Introduction

Estimating. An estimate is the process of calculating, in advance, the probable quantity of each item of work and its probable cost, from the drawings and specifications and the rates prevailing at the time. It is prepared before the work is taken up.

Why it must be prepared before construction. Because a client must know what the work will cost before he commits to it. Without an estimate there is no basis to arrange finance, obtain sanction, provide the amount in the budget, order materials, engage labour, fix the completion time, or invite tenders. It is the single document on which the whole administrative and contractual process rests.

Data required for preparing a detailed estimate

1. Drawings — complete and fully dimensioned plans, elevations, sections and detail drawings to scale. Without these no quantity can be taken out.
2. Specifications — general specifications stating the class and quality of materials, and detailed specifications stating the proportion of the mix and the method of doing each item.
3. Schedule of rates — the current district rate of materials, labour and carriage, and the rates of finished items of work.
4. Standard rate-analysis norms — the departmental norms giving the material, labour and plant required per unit of each item.
5. Standard method of measurement (IS 1200 or the departmental rules) — so that quantities are taken out and paid in a uniform way.
6. Site conditions — nature of soil, water table, availability of materials and water, lead and lift, access and transport, and local labour rates.
7. Provision for contingencies, work-charged establishment, and the cost of external services such as water supply, sanitation and electrification.

ENCE 351 §1.1 and §1.3.

(a) Estimated cost compared with actual cost

An estimate can never equal the actual cost because rates fluctuate, site conditions differ from those assumed, the design changes during execution and the tender is accepted above or below the estimated rates. A contingency of 3–5% is provided to absorb the difference.

(b) Units of measurement and payment

The unit of measurement is the unit in which the quantity is taken out; the unit of payment is the unit against which the rate is quoted. They are usually the same, but for bulk items payment is often per 100 or per 10 units (earthwork per 100 m³) to keep the rate a convenient number.

ENCE 351 §1.1 and §1.2; IS 1200.

a) Purpose of preparing a detailed estimate before construction

A detailed estimate gives the quantity and cost of every item of work separately. It is prepared beforehand in order to:

1. know the accurate probable cost and decide the financial feasibility of the work;
2. obtain technical sanction and provide the amount in the budget;
3. work out the materials, labour and plant required, and programme their supply;
4. prepare the bill of quantities and invite tenders on it;
5. fix the completion period; and
6. check the contractor's running and final bills against measured work.

b) "Estimated cost is never equal to the actual cost" — opinion

The statement is correct, and it is a property of estimating itself, not a defect of the estimator.

Why the estimated cost is never exactly the actual cost

An estimate is a forecast made before the work starts, from assumed data. The actual cost is known only after the work is finished. The two differ because:

1. Rates change. The estimate uses the rates prevailing on the day it is prepared; prices of materials, labour and fuel fluctuate during construction.
2. Time gap. Sanction, tendering and execution take months or years, during which escalation occurs.
3. Site conditions differ from those assumed — unexpected soil, rock, water table, or a longer lead than allowed for.
4. Changes in design and extra or substituted items ordered during execution.
5. Tender premium. The contract is awarded above or below the estimated rates.
6. Errors and omissions in taking out quantities, and approximations in the rate analysis.
7. Unforeseen causes — weather, strikes, accidents, scarcity of materials.

This is exactly why a contingency of 3–5% is added to every estimate, and why a revised estimate must be prepared when the cost exceeds the sanctioned amount by more than 5%. A good estimate should come within about ±5–10% of the actual cost.

In my opinion the estimate should therefore be judged not by whether it equals the actual cost — which is impossible — but by whether it falls within a reasonable margin of it. An estimate based on correct drawings, current district rates and standard norms, and honestly provided with contingencies, is a good estimate even though the final bill differs from it.

ENCE 351 §1.1.

Estimating and costing

Estimating is calculating in advance the probable quantity of each item of work and the probable cost of the whole work, from the drawings, specifications and prevailing rates.

Costing is determining the actual cost of the work after it has been executed, from measurements actually taken and money actually spent. Estimating looks forward, costing looks back; together they let the engineer forecast the cost, control it during execution, and account for it at the end.

Principle of units. Each item of work is measured in the unit that best expresses the labour and material in it — the unit follows the shape of the item.

The principle is simply this: measure in the dimensions that actually vary. If the specification already fixes a dimension, that dimension drops out of the unit. A 12 mm plaster is paid per m² because its thickness is fixed; concrete is paid per m³ because all three dimensions vary.

ENCE 351 §1.1.

a) The estimated cost is never the actual cost

Why the estimated cost is never exactly the actual cost

An estimate is a forecast made before the work starts, from assumed data. The actual cost is known only after the work is finished. The two differ because:

1. Rates change. The estimate uses the rates prevailing on the day it is prepared; prices of materials, labour and fuel fluctuate during construction.
2. Time gap. Sanction, tendering and execution take months or years, during which escalation occurs.
3. Site conditions differ from those assumed — unexpected soil, rock, water table, or a longer lead than allowed for.
4. Changes in design and extra or substituted items ordered during execution.
5. Tender premium. The contract is awarded above or below the estimated rates.
6. Errors and omissions in taking out quantities, and approximations in the rate analysis.
7. Unforeseen causes — weather, strikes, accidents, scarcity of materials.

