UNIT 5: QUANTITY SURVEYING AND COSTING

1. Introduction to Estimation

1.1 Purpose and Importance of Estimation in Quantity Surveying

• Purpose: To determine the probable cost of a construction project before commencement.

• Importance:

  • Financial Planning: Secures funds, sanctions budgets.

  • Decision Making: Helps choose between alternative designs/methods.

  • Cost Control: Provides a baseline for comparing actual expenditures.

  • Tender & Contract: Basis for preparing tender documents and awarding contracts.

  • Valuation: Essential for property valuation, insurance, and sale/purchase.

1.2 Data Required for Preparation of Estimates

• Detailed Drawings: Plans, elevations, sections.

• Specifications: Quality of materials, workmanship, codes to follow.

• Rates: Current Schedule of Rates (CSR) or prevailing market rates for materials, labor, and equipment.

• Dimensions: Accurate measurements from drawings.

• Site Conditions: Soil type, accessibility, water table, climate.

• Legal & Administrative: Bylaws, ownership documents, permissions.

1.3 Principle of Units for Various Items of Work

[!TIP]

Common Pitfall: Using wrong units (e.g., sqm for volume) leads to major errors. Always verify the unit before calculation.

2. Types and Methods of Estimates

2.1 Rough/Preliminary Estimate

Prepared in the initial stage with limited data to get a ballpark figure.

2.1.1 Plinth Area Method

• Concept: Cost = Plinth Area × Plinth Area Rate.

• Plinth Area: Covered area at the floor level, measured externally.

• Rate: Based on cost of similar recent construction in the locality.

• Formula:

$$\text{Estimated Cost} = \text{Plinth Area (sqm)} \times \text{Rate (Rs./sqm)}$$

2.1.2 Cubic Content Method

• Concept: Cost = Cubical Content × Cubic Content Rate.

• Cubical Content: Total volume of the building (Plinth Area × Height of all floors).

• Rate: Based on cost per cubic meter of similar construction.

• Formula:

$$\text{Cubical Content (cum)} = \text{Plinth Area} \times \text{Total Height}$$

$$\text{Estimated Cost} = \text{Cubical Content} \times \text{Rate (Rs./cum)}$$

[!TIP]

Exam Focus: Be prepared to calculate a rough estimate using both methods and apply percentage additions (water supply, electrification, etc.) to the structured cost as given in past papers (Jun 2025).

2.2 Approximate Estimate

Synonymous with Rough Estimate. May use unit rate method (e.g., cost per bed in a hospital, per seat in a cinema).

2.3 Detailed Estimate

A comprehensive and accurate estimate prepared from detailed working drawings. It is the basis for tender and contract agreement.

2.3.1 Procedure for Preparation

1. Taking Off: Extract quantities from drawings (measure lengths, areas, volumes).

2. Squaring: Enter quantities in a "Take-off Sheet" or "Measurement Book".

3. Abstracting: Transfer quantities to an "Abstract Sheet" (Bill of Quantities - BOQ), grouping similar items.

4. Rate Analysis: Determine rates for each item (see Unit 6).

5. Cost Calculation: Multiply quantity by rate for each item.

6. Total Cost: Sum of all item costs + contingencies, etc.

2.3.2 Factors to be Considered During Preparation

• Accuracy of measurements.

• Correct interpretation of drawings and specifications.

• Applicability and correctness of deduction rules.

• Inclusion of all incidental items (wastage, labor for handling, etc.).

• Use of correct units and conversion factors.

• Consideration of site conditions (e.g., depth of excavation, working space).

2.3.3 Difference between Detailed Estimate and Abstract Estimate

2.4 Revised and Supplementary Estimates

2.4.1 Differences with Suitable Examples

[!TIP]

Key Difference: Revised = Change in original design. Supplementary = Extra work beyond original scope.

3. Estimation Methods for Buildings

3.1 Long Wall and Short Wall Method (Center Line Method)

• Used for load-bearing structures (brick, stone masonry).

• Long Wall: Wall running parallel to the length of the building.

