Estimating & Costing - Complete Notes PDF

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All Theory Topics Covered as per GGSIPU Syllabus for Estimating & Costing-1...

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UNIT-1 Introduction to Quantity Surveying/Estimating and its Importance: Definition: An estimate is a calculation of the quantities of various items of work, and the expenses likely to be incurred there on. The total of these probable expenses to be incurred on the work is known as estimated cost of the work. The estimated cost of a work is a close approximation of its actual cost. Importance: To give a reasonably accurate idea of the cost. An estimate is necessary to give the owner a reasonably accurate idea of the cost to help him decide whether the work can be undertaken as proposed or needs to be curtailed or abandoned, depending upon the availability of funds and prospective direct and indirect benefits. For government works proper sanction has to be obtained for allocating the required amount. Works are often let out on a lump sum basis, in which case the Estimator must be in a position to know exactly how much expenditure he is going to incur on them. Purpose: An estimate is necessary to give the owner a reasonably accurate idea of the cost to help him decide whether the works can be undertaken as proposed or needs to be curtailed or abandoned, depending upon the availability of funds and prospective direct and indirect benefits. For government works proper sanction has to be obtained for allocating the required amount. Works are often let on a lump sum basis, in which case the Estimator must be in a position to know exactly how much expenditure he is going to incur on them 1. Estimating Materials: From the estimate of a work it is possible to determine what materials and in what quantities will be required for the works so that the arrangements to procure them can be made. 2. Estimating Labor: The number and kind of workers of different categories who will have to be employed to complete the work in the specified time can be found from the estimate 3. Estimating Plant: An estimate will help in determining amount and kind of equipment needed to complete the work. 4. Estimating Time: The estimate of a work and the past experience enable one to estimate quite closely the length of time required to complete an item of work or the work as a whole, whereas the importance of knowing the probable cost needs no emphasis, estimating materials, labor, plant and time is immensely useful in planning and execution of any work.

Types of Estimates: PRELIMINARY ESTIMATE: This is an inexact estimate to find out a rough cost in a short time which enables the authority concerned to consider the financial aspect of the scheme, for according sanction to the same. Such an estimate is framed after knowing the rate of similar works and from practical knowledge in various ways for various types of works such as: a. Plinth area or square-meter method: The floor area of the proposed structure is worked out, and then multiplied by a suitable rate. This rate of construction per square meter of floor area is worked out by dividing the known cost of construction of a similar building by the floor area of that building. b. Cubic rate or cubic meter method: This method is more accurate than the square meter of floor area method. because the depth of foundations and the height of the structure above the ground level are the additional dimensions taken into consideration. The American Institute of Architects recommends considering the actual cubic space enclosed within the outer surfaces of the outside walls and contained between the outer surfaces of the roof and 15 cm below the finished surface of the lowest floor. c. Service unit or unit rate method: Buildings are constructed to serve a specific purpose. For example hospitals are designed to accommodate certain number of beds. Each bed is then considered a service unit. Hotels are designed to accommodate certain number of guest rooms. Each guest room is considered a service unit. Same applies to offices, residential houses, etc. Whenever a building is constructed the Engineer or the architect keeps the record of the place, actual cost, number of service units, and the year of construction. From this record, it is possible to work out the cost per service unit. This cost is then adjusted to account for inflation, and peculiarities of the project under consideration. Then the adjusted cost per service unit is simply multiplied by the number of service units in the proposed project to get an approximate cost estimate. 2. DETAILED ESTIMATE: This consists of detailed particulars of the quantities, rates, and costs of all the materials required for satisfactory completion of a project. Quantities of all materials of work are calculated according to their respective dimensions on the drawings on a measurement sheet. Multiplying these quantities by their respective rates in a separate sheet, the cost of all items of work are figured out individually and then summarized, i.e abstracted (which is the detailed actual estimated cost of work). All other expenses required for satisfactory completion of the project are added to the above cost to frame the total of a detailed estimate. A detailed estimate is accompanied by:a. Report b. Specifications c. Detailed drawings showing plans, different sections, etc.