This is exactly why a contingency of 3–5% is added to every estimate, and why a revised estimate must be prepared when the cost exceeds the sanctioned amount by more than 5%. A good estimate should come within about ±5–10% of the actual cost.

b) Data required for estimating

Data required for preparing a detailed estimate

1. Drawings — complete and fully dimensioned plans, elevations, sections and detail drawings to scale. Without these no quantity can be taken out.
2. Specifications — general specifications stating the class and quality of materials, and detailed specifications stating the proportion of the mix and the method of doing each item.
3. Schedule of rates — the current district rate of materials, labour and carriage, and the rates of finished items of work.
4. Standard rate-analysis norms — the departmental norms giving the material, labour and plant required per unit of each item.
5. Standard method of measurement (IS 1200 or the departmental rules) — so that quantities are taken out and paid in a uniform way.
6. Site conditions — nature of soil, water table, availability of materials and water, lead and lift, access and transport, and local labour rates.
7. Provision for contingencies, work-charged establishment, and the cost of external services such as water supply, sanitation and electrification.

ENCE 351 §1.1 and §1.3.

a) Principle of units of measurement

Principle of units. Each item of work is measured in the unit that best expresses the labour and material in it — the unit follows the shape of the item.

Data required for preparing a detailed estimate

Data required for preparing a detailed estimate

1. Drawings — complete and fully dimensioned plans, elevations, sections and detail drawings to scale. Without these no quantity can be taken out.
2. Specifications — general specifications stating the class and quality of materials, and detailed specifications stating the proportion of the mix and the method of doing each item.
3. Schedule of rates — the current district rate of materials, labour and carriage, and the rates of finished items of work.
4. Standard rate-analysis norms — the departmental norms giving the material, labour and plant required per unit of each item.
5. Standard method of measurement (IS 1200 or the departmental rules) — so that quantities are taken out and paid in a uniform way.
6. Site conditions — nature of soil, water table, availability of materials and water, lead and lift, access and transport, and local labour rates.
7. Provision for contingencies, work-charged establishment, and the cost of external services such as water supply, sanitation and electrification.

b) Purposes of estimating and costing

Purposes of estimating and costing

1. To know the probable cost of the work before it is built, so the owner can decide whether the work is within his means and worth doing.
2. To obtain administrative approval and technical sanction, and to provide for the amount in the budget.
3. To work out the quantities of materials required, so they can be ordered and arranged in good time.
4. To work out the labour of each category required, and to programme it.
5. To work out the plant and equipment required.
6. To fix the completion period from the quantum of work.
7. To invite tenders and prepare the bill of quantities on which contractors quote their rates.
8. To check and pass the contractor's running and final bills from actual measurements.
9. To fix the rent, valuation or compensation of a property.
10. To justify the investment from a cost–benefit point of view.

ENCE 351 §1.1–§1.3.

Estimating. Calculating in advance the probable quantity of each item of work and the probable cost of the whole work, from the drawings, the specifications and the rates prevailing at the time.

Purposes of estimating and costing

1. To know the probable cost of the work before it is built, so the owner can decide whether the work is within his means and worth doing.
2. To obtain administrative approval and technical sanction, and to provide for the amount in the budget.
3. To work out the quantities of materials required, so they can be ordered and arranged in good time.
4. To work out the labour of each category required, and to programme it.
5. To work out the plant and equipment required.
6. To fix the completion period from the quantum of work.
7. To invite tenders and prepare the bill of quantities on which contractors quote their rates.
8. To check and pass the contractor's running and final bills from actual measurements.
9. To fix the rent, valuation or compensation of a property.
10. To justify the investment from a cost–benefit point of view.

Data required for preparing a detailed estimate

1. Drawings — complete and fully dimensioned plans, elevations, sections and detail drawings to scale. Without these no quantity can be taken out.
2. Specifications — general specifications stating the class and quality of materials, and detailed specifications stating the proportion of the mix and the method of doing each item.
3. Schedule of rates — the current district rate of materials, labour and carriage, and the rates of finished items of work.
4. Standard rate-analysis norms — the departmental norms giving the material, labour and plant required per unit of each item.
5. Standard method of measurement (IS 1200 or the departmental rules) — so that quantities are taken out and paid in a uniform way.
6. Site conditions — nature of soil, water table, availability of materials and water, lead and lift, access and transport, and local labour rates.
7. Provision for contingencies, work-charged establishment, and the cost of external services such as water supply, sanitation and electrification.