• Short Wall: Wall running perpendicular to the length of the building.

• Length Calculation:

  • Long Wall Length = Center to Center length of room + ½ thickness of one long wall on each side.

  • Short Wall Length = Center to Center length of room – ½ thickness of one short wall on each side.

• Important: Lengths change for each footing (decrease for upper footings/superstructure).

• Example: For a room 5m x 4m with 230mm thick walls:

  • Long Wall (5m side) at foundation = 5 + 0.23 = 5.23m (each).

  • Short Wall (4m side) at foundation = 4 – 0.23 = 3.77m (each).

3.2 Deduction Rules in Masonry and Plastering Work

• General Rule: Do NOT deduct for openings (doors, windows, lintels) if area is less than 0.1 sqm.

• Masonry (Brickwork/Blockwork):

  • Deduct full area of openings (doors, windows, lintels, sills).

  • Exception: For segmentally arched openings, deduct only rectangular area up to the springing line; arch portion is included in masonry.

• Plastering/Painting:

  • Deduct only once for openings (area not repeated for both sides).

  • No deduction for small projections (like pilasters, corbels < 0.1 sqm).

  • For roof slab, plastering area is measured gross (no deduction for beams, openings).

[!TIP]

Mnemonic: "Masonry deducts full, Plaster deducts once, Small stuff (<0.1 sqm) no deduction."

4. Earthwork Estimation

4.1 Mid-Sectional Area Method

• Used for trenches, channels, small embankments of uniform cross-section.

• Volume = Mid-Sectional Area × Length.

• Mid-Sectional Area = Area at the mid-point of the section.

• Formula:

$$V = A_m \times L$$

where $$\displaystyle A_m $$ = area at mid-section, $L$ = length.

4.2 Mean Sectional Area Method for Roads

• Used for road embankments/cuttings with uniform cross-section over a length.

• Volume = Mean Sectional Area × Length.

• Mean Sectional Area = $$\displaystyle \frac{A_1 + A_2}{2} $$, where $$\displaystyle A_1 $$ and $$\displaystyle A_2 $$ are areas at the two ends of the length.

• Formula:

$$V = \frac{A_1 + A_2}{2} \times L$$

[!TIP]

Exam Problem: Often given chainage-wise formation levels. Calculate $$\displaystyle A_1 $$ and $$\displaystyle A_2 $$ for each interval, then sum volumes.

4.3 Volume Calculation for Embankments and Cuttings with Slopes

• Cross-section is trapezoidal (embankment) or trapezoidal with negative bottom (cutting).

• Area of Trapezoidal Section (Embankment):

$$A = (B + Zh) \times h$$

where $B$ = top width, $h$ = depth, $Z$ = side slope (horizontal:vertical, e.g., 2:1 means Z=2).

• Area for Cutting (with side slopes):

$$A = (B + Zh) \times h$$

(same formula, but $B$ is formation width, $h$ is depth of cutting).

• Volume (using Mean Area Method):

$$V = \frac{A_1 + A_2}{2} \times L$$

• Prismoidal Formula (more accurate for varying sections):

$$V = \frac{L}{6} (A_1 + 4A_m + A_2)$$

where $$\displaystyle A_m $$ = area at mid-section.

4.4 Example: Earthwork in Embankment

Given: Length $$\displaystyle L = 0.5 $$ km = 500 m, Top Width $$\displaystyle B = 4 $$ m, Depth $$\displaystyle h = 2 $$ m, Side Slope $$\displaystyle Z = 1.5:1 $$. Solution:

1. Cross-sectional area at any point (assuming uniform):

$$A = (B + Zh) \times h = (4 + 1.5 \times 2) \times 2 = (4 + 3) \times 2 = 14 \ \text{sqm}$$

2. Volume (Mean Area Method, since uniform):

$$V = A \times L = 14 \times 500 = 7000 \ \text{cum}$$

\boxed{V = 7000 \ \text{cubic meters}}

5. Detailed Estimate for Specific Construction Items

5.1 Earthwork in Excavation for Foundations

• Unit: cum.

