ensure that the estimate remains realistic and practical even if small changes occur during construction.

7. Finalizing and Submitting the Estimate:
The completed estimate should be reviewed thoroughly to check for: Omissions or duplications Errors in mathematics Correct application of rates and formulas Once finalized, the estimate is submitted for: the client, consultants, or authorities' approval Use in tendering, budget allocation, and project planning

Tips for Accurate Estimation

 1. Always use updated drawings and specifications. 

2. Visit the site before starting estimation. 

3. Use reliable sources for unit rates. 

4. Keep historical data from past projects. 

5. Double-check all calculations. 

6. Include realistic contingencies.

 7. Use estimating software for precision.

 

Conclusion
The process of estimation is structured and requires accuracy, attention to detail and technical expertise, not just a estimate at the cost. When a project is properly estimated, delays and disputes are avoided and the financial success of the project's is assured. Regardless of whether the project is a simple building or a complex infrastructure one, efficient construction planning, decision-making, and cost control require a reliable estimate.