Quantity Surveying & Costing (Lab) (CE-505) - Unit 2 Short Notes

UNIT 2: FUNDAMENTALS OF MEASUREMENT & COSTING OF BUILDING ELEMENTS

I. Fundamentals of Measurement & Units (Theoretical & IS Code Basis)

A. Principles of Measurement

• Definition: The process of determining the quantities of various items of work from drawings and specifications for cost estimation and billing.

• Core Purpose: To provide a common, unambiguous basis for pricing and payment.

• General Rules (IS 1200 series):

  • Measurement "in the flesh": Quantities are measured from the actual finished work dimensions, not from the nominal sizes of materials (e.g., measure wall length from center-to-center of walls, deducting for openings).

  • Order of Measurement: Length → Width/Height → Depth/Thickness.

  • Grouping: Similar items of work are grouped together.

• Gross vs. Net Measurement:

  • Gross Measurement: Measurement before any deductions (e.g., total wall area).

  • Net Measurement: Measurement after making all permissible deductions (e.g., net plaster area after deducting door/window areas). This is the standard for billing.

[!TIP] Exam Focus: Always state whether a quantity is "gross" or "net." The default in BOQ is net measurement after all specified deductions.

B. Standard Units of Measurement

• Reference: Primary reference is IS 1200 (Parts 1 to 25) – "Method of Measurement of Building and Civil Engineering Works." Each part covers a specific trade (e.g., IS 1200 (Part 3) for Brickwork).

• Key Conversion: 1 cum = 1000 litres; 1 tonne = 1000 kg = 10 quintals.

C. Importance of Accurate Measurement

• Financial Impact: Directly controls project cost, interim payments, and final account settlement.

• Contractual Basis: Forms the Bill of Quantities (BOQ), a contractual document.

• Sources of Error:

  • Misreading scales on drawings.

  • Incorrect application of deduction rules.

  • Omitting items or double-counting.

  • Unit conversion mistakes.

• Precision: Manual take-off should be to the nearest 0.01 m (1 cm) for linear dimensions, leading to 0.0001 sqm or 0.000001 cum precision.

II. Measurement of Building Elements (Core Practical Lab Focus)

A. Earthwork & Site Preparation

• Items Measured: Excavation (topsoil, trenches, pits), filling/embankment, earth removal.

• Key Formula - Prismoidal Formula (for irregular volumes):

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

Where:

*   $L$ = Length/interval between cross-sections

*   $$\displaystyle A_1, A_2 $$ = Areas of first and last cross-sections

*   $$\displaystyle A_m $$ = Area of mid-section

• Simplified Average End Area Method (for regular sections):

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

• Lab Tip: Always measure excavation in excess of the structure's footprint (allowance for working space, slope).

B. Concrete Work

• In-situ Concrete: Measured in cum for each distinct element (isolated footing, combined footing, column, beam, slab, staircase).

• Deductions:

  • Volume of reinforcement (if specified in IS 1200).

  • Volume of embedded items > 0.1 sqm in cross-section (e.g., pipes, ducts).

  • Openings > 0.1 sqm are not deducted from concrete volume (they are deducted from formwork).

• Pre-cast Concrete: Measured in nr or cum as specified. Includes fabrication, transport, and erection.

• Lab Exercise: For a slab, calculate net concrete volume = Gross volume - (Volume of all beams/columns below slab).

C. Masonry Work

• Units: cum for brick/block/stone masonry.

• Measurement: Length × Height × Thickness. Measured net after deductions.

• Deductions for Openings (IS 1200 (Part 3)):

  • Doors, Windows, Ventilators: Area deducted once only from the wall in which they are set.

  • Lintels & Sills: Not measured separately if included in masonry item. Their volume is included in the masonry deduction.

  • Chases & Recesses: Deducted if exceeding 0.02 cum in volume.

• Lab Tip: For a wall with a door, Net Masonry Area = (Gross wall area) - (Area of door opening).

D. Finishing Works

• Plastering/Painting: Measured in sqm.

  • Deductions: For openings > 0.5 sqm, deduct once only. For openings ≤ 0.5 sqm, no deduction.

  • Additions: For reveals, jambs, soffits of openings > 0.5 sqm, add 50% of the opening area.

• Flooring: Measured in sqm.

  • Deduct area of permanent fixtures (columns, pedestals) > 0.1 sqm.

  • Skirting/ dado measured in running metres (rm) or sqm as specified.

• Ceiling Finishes: Measured in sqm of finished ceiling area (gross, no deductions for fixtures).

E. Joinery & Fittings

• Doors/Windows/Frames: Measured in nr.

  • Specification must include size (e.g., 1.0m x 2.1m), type (panel, casement), material (wood, UPVC, aluminum), and finish.

  • Fittings (Hinges, Handles, Locks): Usually measured in nr and grouped with the respective door/window item or in a separate schedule.

• Lab Exercise: Create a door schedule listing: Item No., Size, Type, Material, Finish, No. of Fittings.

F. Other Elements

• Roofing: Sheeting (sqm), Trusses (nr or kg), Tiles (sqm or nr).

• Steel Reinforcement: Measured in quintals (q) or tonnes (t). Requires a Bar Bending Schedule (BBS) detailing bar size, length, number, and total weight.

  • Weight Calculation: $$\displaystyle Weight (kg) = \frac{d^2}{162} \times L $$ (where $d$ = dia in mm, $L$ = length in m).