• Measurement: Net excavated volume including working space (usually 30cm beyond outer face of footing on all sides) and up to the footing level.

• Volume Calculation: For isolated footing: $$\displaystyle V = \text{Area of footing} \times \text{Depth} \times (1 + \text{extra length for working space})^2 $$.

5.2 Lime Concrete in Foundation

• Mix: Typically 1:2:6 (Lime : Surkhi : Brick Ballast 40mm down) or as per specification.

• Thickness: Usually 100mm to 150mm over prepared sub-grade.

• Quantity: Measured in cum.

• Rate Analysis: Includes cost of lime, surkhi, brick ballast, labor (mixing, laying, compaction), and overheads.

5.3 Brickwork

5.3.1 1st Class Brickwork in Foundation and Plinth (Mix Ratio 1:4)

• Mortar: Cement : Sand = 1:4.

• Measurement: cum. Deduct volume of lintels, sills, and openings (full area × thickness of wall).

• Note: For segmental arches, deduct only rectangular portion up to springing line.

5.3.2 1st Class Brickwork in Superstructure (Mix Ratio 1:6)

• Mortar: Cement : Sand = 1:6.

• Measurement: Same as above. Thinner walls (e.g., 115mm) measured in sqm (area of wall face × thickness).

5.4 Plastering (Quantities and Cost Calculation)

• Unit: sqm.

• Thickness: Usually 12mm to 20mm.

• Measurement: Gross area of wall minus openings (deducted once). No deduction for small projections (<0.1 sqm).

• Cost Calculation: Rate per sqm includes material (cement, sand), labor (applying, finishing), and water.

5.5 Damp Proof Course (DPC)

• Purpose: Prevent dampness from ground.

• Material: Cement concrete (1:2:4) with water-proofing compound.

• Thickness: 25mm to 40mm.

• Unit: sqm.

• Measurement: Area over which DPC is laid (usually at plinth level). No deduction for openings.

5.6 Reinforced Cement Concrete (RCC)

5.6.1 Material Statement for M20 Grade Concrete

• M20 Mix: 1:1.5:3 (Cement : Fine Agg. : Coarse Agg.) by volume, water-cement ratio ~0.5.

• For 1 cum of concrete (approx. solid volume):

  | Material | Quantity | Bags (50kg) | |--------------|--------------|-----------------| | Cement | 320 kg | 6.4 | | Sand (Fine Aggregate) | 0.45 cum | - | | Coarse Aggregate (20mm) | 0.90 cum | - | | Water | 160 liters | - |

5.6.2 Quantities for Given Mix (e.g., 1:2:4 - M15)

• For 1 cum of 1:2:4 concrete:

  • Cement = 7 bags (50kg) ≈ 350 kg

  • Sand = 0.42 cum

  • Coarse Aggregate = 0.84 cum

• Procedure: For given volume $V$ of concrete, multiply each material's 1-cum quantity by $V$.

5.7 Cost Estimates for Drainage and Electrification

• Not estimated item-by-item in detailed building estimate.

• Provided as a percentage of the "Structured Cost" (cost of main structure like foundation, walls, roof).

• Typical Percentages (from past papers):

  • Water Supply & Sanitary: 5% to 8%

  • Electrification: 6% to 8%

• Cost = Structured Cost × Percentage / 100.

5.8 Culvert Construction (Different Methods and Techniques)

• Techniques: Cast-in-situ (for large/complex), Precast (for speed, quality control).

6. Rate Analysis

6.1 Definition and Factors Affecting Rate Analysis

• Definition: Process of determining the rate per unit (cum, sqm, kg) of an item of work, considering all costs involved.

• Factors Affecting Rate:

  • Material costs (brand, source, transportation).

  • Labor wages (skill, region, union rates).

  • Equipment/Plant costs (ownership, operation, maintenance).

  • Overhead charges (site office, utilities, supervision).

  • Contractor's profit margin.

  • Contingencies (unforeseen items, price fluctuation).

  • Site conditions (access, space, soil).

  • Project scale and duration.