ENCE 351 §1.1 and §1.3.

a) Why the estimated cost is necessary in construction work

Construction consumes large sums over a long period, and the money must be arranged and sanctioned before a single brick is laid. The estimated cost is necessary because it is the only figure available at that stage. Specifically it is needed to:

Purposes of estimating and costing

1. To know the probable cost of the work before it is built, so the owner can decide whether the work is within his means and worth doing.
2. To obtain administrative approval and technical sanction, and to provide for the amount in the budget.
3. To work out the quantities of materials required, so they can be ordered and arranged in good time.
4. To work out the labour of each category required, and to programme it.
5. To work out the plant and equipment required.
6. To fix the completion period from the quantum of work.
7. To invite tenders and prepare the bill of quantities on which contractors quote their rates.
8. To check and pass the contractor's running and final bills from actual measurements.
9. To fix the rent, valuation or compensation of a property.
10. To justify the investment from a cost–benefit point of view.

b) Data required to prepare an estimate

Data required for preparing a detailed estimate

1. Drawings — complete and fully dimensioned plans, elevations, sections and detail drawings to scale. Without these no quantity can be taken out.
2. Specifications — general specifications stating the class and quality of materials, and detailed specifications stating the proportion of the mix and the method of doing each item.
3. Schedule of rates — the current district rate of materials, labour and carriage, and the rates of finished items of work.
4. Standard rate-analysis norms — the departmental norms giving the material, labour and plant required per unit of each item.
5. Standard method of measurement (IS 1200 or the departmental rules) — so that quantities are taken out and paid in a uniform way.
6. Site conditions — nature of soil, water table, availability of materials and water, lead and lift, access and transport, and local labour rates.
7. Provision for contingencies, work-charged establishment, and the cost of external services such as water supply, sanitation and electrification.

ENCE 351 §1.1 and §1.3.

Purposes of estimating and costing

1. To know the probable cost of the work before it is built, so the owner can decide whether the work is within his means and worth doing.
2. To obtain administrative approval and technical sanction, and to provide for the amount in the budget.
3. To work out the quantities of materials required, so they can be ordered and arranged in good time.
4. To work out the labour of each category required, and to programme it.
5. To work out the plant and equipment required.
6. To fix the completion period from the quantum of work.
7. To invite tenders and prepare the bill of quantities on which contractors quote their rates.
8. To check and pass the contractor's running and final bills from actual measurements.
9. To fix the rent, valuation or compensation of a property.
10. To justify the investment from a cost–benefit point of view.

ENCE 351 §1.1.

a) Purposes of estimating

Purposes of estimating and costing

1. To know the probable cost of the work before it is built, so the owner can decide whether the work is within his means and worth doing.
2. To obtain administrative approval and technical sanction, and to provide for the amount in the budget.
3. To work out the quantities of materials required, so they can be ordered and arranged in good time.
4. To work out the labour of each category required, and to programme it.
5. To work out the plant and equipment required.
6. To fix the completion period from the quantum of work.
7. To invite tenders and prepare the bill of quantities on which contractors quote their rates.
8. To check and pass the contractor's running and final bills from actual measurements.
9. To fix the rent, valuation or compensation of a property.
10. To justify the investment from a cost–benefit point of view.

b) Units of measurement and payment

The unit of measurement is the unit in which the quantity is taken out; the unit of payment is the unit against which the rate is quoted. They are usually the same, but for bulk items payment is often per 100 or per 10 units (earthwork per 100 m³) to keep the rate a convenient number.

ENCE 351 §1.1 and §1.2; IS 1200.

a) The term "estimate"

An estimate is a written statement, prepared before the work is executed, of the probable quantity of each item of work and its probable cost, worked out from the drawings and specifications at the rates prevailing on the date of preparation.

b) Necessity of the estimated cost

It is needed to judge the financial feasibility of the work, to obtain administrative approval and technical sanction, to provide the amount in the budget, to arrange the materials, labour and plant, to fix the completion period, to invite tenders, and to check the contractor's bills.

c) Requirements for preparing a detailed estimate

Data required for preparing a detailed estimate

1. Drawings — complete and fully dimensioned plans, elevations, sections and detail drawings to scale. Without these no quantity can be taken out.
2. Specifications — general specifications stating the class and quality of materials, and detailed specifications stating the proportion of the mix and the method of doing each item.
3. Schedule of rates — the current district rate of materials, labour and carriage, and the rates of finished items of work.
4. Standard rate-analysis norms — the departmental norms giving the material, labour and plant required per unit of each item.
5. Standard method of measurement (IS 1200 or the departmental rules) — so that quantities are taken out and paid in a uniform way.
6. Site conditions — nature of soil, water table, availability of materials and water, lead and lift, access and transport, and local labour rates.
7. Provision for contingencies, work-charged establishment, and the cost of external services such as water supply, sanitation and electrification.

ENCE 351 §1.1 and §1.3.

a) Purposes of estimating and costing

Purposes of estimating and costing

1. To know the probable cost of the work before it is built, so the owner can decide whether the work is within his means and worth doing.
2. To obtain administrative approval and technical sanction, and to provide for the amount in the budget.
3. To work out the quantities of materials required, so they can be ordered and arranged in good time.
4. To work out the labour of each category required, and to programme it.
5. To work out the plant and equipment required.
6. To fix the completion period from the quantum of work.
7. To invite tenders and prepare the bill of quantities on which contractors quote their rates.
8. To check and pass the contractor's running and final bills from actual measurements.
9. To fix the rent, valuation or compensation of a property.
10. To justify the investment from a cost–benefit point of view.