1.

d. e.

Design data & calculation The basis of rates adopted in the estimate

Steps in Preparation of an Estimate: There are three clearly defined steps in the preparation of an estimate. 1 . Taking out quantities : In the first step of taking out quantities, the measurements are taken off from the drawings and entered on measurement sheet or dimension paper. The measurements to be taken out would depend upon the unit of measurement. For example, in the case of stone masonry in superstructure, length, thickness and height of the walls above plinth level would be taken out from the drawings and entered on the measurement sheet, whereas, in the case of plastering only the lengths and heights of the walls would be entered. Obviously, the unit of measurement in the first case is cubic meter and that in the second case is square meter. 2. Squaring out : The second step consists of working out volumes, areas, etc. and casting up their total in recognized units. 3. Abstracting : In the third step all the items along with the net results obtained in the second step are transferred from measurement sheets to specially ruled sheets having rate column ready for pricing. The second and third steps above are known as working up. All calculations in these stages and every entry transferred should be checked by another person to ensure that no mathematical or copying error occurs.

Details of Measurement & Quantities: The complete work is divided into various items of work such as earth work concreting, brick work, R.C.C. Plastering etc., The details of measurements are taken from drawings and entered in respective columns of prescribed preformed. The quantities are calculated by multiplying the values that are in numbers column to Depth column

Abstract of Cost: The cost of each item of work is worked out from the quantities that already computed in the details measurement form at workable rate. But the total cost is worked out in the prescribed form is known as abstract of estimated form. 4%of estimated Cost is allowed for Petty Supervision, contingencies and Unforeseen items.

UNIT-2 General Principle of Units of Measurements:   

Single units work like doors, windows, trusses etc., are expressed in numbers. Works consists linear measurements involve length like cornice, fencing, hand rail, bands of specified width etc., are expressed in running metres (RM) Works consist areal surface measurements involve area like plastering, white washing, partitions of specified thickness etc., and are expressed in square metres (m2) Works consists cubical contents which involve volume like earth work, cement concrete, Masonry etc are expressed in Cubic metres Table below shows units of measurement of various items of civil engineering works based on IS 1200. Units of measurement

Units of payment

1. Earthwork in excavation

CUM

Per CUM

2. Earthwork in filling in foundation trenches

CUM

Per CUM

3. Earth work in filling in plinth

CUM

Per CUM

1. Lime concrete in foundation

CUM

Per CUM

2. Cement concrete in lintels

CUM

Per CUM

3. RCC in slab

CUM

Per CUM

4. Cement concrete or RCC in chujja, sunshade

CUM

Per CUM

5. Lean concrete in roof terracing (thickness specified)

SQM

Per SQM

6. Cement concrete bed

CUM

Per CUM

7. Reinforced concrete sunshade (specified width and height)

CUM

Per CUM

3

Damp proof course (DPC) – thickness mentioned

SQM

Per SQM

4

Brick work 1. Brickwork in foundation

CUM

Per CUM

2. Brickwork in plinth

CUM

Per CUM

3. Brickwork in super structure

CUM

Per CUM

4. Thin partition walls

SQM

Per SQM

5. Brickwork in arches

CUM

Per SQM

Sl. No.