6.2 Components of Rate Analysis

1. Material Costs: Quantity × Rate (including wastage, usually 5-10%).

2. Labor Costs: Number of laborers × daily wage × days required.

3. Equipment Costs: Hire charges or depreciation + operation cost.

4. Overhead Charges: 2-5% of (1+2+3) for site establishment, tools, etc.

5. Contractor's Profit: 10-15% of (1+2+3+4).

6. Contingencies & Fluctuation: 1-5% for unforeseen expenses and material rate changes.

6.3 Example: Rate Analysis for Lime Concrete (1:2:6)

For 1 cum of Lime Concrete (1:2:6):

• Materials:

  • Lime = 0.25 cum (≈ 8 bags of 50kg lime) @ Rs. 500/bag = Rs. 4000

  • Surkhi = 0.5 cum @ Rs. 800/cum = Rs. 400

  • Brick Ballast (40mm) = 0.9 cum @ Rs. 1200/cum = Rs. 1080

  • Total Material = Rs. 5480

• Labor: Mason, helper, labor for mixing/laying = Rs. 1500

• Overhead (2%) = 0.02 × (5480+1500) = Rs. 139.6

• Subtotal = 5480 + 1500 + 139.6 = Rs. 7119.6

• Profit (10%) = 0.10 × 7119.6 = Rs. 711.96

• Total Rate = 7119.6 + 711.96 = Rs. 7831.56/cum

\boxed{\text{Rate} \approx \text{Rs. } 7832 \text{ per cum}}

7. Cost Components and Percentages

7.1 Percentage Additions to Structured Cost

After calculating Structured Cost (cost of main building structure), add:

Note: Sequence of percentage addition may vary. Often profit is on total of materials, labor, overhead.

7.2 Key Construction Stages and Approximate Cost Percentages

8. Valuation of Buildings

8.1 Purpose of Valuation and Functions of a Valuer

• Purpose: To determine the market value or investment value of a property for:

  • Sale/Purchase, Mortgage, Insurance, Taxation, Rent fixation, Litigation.

• Functions of a Valuer:

  • Inspect property, analyze data.

  • Apply appropriate valuation method.

  • Prepare valuation report.

  • Give expert evidence if required.

8.2 Differentiation between Value, Cost, and Price

8.3 Methods of Valuation

1. Rental Method (Income Approach):

   • Value = (Net Annual Income) × Year's Purchase (Y.P.)

   • Used for let-out properties.

2. Land and Building Method (Cost Approach):

   • Value = Value of Land (by comparison) + Depreciated Cost of Building.

   • Cost of Building = Present Cost of Construction – Depreciation.

3. Development Method (Residual Method):

   • Value = (Sale Value of Developed Property) – (Cost of Development + Profit).

   • Used for undeveloped land or redevelopment.

4. Profit-Based Method:

   • Value = (Annual Profit from Business) × Year's Purchase.

   • Used for hotels, hospitals, factories.

8.4 Fixation of Standard Rent of Building

• Standard Rent = Fair Rent (based on market) limited by cost of construction and return on investment.

• Calculation (using Sinking Fund & Y.P.):

  • Step 1: Calculate Present Cost of Construction (PCC).

  • Step 2: Deduct Depreciation to get Present Value of Building.

  • Step 3: Add Value of Land.

  • Step 4: Calculate Sinking Fund (S) for the building's remaining life.

  • Step 5: Calculate Year's Purchase (Y.P.) for dual rate (interest rate i for land, sinking fund rate s for building).

  • Step 6: Annual Gross Rent = (Value of Land × i) + (Present Value of Building × (i – s)).

  • Step 7: Standard Rent = Annual Gross Rent / 12 (monthly).

9. Financial Concepts in Valuation

9.1 Sinking Fund

9.1.1 Definition and Importance

• Definition: A fund accumulated annually to replace or recover the initial investment at the end of the property's useful life.

• Importance: Ensures capital is recovered; used in standard rent fixation.

9.1.2 Determination of Sinking Fund

• Sinking Fund Coefficient (S):

$$S = \frac{i}{(1+i)^n - 1}$$

where $i$ = rate of interest (decimal), $n$ = number of years (life).

