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ESTIMATING COSTING

by Karthika SampathkumarKarthika Sampathkumar
Type: PracticalInstitute: Anna university Course: B.Tech Specialization: Civil EngineeringOffline Downloads: 6Views: 576Uploaded: 6 months ago

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Karthika Sampathkumar
Karthika Sampathkumar
Estimation and Valuation Practices Academic Year - 2017-18 ESTIMATION AND VALUATION PRACTICES INTRODUCTION “What is the purpose and necessity of studying this subject?” This is the first question which arises in mind. The answer lies in the following questions:(a) Has one got enough money to spend on the construction? (b) Has one got ample time that one can wait for the completion of the construction? (c) Has one got resources that one can arrange any amount of desired material to be used in construction? If the answer is YES, then the study of this subject is useless. But if the answer is NO, then the question arises, “which are the factors necessitating the study of this subject.” Any person indulged in the Civil Engineering profession can clearly think of these factors i.e. set amount of funds, costly labour ( skilled and unskilled), difficulty in getting good building materials, particularly cement and day to day rising cost of steel, bricks, timber etc. Also economy and standard of the construction are two important things required. Standard of construction can be achieved by careful supervision and selecting proper specifications whereas for Economy, planning is a must. The total quantity of various materials used in construction, if known before hand, can help the planning towards economy. TYPES OF ESTIMATES The estimates may be divided in to the following categories:(1) Preliminary or Approximate estimate. (2) Rough cost estimate based on plinth area. (3) Rough cost estimate based on cubic contents. (4) Detailed estimate. (5) Annual repair estimate. (6) Special repair estimate. (7) Revised estimate (8) Supplementary estimate. Page 5 of 95
Estimation and Valuation Practices Academic Year - 2017-18 1. Preliminary or Approximate estimate This estimate is prepared to decide financial aspect, policy and to give idea of the cost of the proposal to the competent sanctioning authority. It should clearly show the necessity of the proposal and how the cost has been arrived. The calculations for approximate estimate can be done with the following data. The data can be had from a similar construction already complete in the nearby area, executed by the department. For example: To calculate approximate estimate for a Hospital, per bed cost is calculated from the recent completed hospital and is multiplied with the number of beds required. Similarly for a house, per square meter plinth area is calculated and is multiplied with the proposed covered area. The specifications should also be same. For a road, expenditure of per kilometer length is taken, width also plays the role. The following documents should be attached with it. (a) Detailed report (b) Site plan of the proposal (c) It should also clearly mention about the acquisition of land, Provision of electric and water supply etc. 2. Plinth area Estimate (Based on Rough Cost) Plinth area of a building means Length x Breadth (roofed portion only ) excluding plinth offsets. The estimates are prepared on the basis of plinth areas of the various buildings proposed to be constructed. The rates are being arrived at the dividing the total cost of construction with its plinth area. For example if total cost of a building is Rs. 2 lac and its plinth area is 50 sq. m. then plinth area rate =2,00,000 = Rs.4000/- per 50 sq.m. Using this rate as basis of the next construction, approximate or rough cost of the proposal can be arrived at by multiplying the plinth area of the proposed building with this plinth area rate. The following documents are attached with the estimate. (a) Line plan with brief specifications. (b) Cost of various services added i.e. electric and water supply etc. (c) North line should be shown clearly on line plan. Page 6 of 95
Estimation and Valuation Practices Academic Year - 2017-18 3. Cubic Contents Estimate (Based on Rough Cost) The cubic contents of a building means plinth area x height of the building. The height is taken from top of floor level to top of roof. The cubic contents of the proposed building are multiplied with cubic rates arrived at for the similar construction i.e. total cost of construction divided by cubic contents = cost per cubic meter. Documents attached are as in No. 2 (Administrative approval is granted on rough cost estimate) 4. Detailed Estimate After getting Administrative approval on rough cost estimate, detailed estimates are prepared. In this, the estimate is divided in to sub-heads and quantities of various items are calculated individually. In the end of the detailed quantities, an abstract of cost giving quantities of each item and rate of every item according to the sanctioned schedule of rates shall be attached. In case of non-schedule rates i.e. rates which are not given in the sanctioned schedule of rates, proper analysis of rates shall be attached. If however the work proposed to be constructed is located in a remote place, the provision for the carriage of the material shall be added in the estimate to avoid any excess over the administratively approved estimate later on. Detailed specifications & report should also be attached with the estimate. Technical sanction is given on detailed estimate. The detailed estimate shall also provide for the cost of approach road, water supply, electric installations and acquisition of land etc, so as to call it a comprehensive estimate. 5. Annual repair estimate In order to keep building and roads in perfect condition, annual repairs should be carried out as follow:(i) In case of a building-white washing, oiling and painting of doors and windows, cement plaster repairs (inside & outside), repairs of floors etc. In no case this annual repair amount should increase more that 11/2% to 2% of the capital cost of the building. (ii) In case of a road-filling patches, maintenance of beams etc. 6. Special repair estimate If the work cannot be carried out of the annual repair funds due to certain reasons resulting in the genuine increase in cost, then special repairs estimate is to be prepared. The reason of increase may be:(i) In case of a building-opening of new doors, change of floors, replastering walls etc. Page 7 of 95
Estimation and Valuation Practices Academic Year - 2017-18 (ii) In case of roads-if the whole surface is full of corrugation & patches, then the total surface is to be scarified. The old metal is taken out, consolidation by adding more metal is done and top surface is repainted. 7. Revised estimate When the sanctioned estimate exceeds by 5% either due to the rate being found insufficient or due to some other reasons, a fresh estimate is prepared which is called a Revised Estimate. A comparative statement on the last page of the estimate is attached giving there in the reasons of the increase of cost in case of each item. 8. Supplementary Estimate This is fresh detailed estimate in addition to the original sanctioned estimate prepared when additional works are deemed necessary during the progress of a work to supplement the original works. The abstract of cost should show the amount of the original sanctioned estimate as well as the supplementary amount of the original sanctioned estimate as well as the supplementary amount for which sanction is required. METHODS OF TAKING OUT ESTIMATES The calculations of quantities of materials can be done using various methods of estimates. The application of an individual method depends upon the design and shape of the building. The different methods are as under: 1. Centre line method. 2. Crossing method. 3. Out to out and in to in method. 4. Bay method. 5. Service unit method. 1. Centre line method This method is suitable only if the offsets are symmetrical and the building is more or less rectangular in shape. The centre line of the building is determined carefully after doing deductions for repeated measurements (as explained in the next problem). This centre line acts as length for the complete calculations of the estimate. If the deduction is not cared for the results of estimates may be wrong. All the walls should have the same section. Page 8 of 95

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