Data required for estimating

Data required for preparing a detailed estimate

1. Drawings — complete and fully dimensioned plans, elevations, sections and detail drawings to scale. Without these no quantity can be taken out.
2. Specifications — general specifications stating the class and quality of materials, and detailed specifications stating the proportion of the mix and the method of doing each item.
3. Schedule of rates — the current district rate of materials, labour and carriage, and the rates of finished items of work.
4. Standard rate-analysis norms — the departmental norms giving the material, labour and plant required per unit of each item.
5. Standard method of measurement (IS 1200 or the departmental rules) — so that quantities are taken out and paid in a uniform way.
6. Site conditions — nature of soil, water table, availability of materials and water, lead and lift, access and transport, and local labour rates.
7. Provision for contingencies, work-charged establishment, and the cost of external services such as water supply, sanitation and electrification.

b) Methods of taking out quantities in building works

Four methods are in use; all four must give the same total length of wall for the same building, and that identity is the check on the work.

1. Long wall — short wall method. Walls running in one direction are taken as long walls measured centre to centre plus one breadth, and those at right angles as short walls measured centre to centre minus one breadth. Suitable when the walls of a room have different thicknesses.
2. Centre line method. The total centre-line length of all the walls is found once and multiplied by the breadth and depth of each item, deducting half the breadth for each junction. Quickest, and best when all walls have the same thickness.
3. Crossing method. The out-to-out length of the walls is taken and the overlapping corners are deducted. Suitable for simple rectangular plans.
4. Bay method. The building is divided into identical bays; one bay is worked out in full and multiplied by the number of bays, the end bays being taken separately. Suitable for long repetitive structures such as barracks and sheds.

ENCE 351 §1.1, §1.3 and Chapter 2.

Estimate. A statement prepared in advance of the probable quantity of each item of work and its probable cost, based on the drawings, specifications and current rates.

Quantity survey. The complete and itemised schedule of the quantities of every item of work in a project — the measurement side of the estimate, without the rates. When the rates are entered against those quantities it becomes the bill of quantities and hence the estimate. The person who does this work is the quantity surveyor.

Estimated cost distinguished from actual cost

ENCE 351 §1.1.

a) Purposes of estimating

Purposes of estimating and costing

1. To know the probable cost of the work before it is built, so the owner can decide whether the work is within his means and worth doing.
2. To obtain administrative approval and technical sanction, and to provide for the amount in the budget.
3. To work out the quantities of materials required, so they can be ordered and arranged in good time.
4. To work out the labour of each category required, and to programme it.
5. To work out the plant and equipment required.
6. To fix the completion period from the quantum of work.
7. To invite tenders and prepare the bill of quantities on which contractors quote their rates.
8. To check and pass the contractor's running and final bills from actual measurements.
9. To fix the rent, valuation or compensation of a property.
10. To justify the investment from a cost–benefit point of view.

"An estimate is never the actual cost of the work" — justification

Why the estimated cost is never exactly the actual cost

An estimate is a forecast made before the work starts, from assumed data. The actual cost is known only after the work is finished. The two differ because:

1. Rates change. The estimate uses the rates prevailing on the day it is prepared; prices of materials, labour and fuel fluctuate during construction.
2. Time gap. Sanction, tendering and execution take months or years, during which escalation occurs.
3. Site conditions differ from those assumed — unexpected soil, rock, water table, or a longer lead than allowed for.
4. Changes in design and extra or substituted items ordered during execution.
5. Tender premium. The contract is awarded above or below the estimated rates.
6. Errors and omissions in taking out quantities, and approximations in the rate analysis.
7. Unforeseen causes — weather, strikes, accidents, scarcity of materials.

This is exactly why a contingency of 3–5% is added to every estimate, and why a revised estimate must be prepared when the cost exceeds the sanctioned amount by more than 5%. A good estimate should come within about ±5–10% of the actual cost.

b) Types of estimate and how they differ

ENCE 351 §1.1 and Chapter 3.

a) What an estimate is, and why it must precede construction

An estimate is the advance calculation of the probable quantity of each item of work and its probable cost. It must be prepared first because the owner has to know what the work will cost before committing to it — finance must be arranged, sanction obtained, the amount provided in the budget, materials and labour organised, the completion time fixed and tenders invited. Every one of these depends on the estimate.

