1. Estimating and Costing
1.1 Meaning:
- Estimating refers to the process of determining the approximate cost of a construction project or item of work based on calculations and past experience.
- Costing involves assigning specific values to these estimates based on current material prices, labor rates, and other associated costs.
1.1.2 Purpose:
- Budgeting and Planning: To ensure the project stays within financial constraints.
- Decision Making: Helps stakeholders make informed decisions about the feasibility of the project.
- Project Monitoring: To track the actual costs against the estimated costs.
1.1.3 Administrative Approval:
- This is the formal sanction given by the relevant administrative authority after the estimate has been prepared. It ensures the project can proceed with necessary funds.
1.1.4 Technical Sanction:
- This refers to the approval from a technical or engineering authority that ensures the proposed work meets required standards and specifications.
1.1.5 Budget Provision:
- The allocation of funds for a project. It is essential to ensure sufficient finances are in place to complete the work without delays.
1.2 Types of Estimates with Definition & Purpose
1.2.1 Approximate Estimate:
- Definition: A rough estimate based on limited data, often used in the initial phases of planning.
- Purpose: To provide a preliminary idea of the costs involved in a project, typically used for budgeting or feasibility studies.
1.2.2 Detailed Estimate:
- Definition: A comprehensive estimate that includes all the quantities of materials, labor, and other costs required for the completion of the project.
- Purpose: Used for precise planning, tendering, and securing financial approval.
1.3 Types and Uses of Estimates:
1.3.1 Revised Estimate:
- Definition: A new estimate prepared when there are significant changes in the scope, design, or quantities of work.
- Purpose: To update the cost estimate and reflect the changes, often required when the project deviates from the original scope.
1.3.2 Supplementary Estimate:
- Definition: An additional estimate prepared to cover unforeseen costs that arise during the execution of the project.
- Purpose: To account for additional work or changes that were not initially considered.
1.3.3 Repair and Maintenance Estimate:
- Definition: An estimate prepared for the repair and maintenance of existing structures.
- Purpose: Used for budgeting repairs or maintenance works for existing buildings or infrastructure.
1.3.4 Renovation Estimate:
- Definition: An estimate for upgrading or modifying an existing structure to improve its functionality or aesthetics.
- Purpose: To ensure that the renovation work stays within the financial resources allocated.
1.4 Roles and Responsibilities of Estimator
- Key Responsibilities:
- Prepare accurate and detailed estimates of materials, labor, and other resources.
- Ensure compliance with codes, specifications, and design standards.
- Liaise with project managers, contractors, and suppliers to gather cost data.
- Monitor project budgets and adjust estimates as needed.
- Assist in procurement processes by determining cost-effective solutions.
- Ensure timely submission of estimates to maintain project schedules.
1.5 Checklist of Items in Load-Bearing and Framed Structures
Load-Bearing Structure: Walls carry the load of the building. Key items to estimate include:
- Foundation
- Load-bearing walls
- Columns
- Roofs
- Plinth beams
Framed Structure: Uses a frame of columns and beams to support the building. Key items to estimate include:
- Foundation (spread footing or pile foundation)
- Columns
- Beams
- Slabs (RCC or Precast)
- Roof systems
1.6 Standard Formats of Measurement Sheet, Abstract Sheet, Face Sheet
- Measurement Sheet: Lists all the work items, quantities, and the rates applied to them, with unit costs.
- Abstract Sheet: A summary sheet where all the quantities of work items from the measurement sheet are consolidated to get the total cost of the project.
- Face Sheet: The first sheet in an estimate document that includes the project name, type, location, and basic details about the estimate.
1.7 Modes of Measurement and Desired Accuracy in Measurements for Different Items of Work as per IS:1200
- IS:1200 provides guidelines on how to measure quantities in building works.
- Brickwork: Measured in cubic meters, ensuring all dimensions (length, height, thickness) are accurately recorded.
- Concrete: Measured in cubic meters, ensuring precise calculations for volume.
- Steel: Measured in kilograms or tons, depending on the project.
1.8 Rules for Deduction in Different Categories of Work as per IS:1200
- General Deductions:
- For openings (windows, doors, etc.), deductions should be made from the total area or volume of the work.
- The size of openings and other voids needs to be subtracted from the total quantity.
1.9 Description/Specification of Items of Building Work as per PWD/DSR
- PWD (Public Works Department) and DSR (Delhi Schedule of Rates) provide detailed specifications for various building works.
- Example: Brickwork might require specific mortar proportions, while concrete work may specify grade and strength.
- Excavation and Foundation Work: Specific methods for digging and laying foundations.
- Concrete Work: Grade of concrete, mix ratios, curing period.
- Steel Reinforcement: Type of steel, bar sizes, and spacing.
Diagram Examples
Load-Bearing Structure:
- A simple diagram showing a wall supporting a roof or slab.
Framed Structure:
- A diagram showing columns, beams, and slabs in a typical framed structure.
Measurement Sheet:
- A table format showing items, quantities, and rates.
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