• Annual Sinking Fund = Present Value of Building × $S$.

9.2 Year's Purchase (Y.P.)

9.2.1 Concept and Calculation

• Concept: Present value of Re. 1 received annually in perpetuity or for a fixed period.

• For Perpetuity (Land): $$\displaystyle Y.P. = \frac{1}{i} $$

• For Fixed Period (Building - Dual Rate):

$$Y.P. = \frac{1}{i + s}$$

where $i$ = rate of interest, $s$ = sinking fund coefficient.

• Example (Nov 2023): Life = 15 years, $i$ = 7% = 0.07, $s$ = 4% = 0.04.

$$Y.P. = \frac{1}{0.07 + 0.04} = \frac{1}{0.11} = 9.0909$$

\boxed{Y.P. = 9.09}

9.3 Dual Rate Interest

• Concept of using two different rates:

  • Higher rate (i): For land (assumed to have perpetual life, return is interest only).

  • Lower rate (s): For building (capital is recovered via sinking fund over its life).

• Net annual return from building = i – s.

9.4 Scrap Value vs Salvage Value

9.5 Market Value vs Book Value

10. Documentation and Reports

10.1 Bill of Quantities (BOQ) and Abstract Sheet

• BOQ: A list of all items of work (from detailed estimate) with quantities, units, rates, and amounts. Tenderers quote rates against each item.

• Abstract Sheet: Summary of BOQ, grouping items into sub-headings (e.g., Earthwork, Brickwork, Finishes). Shows total cost under each sub-head.

• Format:

  | Item No. | Description | Unit | Quantity | Rate (Rs.) | Amount (Rs.) | |--------------|-----------------|----------|--------------|----------------|------------------|

10.2 Current Schedule of Rates (CSR)

• Definition: A document published by government/public agencies (e.g., PWD, CPWD) listing standard rates for various items of work based on current material and labor costs.

• Purpose: Used as a reference for preparing estimates, settling measurements, and valuing variations.

• Contains: Item description, unit, basic rate (material, labor, plant), percentage for overheads, profit.

10.3 Detailed Project Report (DPR)

10.3.1 Content and Preparation

• Purpose: Comprehensive document for project approval and financing.

• Contents:

  1. Executive Summary.

  2. Project Background & Objectives.

  3. Market Analysis & Demand.

  4. Technical Feasibility (location, design, capacity).

  5. Detailed Cost Estimates (capital cost, operating cost).

  6. Financial Analysis (IRR, NPV, payback).

  7. Implementation Schedule.

  8. Risk Analysis.

  9. Conclusions & Recommendations.

• Prepared by: Consultants, with inputs from architects, engineers, surveyors.

10.4 Tender Notice

• Definition: Public advertisement inviting tenders/bids for construction work.

• Contents: Name of work, estimated cost, time for completion, earnest money, last date, address for submission, tender documents available where.

• Issued by: Owner/Department.

10.5 Work Charge Establishment

• Definition: Site staff (engineers, supervisors, clerks) and their expenses (salaries, travel, office) directly chargeable to the project.

• Included in: Overhead charges of the estimate (typically 1-2% of project cost).

10.6 Gross Income vs Net Income

11. Special Topics

11.1 Task Work – Definition and Factors Affecting Task Work

• Definition: A fixed quantity of work (e.g., 1 cum brickwork, 10 sqm plaster) that a skilled worker should complete in a standard day.

• Factors Affecting Task Work:

  • Skill and efficiency of labor.

  • Type and quality of materials.

  • Tools and equipment used.

  • Working conditions (space, weather, supervision).

  • Method of construction.

  • Local practices and wage rates.

11.2 Fluctuation of Rates

• Definition: Variation in prices of materials, labor, and fuel during the execution period of a project.

• Treatment in Estimate: Added as a contingency (typically 2-5% of structured cost) to cover unforeseen price hikes.

• Clause in Contract: Often included as a "Fluctuation Clause" specifying how extra cost due to rate changes will be borne (by owner or contractor).