Requirements of estimating

Data required for preparing a detailed estimate

1. Drawings — complete and fully dimensioned plans, elevations, sections and detail drawings to scale. Without these no quantity can be taken out.
2. Specifications — general specifications stating the class and quality of materials, and detailed specifications stating the proportion of the mix and the method of doing each item.
3. Schedule of rates — the current district rate of materials, labour and carriage, and the rates of finished items of work.
4. Standard rate-analysis norms — the departmental norms giving the material, labour and plant required per unit of each item.
5. Standard method of measurement (IS 1200 or the departmental rules) — so that quantities are taken out and paid in a uniform way.
6. Site conditions — nature of soil, water table, availability of materials and water, lead and lift, access and transport, and local labour rates.
7. Provision for contingencies, work-charged establishment, and the cost of external services such as water supply, sanitation and electrification.

b) Circumstances in which each type of estimate is prepared

1. Approximate estimate — when a proposal is first mooted and only the broad size is known. Example: a 40-bed hospital costed at Rs. X per bed to obtain administrative approval.
2. Detailed estimate — once the drawings and specifications are complete and technical sanction is sought. Example: a school building measured item by item and priced by rate analysis.
3. Revised estimate — when the expenditure will exceed the sanctioned amount by more than 5%. Example: rock is met in the foundation and the excavation rate rises sharply.
4. Supplementary estimate — when additional work outside the original scope becomes necessary. Example: a compound wall and gate added to a building already under construction.
5. Complete estimate — when the full cost of bringing the work into use is wanted. Example: a residential quarter including land, water supply, sanitation, electrification, approach road and fees.
6. Annual repair and maintenance estimate — every year for an existing building. Example: whitewashing, painting and petty repairs of an office.
7. Extension / renewal estimate — when an existing work is enlarged or a worn-out part renewed. Example: re-roofing an old shed.

ENCE 351 §1.1 and Chapter 3.

The unit of measurement is the unit in which the quantity is taken out; the unit of payment is the unit against which the rate is quoted. They are usually the same, but for bulk items payment is often per 100 or per 10 units (earthwork per 100 m³) to keep the rate a convenient number.

ENCE 351 §1.2; IS 1200.

(a) Estimated cost compared with actual cost

An estimate can never equal the actual cost because rates fluctuate, site conditions differ from those assumed, the design changes during execution and the tender is accepted above or below the estimated rates. A contingency of 3–5% is provided to absorb the difference.

(b) Units of measurement and payment

The unit of measurement is the unit in which the quantity is taken out; the unit of payment is the unit against which the rate is quoted. They are usually the same, but for bulk items payment is often per 100 or per 10 units (earthwork per 100 m³) to keep the rate a convenient number.

ENCE 351 §1.1 and §1.2; IS 1200.

a) Purposes of estimating

Purposes of estimating and costing

1. To know the probable cost of the work before it is built, so the owner can decide whether the work is within his means and worth doing.
2. To obtain administrative approval and technical sanction, and to provide for the amount in the budget.
3. To work out the quantities of materials required, so they can be ordered and arranged in good time.
4. To work out the labour of each category required, and to programme it.
5. To work out the plant and equipment required.
6. To fix the completion period from the quantum of work.
7. To invite tenders and prepare the bill of quantities on which contractors quote their rates.
8. To check and pass the contractor's running and final bills from actual measurements.
9. To fix the rent, valuation or compensation of a property.
10. To justify the investment from a cost–benefit point of view.

b) Units of measurement and payment

The unit of measurement is the unit in which the quantity is taken out; the unit of payment is the unit against which the rate is quoted. They are usually the same, but for bulk items payment is often per 100 or per 10 units (earthwork per 100 m³) to keep the rate a convenient number.

ENCE 351 §1.1 and §1.2; IS 1200.

Five items measured in each of the three principal units:

The rule behind the table: an item is measured in the dimensions that vary. If the specification fixes the thickness, the item drops to an area; if it fixes two dimensions, it drops to a length.

ENCE 351 §1.2.

a) Civil works — common units of measurement and payment

b) Sanitary works — common units of measurement and payment

The unit of measurement is the unit in which the quantity is taken out; the unit of payment is the unit against which the rate is quoted. They are usually the same, but for bulk items payment is often per 100 or per 10 units (earthwork per 100 m³) to keep the rate a convenient number.

ENCE 351 §1.2; IS 1200.

a) How the items are measured, and their units

(i) Pointing work. Pointing is raking out the joints of masonry to about 15–20 mm and refilling them with a richer mortar, finished to a pattern (flush, ruled, weathered, tuck). It is measured as the area of the finished wall face, the length multiplied by the height, and not the area of the joints. Openings are deducted by the same rules as for plastering. Units: measured in m², paid per m².

(ii) Steel reinforcement. Measured as the length of each bar in position, taken from the bar bending schedule — including hooks, bends, laps and cranks — and converted to weight at the standard rate

Chairs, spacers, binding wire and rolling margin are not measured separately; they are covered by the rate. Units: measured in kg (or quintal / MT), paid per kg.

b) (i) Bill of quantities. A tabulated schedule listing every item of work in a project with its brief description, the estimated quantity, the unit, the rate and the amount. Contractors quote their rates against these quantities, so all tenders become directly comparable; the same document is later used to measure and pay for the work actually done.

