Estimation and Costing

UNIT - 01

1.Introduction to Estimation

Estimation in building construction establishes the scope, feasibility, and cost framework of a project before work begins. It ensures accurate planning for funding, tendering, and cost control by converting working drawings into quantified items and monetary values.

Types of Estimates

1. Preliminary (Rough) Estimate: Provides an early cost approximation based on basic project parameters, helping decide whether to pursue detailed planning.
2. Detailed (Itemized) Estimate: Breaks down every component—materials, labor, equipment—into precise quantities and unit rates derived from working drawings and specifications.

Roles and Responsibilities of the Estimator

1. Interpret Architectural and Engineering Drawings: Extract accurate measurements for walls, slabs, beams, and earthworks.
2. Prepare Quantity Take-offs: Use standardized methods (e.g., long-wall/short-wall, centerline) to calculate volumes and areas.
3. Perform Rate Analysis: Research market rates for materials, labor wages, and equipment costs, adjusting for location and project scale.
4. Compile and Verify Documentation: Assemble specifications, Bill of Quantities, and cost reports to support tendering and contractual agreements.

Different Items of Work

Estimators classify work into major categories to streamline measurement and costing:

1. Earthwork (excavation, backfill)
2. Masonry (brickwork, blockwork)
3. Concrete (footings, slabs, columns)
4. Carpentry and Joinery (doors, windows, formwork)
5. Finishes (plastering, tiling, painting)
6. Services (plumbing, electrical, HVAC).

Units of Measurement and Units of Payment

Each work item is measured and paid according to standard units:

Item Category	Unit of Measurement	Unit of Payment
Earthwork	Cubic meter (m³)	Per m³ excavated
Brickwork	Square meter (m²)	Per m² of wall area
Concrete	Cubic meter (m³)	Per m³ of mixed concrete
Plastering	Square meter (m²)	Per m² of finished surface
Doors & Windows	Number (No.)	Per unit installed

These units ensure clarity in cost calculations and contractual obligations.

Bill of Quantities

The Bill of Quantities (BOQ) is a structured document listing all work items, their descriptions, measured quantities, and unit rates. It serves as the financial backbone of tender documents, allowing contractors to submit comparable bids and owners to evaluate offers systematically.

2.Analysis of Rates

Rate analysis is critical for breaking down the unit cost of each work item into its constituent parts—materials, labor, equipment, overheads, and profit. This ensures that the estimator can assign realistic, market‐based rates to every line in the Bill of Quantities.

Purpose and Importance

Each rate serves as the building block for the detailed estimate.

1. It translates quantities from the drawings into monetary terms.
2. It helps in comparing bids from different contractors on an “apples-to-apples” basis.
3. It provides transparency in cost control throughout the project lifecycle.

Procedure for Rate Analysis

1. Gather Market Data

   1. Obtain current prices for materials (e.g., cement, sand, bricks) from suppliers.
   2. Survey local labor wages and equipment rental rates.

2. Quantify Inputs

   1. Refer to the Bill of Quantities to extract required material volumes and labor hours.
   2. Classify each element by its unit of measurement (m³, m², number).

3. Compute Unit Rates

   1. Materials: (Unit price × consumption per unit of work)
   2. Labor: (Number of workers × daily wage × productivity factor)
   3. Equipment: (Hourly or daily rental rate × usage hours)
   4. Add allowances for overheads (10–15%) and profit margin (5–10%).

4. Validate and Update

   1. Cross-check against historic data and published standard rates.
   2. Adjust for site conditions, location, and project scale.

Rates of Common Construction Materials

1. Cement: Rs. ____ per bag
2. Sand: Rs. ____ per cubic meter
3. Aggregate: Rs. ____ per cubic meter
4. Bricks: Rs. ____ per thousand
5. Reinforcement Steel: Rs. ____ per tonne

These benchmark rates must be updated regularly to reflect market fluctuations.

Categories of Labor and Their Skills

1. Unskilled Workers Perform basic site duties: earthwork, material handling.
2. Semi-Skilled Workers Assist skilled trades (e.g., mixing mortar, shuttering).
3. Skilled Workers Execute specialized tasks: masonry, carpentry, plumbing, electrical.
4. Supervisory Staff Oversee crews, ensure quality, coordinate between trades.

Number of Laborers and Daily Wages

Work Item	Labor Category	No. of Workers	Daily Wage (Rs)
Brickwork	Skilled masons	4 masons + 2 helpers	500 / 150
Plastering	Plasterers & helpers	3 plasterers + 2 helpers	450 / 150
Concreting	Concrete workers	5 workers + 2 helpers	400 / 150

3.Transportation and Logistics in Rate Analysis

Accurate estimation requires breaking down every cost component involved in moving materials from source to site. This section covers how vehicle capacities, hiring charges, and ancillary fees feed into the unit rate for each work item.

Load-Carrying Capacity of Vehicles

Estimators classify transport into categories based on payload and volume, choosing the most economical option for each material:

• Small Trucks/Vans: 1–3 t payload; suited for small, frequent deliveries
• Medium Tippers: 5–10 t payload; ideal for sand, aggregates, soil
• Heavy-Duty Tippers: >10 t payload; used for bulk cement, steel, large stones

Selecting the right vehicle minimizes idle runs and overall haulage cost.

Transportation Hiring Charges

Hiring charges combine the vehicle’s daily rental rate with running costs:

1. Daily Hire Rate (e.g., Rs 3,000/day for a 10 t tipper)
2. Distance Cost = Lead (km) × Rate per km (e.g., Rs 20/km)
3. Loading/Unloading Allowance (hourly/day basis)

Total Trip Cost = Daily Hire + Distance Cost + Handling Allowance

GST, Lead, Lift, and Overhead Charges

• GST: 5 % on transport and hiring services; e.g., on a Rs 3,800 haulage cost, GST = Rs 190
• Lead: Horizontal haul distance; directly proportional to fuel and wear-and-tear cost
• Lift: Vertical height for hoisting materials; charged per m³-m (e.g., Rs 2/m³-m)
• Overheads: Site supervision, equipment maintenance, temporary facilities (10–15 % of direct cost)

These elements ensure full recovery of all site logistics expenses.

Water Charges

When on-site water isn’t free, estimators include:

• Procurement Cost (Rs per kL)
• Pumping and Distribution Fees

Example: If water costs Rs 30/kL and a project uses 100 kL, total = Rs 3,000.

Contractor’s Profit

A standard profit margin (5–10 %) is added over the fully loaded cost (materials + labor + transport + overheads) to ensure business viability.

Factors Affecting Rate Analysis

Several dynamic factors can alter transport and logistics costs:

• Market Fluctuations: Fuel and material price volatility
• Seasonal Constraints: Monsoon delays increase idle time and demurrage
• Site Accessibility: Narrow roads or height restrictions may require smaller vehicles or extra handling
• Scale of Operation: Bulk hires often reduce per-unit vehicle charges
• Local Regulations: Tolls, night-haul restrictions, and permits can add unforeseen costs

Estimators must adjust rates continuously to reflect real-time conditions.

UNIT - 02