• Plumbing & Electrical: Primarily measured in nr (for fittings) and in rm (for pipes, conduits). Complex systems may have separate MEP BOQs.

III. Methods of Estimating & Costing (Applied in Lab Context)

A. Types of Estimates

B. Cost Analysis & Rate Analysis

• Components of Unit Rate (for 1 cum of concrete 1:4:8):

  1. Material Cost: Cement, sand, aggregate (including wastage ~5%).

  2. Labor Cost: Mason, helper, mixer operator (based on productivity).

  3. Plant & Equipment Cost: Mixer, vibrator (depreciation, fuel).

  4. Overheads & Profit: Site overheads (10-15%), contractor's profit (10%).

• Formula (Approximate):

$$\text{Unit Rate} = \frac{\text{Total Direct Cost (Mat+Lab+Plant)}}{1} \times (1 + \text{Overhead}\%) \times (1 + \text{Profit}\%)$$

• Sources: Standard Schedule of Rates (SOR) from CPWD/PWD, Standard Data Books.

C. Application of Cost Indices

• Concept: To adjust a past estimate to present-day prices.

• Simple Formula:

$$\text{Present Cost} = \text{Past Cost} \times \frac{\text{Present Index}}{\text{Past Index}}$$

• Common Indices: CPWD/NSIC cost indices, wholesale price index (WPI) for construction materials.

IV. Preparation of Bills of Quantities (BOQ) & Documentation

A. Structure and Format of BOQ

• Grouping: Items grouped by Trades/Sections (e.g., 1.0 Earthwork, 2.0 Concrete, 3.0 Brickwork).

• Preamble: Notes explaining abbreviations, measurement rules, and inclusions/exclusions.

B. Abbreviations and Terminology

• c/s = centre to centre

• g/s = gross

• n/s = net

• excl. = excluding

• incl. = including

• @ = at the rate of

• a/c = as per contract

• Prov. = provision for

• U.C. = under cover

C. Totals, Summaries, and Grand Summary

1. Trade Summary: Sum of "Amount" column for each trade section.

2. Grand Summary: Sum of all Trade Summaries. This is the Total Project Cost (excluding contingencies, etc.).

3. Presentation: Use neat tables, double lines for totals, clear headings.

V. Introduction to Digital Tools in QS Lab

A. Basic Take-off Software (e.g., Bluebeam, CostX)

• Core Function: Digitally measure lengths, areas, volumes, and counts from PDF/DWG drawings.

• Workflow:

  1. Calibrate drawing scale.

  2. Use measurement tools (polygon for area, linear for length, count for items).

  3. Organize measurements into "Sets" or "Tabs" (e.g., "Slab Concrete," "Wall Plaster").

  4. Export measurements (usually to CSV/Excel).

B. Spreadsheet Application (MS Excel) for BOQ

• Template Setup:

  • Columns: A: Item No., B: Description, C: Unit, D: Quantity, E: Rate, F: Amount.

  • Formula in F2: =D2*E2 (drag down).

  • Total Row: Use SUM(F:F) for grand total.

• Formatting: Currency format, borders, freeze panes, clear headings.

C. Integration: Digital Workflow

[Digital Drawing (PDF/DWG)]

        ↓ (Take-off in Bluebeam/CostX)

[Measurement Set (CSV Export)]

        ↓ (Copy-Paste/Link to Excel)

[BOQ Excel Template]

        ↓ (Link to Rate Analysis Sheet)

[Dynamic BOQ - Auto-updates if quantities change]

[!TIP] Common Pitfall: Always verify a sample of digital measurements against manual take-off to ensure scale calibration and tool usage are correct.

VI. Laboratory Exercises & Report Writing

A. Step-by-Step Lab Procedure

1. Drawing Comprehension: Study all relevant drawings (plan, section, elevation, detail).

2. Systematic Take-off:

   • Element-by-Element: (e.g., measure all foundations first, then all columns).

   • Floor-by-Floor: For multi-storey buildings.

   • Use tally sheets or pre-formatted Excel sheets to record raw measurements.

3. Compilation: Transfer raw measurements to a computation sheet showing calculations (e.g., Wall Length = (Plan Length) - (Door Width)).

4. Verification & Checking:

   • Check 1: Sum of all net areas/volumes should be less than gross.

   • Check 2: Cross-check with approximate methods (e.g., total concrete volume ≈ plinth area × average height × factor).

   • Check 3: Ensure all openings are accounted for in deductions.

B. Preparation of Lab Report/Assignment

• Standard Format:

  • Title Page: Subject, Experiment/Topic, Roll No., Date.

  • Objective: What was measured and why.

  • Methodology: Brief description of IS code followed, tools used (manual/digital).

  • Calculations: Show key computations clearly. Include sample computation sheets.

  • Final BOQ: Neat, tabulated, with trade summaries and grand summary.

  • Conclusion: Summary of total quantities and any observations/difficulties.

• Submission: Often requires annotated drawings (with dimensions highlighted) and tally/computation sheets as annexure.

[!TIP] Exam/Submission Checklist:

\boxed{\text{✓ All units consistent?}} \quad

\boxed{\text{✓ All deductions applied per IS 1200?}} \quad

\boxed{\text{✓ BOQ totals match computation sheets?}} \quad

\boxed{\text{✓ Report neat, signed, and referenced?}}