Sunday, June 25, 2017

Introduction and Approximate Estimates

 

 

 

 

 

 

Introduction and Approximate Estimates

 

 

 

 

By

Sudarshan Sampatrao Bobade

Assistant Professor

Department of Civil Engineering

PCET’s PCCOER, Ravet

Pune- 412101

 

 

 

 

Unit I

Introduction and Approximate Estimates                                                      [6 Lectures]

a)      Introduction to estimates and related terms:

Definitions of estimation and valuation:

Estimation:

Ø  A rough calculation of the value, number, quantity, or extent of something.

Ø  A judgment of the worth or character of someone or something.

Valuation:

Ø  An estimation of the worth of something, especially one carried out by a professional valuer. "it is wise to obtain an independent valuation"

Ø  The monetary worth of something, especially as estimated by a valuer.

Significance (application) of the Course:

This course covers the various aspects of estimating of quantities of items of works involved in buildings, water supply and sanitary works, road works and irrigation works. This also covers the rate analysis, valuation of properties and preparation of reports for estimation of various items. At the end of this course the student shall be able to estimate the material quantities, prepare a bill of quantities, make specifications and prepare tender documents. Student should also be able to prepare value estimates.

Purpose of estimation:

Ø  To have an Idea of overall construction cost

Ø  Estimation for Public construction is needed to have and administrative approval, technical sanction and funds

Ø  For timely procurement of materials as per the estimated quantities

Ø  To make a construction programme and prepare schedule

Ø  To set the deadlines for various construction activities

Ø  Determine requirement of tools, equipment and plants

Ø  To arrange the labour as per work

Ø  For Inviting tenders and prepare bills

Ø  To measure benefit cost ratio

Ø  For an existing, estimate is required for Valuation

 

 

 

 

Type of estimates, data required for estimation as a pre requisite.

*      APPROXIMATE ESTIMATE –

It is also called budget, preliminary estimate. This type of estimate is prepared in the initial stage of a project. To give a clear idea to the owner (client) about the amount of cost needed for the project and to get the approval from necessary sanctioning bodies (eg: from banks to get loan). Documents such as project drawing plans, details about the land including electricity & water supply and a full clear report are necessary to carry out the estimate. Commonly the approximate estimate is calculated with relevant to the previous experience.eg: To calculate the estimate for a house, a previously (& also recently) completed similar house will be considered. Here the estimator already knows the rate for 1m2 area & with that he/she calculates the cost estimate for the newly proposed area (of similar house).

Approximate estimate = Rate of 1m2 (already known value) X proposed area (m2)

*      PLINTH AREA ESTIMATE –

Plinth area estimate can be achieved by multiplying the values of plinth length, plinth width & plinth area rate. Here the plinth area is referred as, external plinth area of the building at floor level. Simply it can be also stated as the roof covered area of a building. Plinth area rate is derived by dividing the total cost of a previously constructed building by plinth area of the previously constructed building.

Plinth area estimate = Plinth area X plinth area rate.

Plinth area = plinth length X plinth width

Plinth area rate = Total cost of a previously built building / Total plinth area of that building.

There are some restrictions in calculating the plinth area of a building and some area have to include or exclude when calculating. Among that, areas which can include are,

Floor area with area of walls at floor level excluding the offsets of the building, internal shafts of sanitary fittings within 2m2, lifts, air conditioning ducts, area of porch at floor level (cantilever part can’t be included), area of barsati – a room on the terrace or roof top with veranda outside.

Areas which can’t include are,

Area of lofts, open balconies / un enclosed balconies, fascia, towers which project above terrace level, louvers & vertical sun breakers.

Documents such as line plan with complete specifications & costs for services such as water, electricity should be attached with estimate.

Meaning of an item of work, and enlisting the items of work for different Civil Engineering projects.

*      CUBIC CONTENT ESTIMATE –

This type of estimate done by multiplying the volume of the building by the unit cubic rate achieved from the previously (also recent) estimate. This type of estimate is a little bit more accurate than above mentioned methods and mostly suitable for multi storied buildings. Here the cost of corbelling (corbel – a piece of stone, wood, brick, or other building material, projecting from the face of a wall and generally used to support a cornice or arch), cornice and other works like that are neglected.

Cubic content estimate = Volume of the building X unit cubic rate (known value)

Volume of the building = plinth area (length X breadth of the proposed building) X height of the building (floor to roof top)

Unit cubic rate = total cost of the previously built building / total volume of that building.

