Introduction to Estimating and Costing

1. To give reasonably accurate idea of the cost through proper Estimating and Costing.

2. Estimating various types of material required.

3. Estimating categories of labour required (mason skilled, unskilled, manpower, carpenter, barbender etc.).

4. Estimating various types of equipment required (concrete mixer, excavator, vibrator etc.).

5. Estimating time of completion of project.

6. Determining the value of property.

7. To invite tender and prepare bill for payment.

8. To justify the investment from B.C ratio.

Useful to check workdone by the contractor during and after execution.

Helps in working out approximate cost of work before they are taken in hand.

It is required in inviting tenders for works & to arrange contract.

Gives an idea for the requirements of controlled material like cement, sand, brick, etc.

By fore framing a complete estimate the client can be advised on: a) Valuation of property, b) Fixation of rent, c) For fire insurance.

1. Mass, voluminous & thick work shall be taken in $m^3$ (Earthwork, Brickwork, concrete work etc.).
2. Thin & surface work shall be taken in $m^2$ (plaster, shutter, paint etc.).
3. Long & thin works shall be taken in running m (rm) (skirting, handrail, cornice).
4. Pipework or jobwork shall be taken in number (no) (wash basin, w/c, power socket etc.).

1. Drawing (working fully dimensioned)
2. Specification: a) General b) Detailed
3. Schedule of rates (List of rates)
4. Method of measurement according to IS (1200-1960) standards

1. General Excavation Rules

a) Uniform Ground: For trenches or borrow pits on uniform terrain, volume is calculated from cutting dimensions. Deadmen must be left to accurately determine average depth.

b) Non-Uniform Ground: Ground levels must be recorded before and after work. Excavation volume is computed directly from these initial and final levels.

c) Inaccessible Cutting Measurements: If direct measurement is impractical, net quantity is determined by measuring filled volume and applying deductions for shrinkage and voids.

2. Deductions and Extra Allowances for Earth Fills

a) Uncompacted Fills: A flat $10\%$ deduction is applied to gross measured volume for net quantity.

b) Compacted Fills: For fills compacted in $25\text{ cm}$ layers with watering and rolling, net cubic quantity is: $$\text{Net Volume} = \text{Measured Volume} \times \frac{\text{Dry Bulk Density of Natural Soil}}{\text{Dry Bulk Density of Compacted Fill}}$$ Testing Frequency: Density tests must be conducted every $75\text{ m}$ for channels and $200\text{ m}$ for roads.

c) Confined Consolidated Fills: No shrinkage deductions for fills in confined structural environments (e.g., under floors).

d) Loose Stacks and Transportation: A $20\%$ deduction is made from the measured gross volume when measured in loose stacks or vehicles.

e) Monsoon-Exposed Embankments: If embankments experience a monsoon season before measurement and endure normal traffic, no shrinkage deduction is applied. This must be formally recorded.

3. Measurement Precision

Length & Breadth: Nearest $0.01\text{ m}$ (for dimensions $< 25\text{ m}$), nearest $0.1\text{ m}$ (for dimensions $\ge 25\text{ m}$).
Depth: Nearest $0.01\text{ m}$.
Surface Area: Nearest $0.01\text{ m}^2$.
Volume: Nearest $0.001\text{ m}^3$.

Precision: Measured to the nearest $0.01\text{ m}^2$.

Separation: Works with different mortar mixes or binding materials are measured separately.

Element Segregation: Plastering for roofs, ceilings, and walls must be recorded distinctly.

Deductions and Additions for Openings:

i) Small ($\le 0.5\text{ m}^2$): No deduction is made. No additions for reveals, jambs, soffits, or sills.

ii) Medium ($> 0.5\text{ m}^2$ to $\le 3\text{ m}^2$): When both faces are plastered, deduct for one face only. No extra allowance for reveals/jambs. When one face is plastered and the opposite pointed, deduct from the face with the smaller reveal. If equal, apply a $50\%$ area deduction to each face.

iii) Large ($> 3\text{ m}^2$): Deductions made from both faces for full opening area. Jambs, soffits, and sills are measured and added separately.

Honeycomb Brick Plastering: Measured in square meters over gross superficial area; no deductions for openings.

Precision: Measured in cubic meters to the nearest $0.01\text{ m}^3$. Plan areas to the nearest $0.01\text{ m}^2$.

Special Conditions: Works executed underwater, in foul conditions, or liquid mud must be measured separately.

Thin Walls: Walls $\le$ one-brick thickness are measured separately in square meters.

Non-Deduction Limits: No deduction/extra payment for: i) Dissimilar member ends (joists, beams) up to $0.1\text{ m}^3$ in volume. ii) Wall openings up to $0.1\text{ m}^2$. iii) Wall/bed plates where thickness $\le 10\text{ cm}$ and bearing does not span full wall thickness. iv) Small drainage holes, iron fixtures, etc.

Fair Face Finish: Measured independently.

Flues and Chimneys: Sectional areas $\le 0.2\text{ m}^2$ are measured solid. Deduct core opening if $> 0.2\text{ m}^2$.

Honeycomb Work: Measured in square meters. Arches and Staircases: Measured separately.

Architectural Projections: Corbels, cornices, string courses, etc., measured in running meters. Chases and Grooves: Measured in running meters.

Precision: Areas to the nearest $0.01\text{ m}^2$, volumes to the nearest $0.01\text{ m}^3$.

Classification: Concrete in distinct conditions or different mix designations must be measured separately.

Non-Deduction Limits: No deductions for: Embedded steel reinforcement, embedded ends of dissimilar materials up to $500\text{ cm}^3$ in cross-section, embedded pipes/conduits up to $100\text{ cm}^3$ in cross-section, and small voids up to $40\text{ cm}^3$ in cross-section.

Columns: Measured from top of base to underside of first-floor slab.

Chajjas and Overhangs: If monolithic with a beam/lintel, common volume is included under chajja measurement. If continuing from a roof/slab, measured to the central line of bearing support.

Encased Structural Steel: Measured in cubic meters without deducting embedded steel volume.

Precision: Areas to nearest $0.01\text{ m}^2$, volumes to nearest $0.001\text{ m}^3$.

Doors and Windows: Frame/shutter joinery measured in square meters.

Shoring and Strutting: Measured in cubic meters. Bully work measured in running meters.

Mouldings: Skirtings, cornices, architraves, etc., measured in running meters.

Precision: Measured in square meters to the nearest $0.01\text{ m}^2$.

Small Openings Deduction: No deduction for openings $\le 0.5\text{ m}^2$, nor addition for their jambs/sills.

Corrugated Sheet Area Equivalents: Add the following percentages to flat projected areas: Corrugated iron sheets ($+14\%$), Asbestos cement corrugated sheets ($+20\%$), and Asbestos cement semi-corrugated sheets ($+10\%$).

Linear Elements: Pipes, poles, and similar narrow profiles measured in running meters.