(ii) Contingency. A lump sum, normally 3–5% of the estimated cost, added to the estimate to meet small unforeseen expenses and minor omissions that cannot be listed at the time of estimating. It is not meant for a change of scope — that needs a supplementary or revised estimate.

c) Why an approximate estimate is made before the detailed estimate

1. At the proposal stage the detailed drawings do not yet exist, so a detailed estimate is impossible; only an overall parameter such as plinth area or number of beds is known.
2. It is quick and cheap, whereas a detailed estimate takes considerable time and money. There is no sense in spending that effort on a scheme that may be rejected.
3. It lets the competent authority decide whether the scheme is worth pursuing and grant administrative approval, and lets the amount be provided in the budget.
4. It allows alternative schemes and sites to be compared on cost before one is chosen.
5. It fixes the order of magnitude, so that the detailed estimate prepared later can be checked against it.

ENCE 351 §1.2, §1.4 and Chapter 3.

Data required for preparing a detailed estimate

1. Drawings — complete and fully dimensioned plans, elevations, sections and detail drawings to scale. Without these no quantity can be taken out.
2. Specifications — general specifications stating the class and quality of materials, and detailed specifications stating the proportion of the mix and the method of doing each item.
3. Schedule of rates — the current district rate of materials, labour and carriage, and the rates of finished items of work.
4. Standard rate-analysis norms — the departmental norms giving the material, labour and plant required per unit of each item.
5. Standard method of measurement (IS 1200 or the departmental rules) — so that quantities are taken out and paid in a uniform way.
6. Site conditions — nature of soil, water table, availability of materials and water, lead and lift, access and transport, and local labour rates.
7. Provision for contingencies, work-charged establishment, and the cost of external services such as water supply, sanitation and electrification.

ENCE 351 §1.3.

a) (i) Lead and lift

Lead. The horizontal distance through which excavated earth or a material is carried from the point where it is dug or stacked to the point where it is used or deposited. The first 30 m is normally included in the rate for earthwork; beyond that, extra carriage is paid in stages (30 m, 100 m, 500 m, 1 km, and then per km).

Lift. The vertical height through which the material is raised or lowered above or below the ground level at the point of excavation. The first 1.5 m is included in the rate; each additional 1.5 m of lift is paid extra.

Both matter because the same item of work costs different amounts at different places. Two identical foundations, one beside the spoil dump and one 300 m away and 4 m deep, cannot carry the same rate — lead and lift are how the difference is measured and paid.

a) (ii) Rate analysis for M20 PCC in a 10 m × 10 m × 1 m raft foundation

Volume of concrete

Materials for 1 m³ of 1:1½:3 concrete

Rate analysis for 1 m³ of M20 concrete

Cost of the raft, and total materials

Reinforcement, formwork and excavation are separate items and are not included in this rate. The rates used above are illustrative — in the examination take them from the district rate and say so.

b) Method of deduction for plastering work as per IS 1200

Plastering is measured as the whole face of the wall, and openings are then deducted on a three-band rule based on the area of the opening:

Further: no deduction is made for the ends of beams, posts, rafters and steps; where the two faces of a wall are plastered in different mortars the deduction is worked out separately for each face; and the measurement is taken between the finished faces.

The rule is one of compensation. A small opening costs more labour at its reveals than the plaster it saves, so nothing is deducted; a medium one roughly balances on one face; only a large opening genuinely saves plaster, and then its reveals must be paid for separately.

c) How Nepal Government agencies take norms and rates

How Nepal Government agencies take norms and rates for rate analysis

Two different things are combined, and the distinction is the point of the question.

The procedure followed

1. The norms are taken from the relevant departmental Norms for Rate Analysis — DUDBC for building works, DoR (Standard Norms for Road Works) for roads, DWSS for water supply and sanitary works.
2. The basic rates of materials and labour are taken from the district rate published each year by the District Rate Fixation Committee for that district.
3. Carriage is added to each material for the actual lead from its quarry or market to the site, using the rate per unit per km in the district rate, supported by a lead statement.
4. Quantity from the norm × rate from the district rate = cost of that component; the components are summed.
5. Water and sundries (1–2%), overheads and contractor's profit (together about 15–20%) are added.
6. The analysed rate is entered in the abstract of cost; VAT at 13% is added at the summary stage.
7. Items not covered by any norm are analysed separately from first principles and got approved as non-scheduled items.

The reason for the split is control. Norms are technical and must not vary from district to district; prices genuinely do vary, so they are fixed locally and annually. Mixing the two up — using another district's rate, or an out-of-date norm — is the commonest audit objection.