Particulars of item

1

Earthwork

2

Concrete

6. Reinforced brickwork 5

CUM

Per CUM

CUM

Per CUM

1. Doors and windows frames or chaukhats, rafters, beams

CUM

Per CUM

2. Shutters of doors and windows (thickness specified)

SQM

Per SQM

3. Doors and windows fittings (like hinges, tower bolts, sliding bolts, handles)

Each

Per Each

1. Steel reinforcement bars etc. in RCC and reinforced brick work

Quintal

Per Quintal

2. Bending, binding of steel reinforcement

Quintal

Per quintal

3. Rivets, bolts and nuts, anchor bolts, lewis bolts, holding down bolts

Quintal

Per quintal

4. Iron hold fasts

–

–

5. Iron railing (height and types specified)

–

–

6. Iron grills

SQM

Per SQM

1. RCC and RB slab roof (excluding steel)

CUM

Per CUM

2. Lean concrete roof over and inclusive of tiles or brick or stone slab etc. (thickness specified)

SQM

Per SQM

3. Centering and shuttering formwork

SQM

Per SQM

4. AC sheet roofing

SQM

Per SQM

1. Plastering – cement or lime mortar (thickness and proportion specified)

SQM

Per SQM

2. Pointing

SQM

Per SQM

3. White washing, color washing, cement washing, (number of coats specified)

SQM

Per SQM

4. Distempering (number of coats specified)

SQM

Per SQM

Stone work 1. Stone masonry

6

7

8

9

Wood work

Steel work

Roofing

Plastering, points and finishing

5. Painting, varnishing (number of coats specified)

SQM

Per SQM

1. 25mm cement concrete over 75mm lime concrete floor (including lean concrete)

SQM

Per SQM

2. 25mm or 40mm cement concrete floor

SQM

Per SQM

3. Doors and window sills (CC or cement mortar plain)

SQM

Per SQM

11

Rain water pipe / plain pipe

RM

Per RM

12

Steel wooden truss

Each

Per each

13

Glass panels (supply)

SQM

Per SQM

14

Fixing of glass panels or cleaning

Each

Per Each

10

Flooring

NOTE: SQM = Square Metre CUM = Cubic Metre RM = Running Metre

Methods for Measurement of civil engineering works:

o o o

o o o

The rules for measurement of each item are invariably described in IS – 1200. However some of the general rules are listed below: 1. Measurement shall be made for finished item of work and description of each item shall include materials, transport, labor, fabrication tools and plant and all types of overheads for finished the work in required shape, size and specification. 2. In booking, the order shall be in sequence of length, breadth and height or thickness. 3. All works shall be measured subject to the following tolerances. Linear measurement shall be measured to the nearest 0.01m. Areas shall be measured to the nearest 0.01 SQM Cubic contents shall be worked out to the nearest 0.01 cum. 4. Same type of work under different conditions and nature shall be measured separately under separate items. 5. The bill of quantities shall fully describe the materials, proportions, workmanships and accurately represent the work to be executed. 6. In case of masonry (stone or brick) or structural concrete, the categories shall be measured separately and the heights shall be described as: From foundation to plinth level From plinth to first floor level From first floor to second floor level and so on.

Different Methods of Taking Out Quantities:-

The quantities like earth work, foundation concrete, brickwork in plinthand super structure etc., can be workout by any of following two methods: a) Long wall - short wall method b)Centre line method. c) Partly centre line and short wall method. 1.LONG WALL-SHORT WALL METHOD In this method, the wall along the length of room is considered to be longwall while the wall perpendicular to long wall is said to be short wall. To get thelength of long wall or short wall, calculate first the centre line lengths of individual walls. Then the length of long wall, (out to out) may be calculated after adding half breadth at each end to its centre line length. Thus the length of short wall Measured into in and may be found by deducting half breadth from its centre linelength at each end. The length of long wall usually decreases from earth work tobrick work in super structure while the short wall increases. These lengths aremultiplied by breadth and depth to getquantities. 2.CENTRE LINE METHOD This method is suitable for walls of similar cross sections. Here the totalcentre line length is multiplied by breadth and depth of respective item to get thetotal quantity at a time. When cross walls or partitions or verandah walls joinwith main all, the centre line length gets reduced by half of breadth for eachjunction. Such junction or joints are studied carefully while calculating total centreline length. The estimates prepared by this method are most accurate and quick. 3.PARTLY CENTRE LINE AND PARTLY CROSS WALL METHOD This method is adopted when external (i.e., around the building) wall isof one thickness and the internal walls having different thicknesses. In such cases,centre line method is applied to external walls and long wall-short wall method isused to internal walls. This method suits for different thicknesses walls and differentlevel of foundations. Because of this reason, all Engineering departments arepracticing this method.