*      ANNUAL REPAIR ESTIMATE AND SPECIAL REPAIR ESTIMATE –

These estimates are prepared in order to maintain the constructed element in good condition.  Works that attached when consider repair works, white washing, painting, plastering works, patching works & etc. Special repair estimate is prepared in situations where the costs of materials increased when compare to annual repair estimate cost.

*      REVISED ESTIMATE-

This estimate is prepared when the rate of previously submitted estimate increases by 5% or more than that. But here the reason for the preparation of estimate must have a strong & valid reason like sudden increase in cost of materials. The reason and comparative statement between 2 estimates should be annexed with the revised estimate.

*      SUPPLEMENTARY ESTIMATE –

This type of estimate is prepared when there is a necessary situation of supplementary work, to progress out the original work. The annexure of originally prepared estimate & supplementary estimated amount of the originally prepared estimate when submitting for requesting approve.

*      DETAILED ESTIMATE-

Detail estimate is prepared with the help of complete set of contract documents. The preparation of detailed estimate can do under 2 phases such as work out with quantities of different works and calculate the cost of each work.

1) work out with quantities of different works – The whole construction work procedure is divided into categories such as excavation and earthwork, concrete work, formwork, reinforcement, masonry work, roof covering and roof plumbing, carpentry, painting and decorating, plumbing, electrical installation and etc.

 

The measurement takeoff procedure is done with the help of drawings/plans and then they are entered in measurement. Measurement sheet is a prescribed form which contains number of columns to enter the respective measurements and descriptions about the works. Finally the measurement columns are multiplied to get the necessary quantity.

2) Calculation of the cost of each work – The already obtained quantities is used to obtain the cost of each work. Calculated costs of each work item are summarized in order and that document is called as abstract sheet.

A detailed estimate should have documents such as report, specifications, drawings/plans, design charts and schedule of rates. Factors such as, material quantity, transportation of materials, location of site, labour charges, cost of equipment (commonly allowed: - 2% of the estimated cost), overhead charges (commonly allowed: - 2% of the estimated cost), contingencies & unforeseen (commonly allowed: - 4% of the estimated cost) items are needed to consider well while preparing the detailed estimate.

Note:  The rate used to estimate should check with current standard schedule of rates & in case of quantity, it should check with standard data book.

Units of measurement:

What is Unit?

The unit of measurement for any construction activities depends on the nature of work being done, shape and size. They are determinant of quantities of work being done. Following are the main principles for measuring units:

1.      Measurement is based on the finished item of work with detailed description of it.

2.      Following order should be maintained: Length, Breadth, Height/Thickness.

3.      Least dimensions should be:

a)      0.01m in length

b)      0.01 m2 Sqft in area

c)      0.01 m3 in volume

d)     0.001 tons in weight

 

 

 

 

 

 

 

Mode of measurement of building items/ works:

1.      Earthwork: It is measured in CUM or m3. This includes all types of excavation. Vegetation removal and other extra work are measured separately.

2.      Backfilling: It is measured in CUM or m3. This includes all types of filling work (generally the excavated material). Vegetation it is measured removal and other extra work is measured separately.

3.      Brickwork: It depends on how the bricks are laid.

4-Inch Brick work: It is measured in SQM or m2.

8-Inch Brick work: It is measured in CUM or m3.

* There should be no deductions for small openings like pipe holes for scaffolding and openings less than 0.1 Sqm.

4.      Stonework: Stonework is measured in CUM or m3.

* There should be no deductions for small openings like pipe holes for scaffolding and openings less than 0.1 Sqm.

5.      Concrete work: Reinforced Cement Concrete: It is measured in CUM or m3.

Plain Cement Concrete: It is measured in CUM or m3.

Plum Concrete: It is measured in CUM or m3.

Chip Packing: It is measured in RMT or m.

* There should be no deductions for volume of pipes or conduits smaller than 0.01 Sqm, volume of reinforcement bars and openings less than 0.1 Sqm.

6.       Tile Flooring: It is measured in SQM or m2. It involves floor or wall tiling and any other types of tiling work.

7.       Weathering Course: It is measured in SQM or m2.

8.       Brick Bat Coba: It is measured in CUM or m3.

9.       Plastering: It is measured in SQM or m2. Plaster work which is less than 30 cm in width will be measured in RMT. Openings smaller than 0.5 Sqm should not be deducted.