ENCE 351 §1.4, §6.2, §6.4 and §6.5.

a) Points to be considered while measuring earthwork

1. Classification of the soil — soft/ordinary soil, hard soil, soft rock and hard rock requiring blasting are measured and paid separately, because the effort differs greatly.
2. Lead — the horizontal distance the excavated earth is carried. The first 30 m is normally included in the rate; beyond that, extra lead is paid in stages.
3. Lift — the vertical height through which the earth is lifted. The first 1.5 m is included in the rate; each additional 1.5 m is paid extra.
4. Depth of excavation, measured from the existing ground level, and taken in stages where the depth is large.
5. Dewatering — excavation below the water table or in slush is measured separately.
6. Working space and side slopes — measure the authorised dimensions of the trench as per drawing; extra excavation for the convenience of the contractor is not paid.
7. Excavation and filling kept separate, and the volume of filling measured after compaction, not loose.
8. Bulking and shrinkage — earth increases in volume when loosened and reduces when compacted, so the state in which the measurement is taken must be stated.
9. Unit — measured in m³ and generally paid per 100 m³. Surface dressing up to 30 cm deep is measured in m².

b) When a revised estimate is required

A revised estimate is a fresh detailed estimate prepared for a work already sanctioned. It becomes necessary when:

1. the expenditure exceeds, or is likely to exceed, the sanctioned amount by more than 5%;
2. the rates adopted in the original estimate have changed materially;
3. there is a substantial change in the design, specification or scope;
4. site conditions turn out to differ from those assumed; or
5. the work has been abandoned and is restarted after a long interval.

Example. A rural road was sanctioned for Rs. 2.00 crore on the assumption of ordinary soil throughout. On excavation, hard rock was met over 600 m of the alignment, raising the excavation cost and requiring additional breast walls. The anticipated cost rose to Rs. 2.35 crore — an excess of 17.5%, far beyond 5% — so a revised estimate was prepared showing the original and revised quantity and cost of each item side by side, with the reason for every variation, and was submitted for fresh sanction.

ENCE 351 §1.4 and §3.3.

a) Method of quantity estimate for road construction

A road is a long structure of nearly uniform cross-section, so it is estimated chainage by chainage rather than item by item over a plan. The procedure is:

1. Carry out a longitudinal survey and plot the ground level and the proposed formation level at every chainage (usually every 20–30 m).
2. At each chainage find the depth of cutting or height of filling, D = GL − FL for cutting, FL − GL for filling.
3. Work out the cross-sectional area at each chainage from the trapezoidal section.
4. Find the volume between successive chainages by the mid-sectional, mean-sectional or prismoidal method, keeping cutting and filling in separate columns.
5. Total the two columns separately to get the balance of earthwork, and hence the quantity to be borrowed or wasted.
6. Add the pavement layers, cross drainage, protection works and furniture as separate items, and abstract the cost.

b) Worked example

Embankment (filling) — prismoidal method

Cutting — prismoidal method

Balance of earthwork

Had the mid-sectional method been used the answers would be 5×98.28 = 491.40 and 5×126.72 = 633.60 m³ — slightly less; the mean-sectional method gives 496.80 and 642.60 m³ — slightly more. The prismoidal result lies between the two, as it always does.

ENCE 351 §5.4; formulas after Dawadi, estimating earth work.

a) Multiplying factors for a panelled door and a louvered door

Painted joinery is measured flat (the overall area of the opening, taken once) and multiplied by a factor that covers both faces and all edges:

For comparison: flush door 1.20, fully glazed 0.80, partly panelled and partly glazed 1.00.

Rules for deduction from plastering for openings in brick surfaces (IS 1200)

Plastering is measured as the whole face of the wall, and openings are then deducted on a three-band rule that depends on the area of the opening:

The logic is compensation. A small opening costs more labour at its edges than the plaster it saves, so nothing is deducted. A medium opening roughly balances on one face. Only a large opening genuinely saves plaster, and then the reveals have to be paid for separately.

Further points: no deduction is made for the ends of beams, posts and rafters; no deduction for openings up to 0.5 m² each even if there are many; and where the two faces of a wall are plastered with different mortars, the deduction is made separately for each face.

c) Bill of quantities and abstract of cost

Bill of quantities (BOQ). A tabulated schedule of every item of work in the project, giving a brief description, the estimated quantity, the unit, the rate and the amount. It is issued with the tender documents so that all contractors price the same quantities and their offers can be compared directly; it later becomes the document against which work is measured and paid.

Abstract of cost. The final summary sheet of the detailed estimate, in which the quantity of each item — brought forward from the measurement sheet — is multiplied by its analysed rate to give the amount, and the amounts are totalled. To that total are added contingencies (3–5%) and work-charged establishment (1.5–2%) to give the estimated cost of the work.

ENCE 351 §1.4 and §3.7; IS 1200.

a) Multiplying factors in painting

Multiplying factors in painting of doors and windows

Painted joinery is measured flat — the overall area of the opening, measured once — and then multiplied by a factor that accounts for the extra or lesser surface actually painted. The factor covers both faces including all edges and rebates.

Order to remember: louvered 1.80 > panelled 1.30 > flush 1.20 > partly glazed 1.00 > fully glazed 0.80. The more broken the surface, the bigger the factor; glass reduces it.

Rules for deduction from plastering for openings in brick surfaces (IS 1200)

Plastering is measured as the whole face of the wall, and openings are then deducted on a three-band rule that depends on the area of the opening:

The logic is compensation. A small opening costs more labour at its edges than the plaster it saves, so nothing is deducted. A medium opening roughly balances on one face. Only a large opening genuinely saves plaster, and then the reveals have to be paid for separately.