Detailed Estimate Preparation: The preparation of detailed estimate consists of working out quantities of various items of work and then determines the cost of each item. This is prepared in two stages. A) DETAILS OF MEASUREMENTS AND CALCULATION OF QUANTITIES The complete work is divided into various items of work such as earth work concreting, brick work, R.C.C. Plastering etc., The details of measurements are taken from drawings and entered in respective columns of prescribed preformed. The quantities are calculated by multiplying the values that are in numbers column to Depth column B) ABSTRACT OF THE ESTIMATED COST: The cost of each item of work is worked out from the quantities that already computed in the details measurement form at workable rate. But the total cost is worked out in the prescribed form is known as abstract of estimated form. 4%of estimated Cost is allowed for Petty Supervision, contingencies and Unforeseen items. The detailed estimate should accompanied with I) Report ii) Specification iii)Drawings (plans, elevation, sections) iv) Design charts and calculations v)Standard schedule of rates. C) FACTORS TO BE CONSISDERED WHILE PREPARING DETAILED ESTIMATE i) Quantity and transportation of materials: For bigger project, the requirement of materials is more. such bulk volume of materials will be purchased and transported definitely at cheaper rate. ii) Location of site: The site of work is selected, such that it should reduce damage or in transit during loading, unloading, stocking of materials. iii) Local labor charges: The skill, suitability and wages of local labors are considered while preparing the detailed estimate. D) DATA

The process of working out the cost or rate per unit of each item is called as Data. In preparation of Data, the rates of materials and labor are obtained from current standard scheduled of rates and while the quantities of materials and labor required for one unit of item are taken from Standard Data Book E) FIXING OF RATE PER UNIT OF AN ITEM The rate per unit of an item includes the following: 1) Quantity of materials & cost: The requirement of materials is taken strictly in accordance with standard data book(S.D.B). The cost of these includes first cost,freight,insurance and transportation charges. 2) Cost of labour: The exact number of labourers required for unit of work and the multiplied by the wages/ day to get of labour for unit item work. 3) Cost of equipment (T&P): Some works need special type of equipment, tools and plant. In such case, an amount of 1 to 2% of estimated cost is provided. 4)Overhead charges: To meet expenses of office rent, depreciation of equipment salaries of staff postage, lighting an amount of 4% of estimate cost is allocated.

Preparation of Approximate Estimate Preliminary or approximate estimate is required for studies of various aspects of work of project and for its administrative approval. It can decide, in case of commercial projects, whether the net income earned justifies the amount invested or not. The approximate estimate is prepared from the practical knowledge and cost of similar works. The estimate is accompanied by a report duely explaining necessity and utility of the project and with a site or layout plan. A percentage 5 to 10% is allowed for contingencies. The following are the methods used for preparation of approximate estimates. A) PLINTH AREA METHOD: The cost of construction is determined by multiplying plinth area with plinth area rate. The area is obtained by multiplying length and breadth (outer dimensions of building). In fixing the plinth area rate, careful observation and necessary enquiries are made in respect of quality and quantity aspect of materials and labour, type of foundation, height of building, roofwood work, fixtures, number of storey's etc., As per IS 3861-1966, the following areas include while calculating the plinth area of building a) Area of walls at floor level. b) Internal shafts of sanitary installations not exceeding 2.0m2, lifts, air-conditioning ducts etc., c) Area of barsati at terrace level: Barsati means any covered space open on one side constructed on one side constructed on terraced roof which is used as shelter during rainy season. d) Porches of non cantilever type. Areas which are not to include a) Area of lofts. b)Unenclosed balconies. c) Architectural bands, cornices etc., d)Domes, to...