10.   Painting: It is measured in SQM or m2. Openings smaller than 0.5 Sqm should not be deducted. It involves white washing, colouring, varnishing, Distempering.

11.   Drip, string course and water coping: It is measured in RMT or m.

12.   Glazing: It is measured in SQM or m2. Polishing and Rounding is measured in RMT.

13.   Formwork: It is measured in SQM or m2. Openings smaller than 0.4 m2 should not be deducted.

14.   Centering & Shuttering: It is measured in SQM or m2. Openings smaller than 0.4 m2 should not be deducted.

15.   Scaffolding: It is measured in SQM or m2 (if Height more than cum). Openings smaller than 0.4 m2 should not be deducted.

16.   Door/ Window Framing: It is measured in Numbers.

17.   Hume Pipe Installation: It is measured in RMT or m. And Rate will change with Diameter This involves installation and testing.

18.   Waterproofing work: It is measured in SQM or m2.

19.   Hacking/ Roughening: It is measured in SQM or m2.

20.   Fixing GI Mesh: It is measured in RMT or m.

21.   Damp Proof Course: It is measured in SQM or m2.

22.   Dismantling: It is measured in CUM or m3 & Sqm. m2 Both Depend upon Item.

23.   Steel Work:

Steel bars in RCC work: It is measured in Quintal.

Bending/ Binding of steel: It is measured in Quintal.

Rivets and Bolts: It is measured in Quintal.

Iron Railings/ Grills / Insert Plate : It is measured in Quintal.

24.   Pointing: It is measured in SQM or m2. Pointing work which is less than 30 cm in width will be measured in RMT. Openings smaller than 0.5 Sqm should not be deducted.

25.   Piping: It is measured in RMT or m.

 

 Introduction to components of estimates:

Face Sheet

Sr. No.

Particulars

Amount

01

Estimated cost

Rs…….

02

Water supply and sanitary charges @... %

Rs…….

03

Electrification charges @...%

Rs…….

04

Contingencies @... (3 to 5 %)

Rs…….

05

Work charge establishment @ (1 to 2 %)

Rs…….

 

Total Amount

 

 

In words

 

 

Abstract sheet (BOQ):

Sr. No.

Quantity

Description or Particulars of Items

Unit

Rate

Unit of Rate

Amount

 

 

 

 

Rs

P

 

Rs

P

1

2

3

4

5

6

7

 

Measurement Sheet:

Item No.

Description or Particulars of Items

Number

Length

Breadth

Height or Depth

Quantity

Total Quantity

1

2

3

4

5

6

7

8

 

 

 

 

Rate Analysis:

Rate Analysis can be defined as the analytical study (qualitative and quantitative) that leads to the definition of a new unit rate referring to a given job or work type, by identifying its basic elements.

Lead statement:

The distance between the source of availability of material and construction site is known as "Lead” and is expressed in Km. The cost of conveyance of material depends on lead. This statement is required when a material is transported from a distant place, more than 8kms (5 miles). The lead statement will give the total cost of materials per unit item including first cost, conveyance loading-unloading, stacking charges etc.

A typical lead statement is provided as follows:

Sr. No.

Material

Unit

Cost at Source (Per Unit)

Lead in Km

Conveyance Charges (per km/per unit)

Total Conveyance Charges (per/unit)

Total Cost (In Rs./Per unit)

1

Rough stone

Cum

250.00

25

5

125

375

2

 

 

 

 

 

 

 

 

Provisional sum & Prime cost items:

Prime Cost

A prime cost is defined as ‘an item that has not been selected, or whose value is not known, at the time a domestic building contract is entered into and for the cost of supply and delivery of which the builder must make a reasonable allowance in the contract’

What this essentially means is that these are items that may not be selected yet – usually fixtures and fittings such as handles, stovetops and tapware – as it’s too early in the process. In order to ensure a consistent cost, the builder will make allowances for these items without knowing the specific cost. This allowance will include any mark-up or profit from the builder, as well as sourcing and installation costs.

Provisional Sums

A provisional sum is defined as ‘an estimate of the cost of carrying out particular work (including the cost of supplying any materials needed for the work) under a domestic building contract for which a builder, after making all reasonable enquiries, cannot give a definite amount at the time the contract is entered into.’