Further points: no deduction is made for the ends of beams, posts and rafters; no deduction for openings up to 0.5 m² each even if there are many; and where the two faces of a wall are plastered with different mortars, the deduction is made separately for each face.

c) Bill of quantities

A bill of quantities is a tabulated schedule of all the items of work in a project, each with a brief description, the estimated quantity, the unit, the rate and the amount. Its importance is that:

• all tenderers price the same quantities, so their offers are directly comparable;
• the contractor need not take out quantities himself, which saves time and avoids disputes;
• it becomes the basis for measuring and paying the work actually executed, and for valuing variations; and
• it gives the owner an item-wise picture of where the money goes.

Typical format:

ENCE 351 §1.4 and §3.7; IS 1200.

a) Quantity of a semi-circular arch

A semi-circular arch over a span L has its centre at mid-span, so the rise r = L/2 and the intrados (soffit) is a semicircle of radius L/2. If the arch ring is of thickness t measured radially and the wall is of breadth b, the arch is the volume of a half hollow cylinder.

Numerical illustration. Span L = 2.0 m, ring thickness t = 0.30 m, wall breadth b = 0.30 m:

Note the two checks that the examiner looks for: for a semi-circular arch the rise always equals half the span, and the mean-radius formula V = πR_mtb must agree with the annulus formula.

b) Quantity sheet and abstract of cost for a residential building

Measurement (quantity) sheet — quantities are taken out here:

Abstract of cost — quantities are brought forward and priced here:

Rates shown are illustrative — in the examination take them from the district rate or from your own rate analysis, and say so.

c) Bill of quantities and its importance

Bill of quantities (BOQ). A tabulated schedule of every item of work in the project, giving a brief description, the estimated quantity, the unit, the rate and the amount. It is issued with the tender documents so that all contractors price the same quantities and their offers can be compared directly; it later becomes the document against which work is measured and paid.

Abstract of cost. The final summary sheet of the detailed estimate, in which the quantity of each item — brought forward from the measurement sheet — is multiplied by its analysed rate to give the amount, and the amounts are totalled. To that total are added contingencies (3–5%) and work-charged establishment (1.5–2%) to give the estimated cost of the work.

ENCE 351 §1.4, §3.6 and §3.7.

(i) Plaster work. Plastering is measured as the area of the finished surface, length × height, taken separately for each thickness and each mix. Measurement is taken between the finished faces; no deduction is made for the ends of beams, posts and rafters. Openings are deducted on the three-band rule:

Rules for deduction from plastering for openings in brick surfaces (IS 1200)

Plastering is measured as the whole face of the wall, and openings are then deducted on a three-band rule that depends on the area of the opening:

The logic is compensation. A small opening costs more labour at its edges than the plaster it saves, so nothing is deducted. A medium opening roughly balances on one face. Only a large opening genuinely saves plaster, and then the reveals have to be paid for separately.

Further points: no deduction is made for the ends of beams, posts and rafters; no deduction for openings up to 0.5 m² each even if there are many; and where the two faces of a wall are plastered with different mortars, the deduction is made separately for each face.

Unit: measured in m², paid per m².

(ii) Cornice work. A cornice is the projecting moulded band at the junction of the wall and the ceiling or at the eaves. Because its section is fixed by the drawing and only its length varies, it is measured in running metre along the centre line of the moulding, taken separately for each pattern and each girth. Mitres and returns at corners are included in the running length; no extra is paid for them.

Unit: measured in running metre (m), paid per m. Where the cornice is very large and its section varies, it may instead be measured in m² of girth or m³ of solid volume, but this must be stated in the specification.

ENCE 351 §1.2 and §1.4; IS 1200.

a) Preliminary estimate of a government office building for administrative approval

At this stage no detailed drawings exist, so the cost is worked out from a single overall parameter using the plinth area method. The procedure is:

1. Fix the requirement — the number of officers and staff to be accommodated, and hence the floor area needed, from the departmental space standards.
2. Work out the plinth area of each floor, measured to the outer face of the walls, and total it for all floors.
3. Obtain the plinth area rate (Rs per m²) from a recently completed building of similar type, specification and locality, and update it to current rates.
4. Cost of the building = total plinth area × plinth area rate.
5. Add the external services and other charges as percentages of the building cost.
6. Prepare a brief report with a site plan, line drawings and the justification for the work, and submit it for administrative approval.

The external services and additional provisions to be specified are:

b) How the items are measured

(i) Plaster work — measured as the area of the finished surface in m², separately for each thickness and mix, with openings deducted on the three-band rule (no deduction up to 0.5 m²; one face for 0.5–3 m²; both faces plus jambs, soffits and sills above 3 m²). Paid per m².

(ii) Cornice work — measured in running metre along the centre line of the moulding, separately for each pattern and girth, mitres and returns included. Paid per m.

ENCE 351 §1.4, §3.1 and §3.6.