 

This translates to works that the builder cannot accurately price at the time of contract signing, like landscaping. It still includes both the provision of materials and the labour costs.

Most simply, prime cost applies to items themselves, provisional sums refers to complete works.

Contingencies:

The term `contingency’ represents any incidental or miscellaneous character that cannot be classified under any distinct item sub-head, yet pertain to the work as a whole. Contingencies in civil engineering are important while preparing estimate of any construction project. While planning any construction project, finalizing a budget is one of the major steps in planning a successful project. Designing and planning to project considering where to spend money and budgeting for all the work takes both attention to detail and the complete scope of the project. However, all estimate is correct and accurate there is some unforeseen issues or items that come up where additional work will be needed. This is where a contingency budget becomes critical. Contingencies in estimation and costing are an amount added in the total estimate to balance incidental and miscellaneous expenses.

What is the Amount of Contingencies Added?

To meet such unforeseen expense in construction contingency estimates an additional amount of 3 to 5% of the estimated cost of the work is provided in the total estimates. Miscellaneous incidental expenses that cannot be classified under any subhead item, are met the amount provided under contingencies. For estimating contingency is considered as 3 to 5 % of the total estimated cost of the project.

Examples of Contingencies in Construction

There is an item of work cement plastering in a 1:3 mix ratio with a neat cement finish, but during execution, it is desired to provide nosing at the end of steps. As there is no allocation of funds for this small work, the cost of sub work may be met up from the contingency fund.

In case when expenditure is required for any intermediate design change or due to an increased volume of work, and who cannot be covered from the contingency fund, supplementary or revised estimate submitted for its sanction before taking up the work.

If there is any saving against the amount provided under contingencies amount may be utilized with the sanction of the competent authority, to meet expenses of extra items of work.

The provision for contingencies may not be diverted to ray new work or repair which is not provided in the estimate and of which cost exceeds Rs. 2000 without the sanction of superintending engineer.

 

List of Contingency Items in Construction

The Following is list of contingency Items in construction,

*      Extra work which is added after starting of work

*      Any correction after work started

*      Item whose cost cannot be calculated in advance

*      Any mistake during constriction

Types of Contingency in Construction

Following are construction contingency examples and types used in construction.

1. Contractor Contingency

A contractor contingency is a fund into the contractor’s anticipated price for the project to account for various risk factors that cannot otherwise be accounted for in a schedule of values. This money is set aside to account for any errors that occur on behalf of the contractor. Accordingly, contractors consider these funds spent money.

 Adding this extra fund to the estimated cost of the project is the contractor accepting the fact that unpredictable costs are all part of the construction biz. Construction contingency is important before executing any project.

2. Owner Contingency

An owner’s reserve is an amount set aside for additions or modifications of the scope of the work. Owner contingency main utilized in guaranteed maximum price (GMP) contracts. Changes and mistakes are not always the contractor’s fault. Any changes that are not included in estimate or bid will have to be paid by the owner funded contingency. Incomplete plans or owner directed changes are the leading causes of dipping into an owner contingency fund.

Work charge establishment:

The work changed establishment will include the temporary establishment as are employed for the execution or the immediate technical supervision or departmental stores in connection with the specific work.

Work charged staff may be technical person or an under staff of technical person to assist him at work site, guard, etc. But work charged staff does not include non-industrial employees such as the typist, draftsman, clerk, etc.

Every payment made to a member of the work charged establishment whether on account of his wages or actual travelling expenses is charged to the work estimate on which they are employed. For such work charged establishment an amount of 1.5% to 2% (according to P.W.D.) of the estimated cost of the works is provided in the estimate.

Generally, the work charged persons are employed on monthly basis or temporary basis according to the progress of work. Their services lasts for the sanctioned period but may be continued on fresh sanction. Their services are terminable by one month’s notice for one year continuous service. But for less than one year service, 14 days’ notice is required to terminate their services.

Centage charges:

Centage Charges means in connection with a work which the Government execute on behalf of another Government, a local body or a private party.

Introduction to D. S. R.

The Schedule of Rates (Volume – I) is divided into two sections, Section -I for works, Section -II for materials & Labour and each section into sub-sections. In all cases of contracts in respect of Building Works, this entire volume of Schedule will be operative. Though this entire volume of Schedule is divided for convenience into sections and sub-sections it is to be taken as a whole. An item under one section will apply equally to work falling under the category of another section unless a similar item appears in the later section. The same principle applies to items under different sub-sections.

The ‘Engineer-in-Charge’ shall mean the Executive Engineer of the Division concerned. The Sub Divisional Officer concerned is authorized to carry out on behalf of the ‘Engineer-in-Charge’ general supervision, day to day instructions with approval of materials and workmanship. In case of dispute, the decision of the ‘Engineer-in-Charge’ shall be final and binding.

 Except when specifically mentioned in the description of the item itself, the rate for any item of work will apply equally to all floors, in any position and up to any height. In respect of concrete work etc. where the rate is on the basis of volume, the item shall apply to all cases irrespective of the thickness unless a specific item appear in the Schedule for the particular type of work. The work up to a particular floor level means all work up to the roof of that floor. All works in basement shall be treated as work in first floor for payment.

 Renewal works include dismantling and taking out of old works with mending good damages after renewal and removal of waste materials. The rate for any item of original nature not provided in this Schedule may be deduced from the rate of similar item of renewal work by multiplying by a factor 100/105 and conversely the rate of any item of renewal nature not provided in this Schedule may be deduced from the rate of similar item of original nature by multiplying by a factor 105/100.

 White washing, painting etc. include preparation of surface (including plugging old nail holes etc.) prior to the treatment and removal of all marks or stains from walls, floor, glass, panes, chowkats etc. For repair works, this also includes shifting and/or covering furniture etc.

 All works shall be carried out with due regard to the convenience of the occupants, if any, and the arrangement and programme of work must be adjusted accordingly. In case of works within Jails, Hospitals etc. the Rules & Regulations of Authorities concerned must be strictly obeyed. The rates given in the Schedule are deemed to be inclusive of all such factors and contingencies.

 All materials, tools and plants are to be arranged for the work. All labours (Skilled & Unskilled) including their housing, sanitation, procurement of food stuff, medical aids etc. are to be arranged by the contractor. Cost of transport of labour, materials and all other relevant items shall have to be borne by the contractor.

 Arrangement of water for preparation of concrete & mortar as well as for soaking of bricks and other materials are to be made by the contractor. Construction of platforms and vats including cost thereof are to be borne by the contractor.

If not specifically indicated in the items themselves, the rates appearing in this schedule are inclusive of cost of all supply, carriage, handling, fitting, fixing, toll charges, ferry charges etc. and all other incidental works involved in any floor, at any level including all necessary jointing materials, scaffolding to any height, hire charges of tools and plants, and all ancillary materials but exclusive of GST.

To arrive at complete rate of different items in this Schedule, 1% Sundries, 1% water charges, 5% overhead and 10% contractor’s profit have been considered along with the aforesaid material cost, labour cost and other cost etc.

Unless specifically mentioned otherwise in the description of the item itself, no extra charges will be paid for scaffolding (including stage scaffolding), centering, shuttering, curing etc. and the rates are deemed to be inclusive of the same for the satisfactory completion of the work.

 All materials brought to site must have approval of Engineer-in-Charge. Rejected materials must be removed by the contractor from the site within 24 (twenty-four) hours of the issue of orders to that effect. In case of non-compliance with such orders, the ‘Engineer-in-Charge’ shall have the authority for removal of those rejected materials at the cost and expenses of contractor and the contractor shall not be entitled to any loss or damage on that account.

 Departmental materials (i.e. materials are supposed to be issued by the department) shall be issued to the contractor to the extent of requirements as assessed and in small installments as decided by the Engineer-in-Charge. Issue of departmental materials may be of two categories :

(A) Materials for which value are to be recovered from the contractor.

(B) Materials which are issued directly to work (in respect of items the rates of which do not include the cost of these materials).

For materials under Category (A) the value of materials issued to the contractor on usual hand receipt shall be recovered from the bill of contractor in one installment or in successive installments as may be decided by the Engineer-in-Charge.

For materials under Category (B) the contractor will act as custodian of the department, when he shall take charge of the materials against appropriate receipts signed by him. The contractor shall remain responsible for the proper storage and safe custody of such materials. The rates of relevant items of work shall be deemed to be inclusive of reasonable consideration for such duties and responsibilities as the custodian.

All materials, whatever is the category thereof, shall be properly stored by the contractor in suitable godowns within the site of work. Under no circumstances, whatsoever shall any materials is removed from the site of work without prior written permission from the Engineer-in-Charge. The contractor shall be responsible for any damage or loss of such materials unless he can satisfy the Engineer-in Charge that the reasons for such damage or loss are due to circumstances beyond his control. The contractor shall also have to satisfy the Engineer-in-Charge regarding the proper utilization of such materials.

The value of any materials, which cannot be satisfactorily accounted for, shall be recovered from the contractor’s bill or other dues as specified in P. W. Department’s Order No. 2809(3)-A Dated 27.04.1971 as mentioned in West Bengal Form No. 2911.

Any materials under Category (A) which may be surplus in few quantities on completion of the work may at the sole discretion of the Superintending Engineer be taken back provided the same are found of non-perishable nature and has not been damaged in any way. Surplus materials under Category (B) shall be returned to the Engineer-in-Charge in good condition.

 Subject to the aforesaid condition, the following materials under Category (A) shall be issued to the contractor at issue rates reflected against each. The materials shall be issued from the departmental godown or godowns and for this purpose a stack-yard shall also be deemed as godown as may be specified in the contract stipulations for any particular work. The contractor will have to carry the materials at his own cost and his quoted rate will be deemed to be inclusive of all such costs including costs for loading, unloading and stacking.

i) Cement: Issue Rate and Basic Price of Cement are shown in Table – 1-1 of Annexure – I. If cement is supplied by the Department, the cost of cement will be recovered on Issue Rate, when in case of supply of the same by the contractor, then rates of those cement related items are to be deduced as per Format – A of Annexure - I. Except M35 & M40 Grade of design mix concrete, rates of all other cement related items have been derived considering PSC/PPC Cement. For M35 & M40 Grade of design mix concrete, OPC (Grade – 43/53) cement has been considered in deriving the item-rates.

ii) Reinforcing Steel: Issue Rate and Basic Price of Reinforcing Steel are shown in Table – 1-1 of Annexure – I. If Steel is supplied by the Department, the cost of Steel will be recovered on Issue Rate, when in case of supply of the same by the contractor, and then rates of those Steel related items are to be deduced as per Format – B of Annexure - I. Cut pieces of reinforcing steel materials left surplus on completion of work shall not be taken back if the same be considered as unsuitable for utilization in other works. Item-rates of structural steel and GCI Sheet have been derived considering said materials to be supplied by the contractor.

iii) Empty Bitumen Drum: - Prevailing Schedule of Rates (Volume – III) of PWD is to be followed. If in the interest of the work, materials other than those mentioned above are to be issued under Category (A), the issue-rate of such materials shall be based on the-then market rate or the stock issue-rate whichever is higher. Such issue-rate shall be decided by the Engineer-in-Charge and his decision shall be binding.

 Materials obtained by dismantling Government structures or parts thereof shall remain the property of Government. The contractor shall sort out and stack the serviceable materials within the premises and also dispose of the unserviceable rubbish etc. as per instruction of the Engineer-in-Charge or his representative.

The contractor shall remain the custodian of such dismantled materials till the charge of the same is taken over by the Engineer-in-Charge or his representative.

 The site must be cleared by the contractor from time to time by removing rubbish, debris etc. as accumulated during the work and on completion the whole site must be left in a clean and tidy condition to the satisfaction of Engineer-in-Charge or his representative.

 Number of full bricks salvaged by dismantling all types of masonry part of the structure must correspond to at least 20% of the volume dismantled.

 Carriage of materials (unless specifically considered in the Rate Analysis) is the sole responsibility of the contractor for which no extra payment should be made (unless in exigency a few of those seem to be justified by the Engineer-in-Charge, when the same are to be approved by the concerned Superintending Engineer).

Approximate Estimates:

An approximate estimate is an approximate or rough estimate prepared to obtain an approximate cost in a short time. For certain purposes the use of such methods is justified.

Meaning:

The approximate estimation is done in order to find out an approximate cost in very short time before starting the project. The estimation is made before selecting the final specification and design of the project. The method is also known as Preliminary or Rough Estimation.

Purpose:

Ø  To evaluate the cost of project in very short time.

Ø  To evaluate difference between several options

Ø  To check the final cost of the project that is calculated by detailed estimation

Methods of approximate estimation

1.      Square meter or Plinth Area Method:

This rough estimation is done by selecting the price of 1 square meter area of building. It is mainly adopted for calculating the cost of the following buildings:

a)      Office Buildings

b)      Residential Buildings

c)      School buildings

d)     Apartment/ Flat Buildings

e)      Hospitals

The method is considered as the best method for calculating the cost of the new buildings.

In case of multi - storeyed building, the following assumptions are to be considered for estimation.

a)                  For one square meter area, the cost of all the floors with basement and the roof are in equal costs

b)                  The cost of the basement is 60% of the floor.

c)                  The cost of the roofs is 40% of the floors.

2.      Cubic Rate or Cubic Meter or Cubic Content Method:

For multi storeyed buildings, the following assumptions are considered.

a)      For one meter cube area the costs of all floors are equal in costs.

b)      The cost of basement is 60% of the cost of different floors.

The volume of the floor is determined as:

Volume of the floor = Area X Height of One Floor

The Height of the floor is found out by the following guidelines:

1.      Ground Floor: The height of the ground floor is calculated from the top of the footing to the middle of the parapet

2.      First Floor: The height of the first floor is calculated from ground rooftop to the middle of the parapet.

3.      Other Floors: The height of other floors are calculated from floor to floor

Besides these methods, there are some other rough estimation methods such as

1.      Cost Comparison Method

2.      Unit Rate Method

3.      Approximate quantities with the bill method

4.      Bay Method

 

 

Other Civil Engineering Projects

Method of preparation approximate estimate for road projects

To prepare an approximate estimate Reconnaissance survey a narrow strip of all the possible routes between selected termini is conducted to determine the best possible routes and the approximate cost of the projected line.

The following information are collected from reconnaissance survey –

a. Extent of waterway for nallah and river crossings.

b. High flood level (H.F.L.) to determine the height of the road embankment.

c. Number and length of more important bridges.

d. Total length of the alignment.

e. Probable amount of earthwork.

f. Geological characteristics of the areas to determine foundations of bridges and stability of embankment.

g. Value of land.

In order to arrive at a fairly close estimate preliminary survey along a route or routes selected as a result of reconnaissance survey is conducted to determine the various distances, heights and angles.

From the above survey reports, maps and data preliminary estimates are prepared per km basis by adding the following heads.

Ø  Earth work estimate which includes provision of borrowed and hauling earth. Approximate estimate may be prepared with the help of contour map.

Ø  Cost of road structures includes cost of bridges and culverts. The spans of the structures are determined and an approximate estimate is found by multiplying the span by cost per meter span of the respective structures of items numbers.

Ø  Cost of sub-base, consisting of soling and edging according to the nature of the soil is selected and worked out for road width per km.

Ø  Cost of base course including premix carpet is estimated from the cost per km basis.

Ø  Cost of boundary pillars Rs.100 L.S. per km.

Ø  Contingency 15 % and W.C. 5 % are added to the total cost from heads (a) to (e).

Irrigation/ water supply:

Approximation estimate of irrigation project is prepared for storage reservoir, canals and dams. Approximate estimate is prepared on the basis of per million cubic meters of storage capacity or per square meter of catchment area for storage reservoir and dams.

For irrigation channels per km basis, depending on the capacity of the channel or per hector basis.

i.                    Approximate cost of 5 km long irrigation channel of 4 cum capacity @ 10 lakh is 50 lakhs.

ii.                  Approximate cost of 1000 hectors of command area @ 7000 is 70 lakhs.

Sanitary and Water Supply Works:

For sanitary and water supply works 8% of the estimated cost of works are generally provided.

Sanitary engineering:

i.                    On the basis of per head of population served

ii.                  On the basis of area covered

Example:

Ø  Approximate cost of sewage project for a population of 100000 @ Rs. 750/- per head work out to be Rs. 750 lakhs

Ø  Approximate cost of water supply project for a population of 50000 people @ 500 per head works out to Rs. 2.5 Cr

Electrical works:

For electrification 8% of the estimated cost of work is generally provided.

            Electrical wiring shall be measured in points such light point, fan point, plug point.

Classification: Point wiring shall be classified according to the length of wire as follows:

Ø  Short Points: Up to 3 m in length

Ø  Medium: 3 to 9 m in length

Ø  Long: 6 to 10 m in length

Ø  Special Points: more than 10 m in length

posted by Sudarshan @ June 25, 2017   0 Comments