CHAPTER 1 Estimation PDF

**CHAPTER -1** **Introduction** **WHAT IS AN ESTIMATE......** Before taking up any work for its execution, the owner or builder should have a thorough knowledge about the volume of work that can be completed within the limits of his funds or the probable cost that may be required to complete th...

**CHAPTER -1** **Introduction** **WHAT IS AN ESTIMATE......** Before taking up any work for its execution, the owner or builder should have a thorough knowledge about the volume of work that can be completed within the limits of his funds or the probable cost that may be required to complete the proposed work. It is therefore necessary to prepare the probable cost or estimate for the proposed work from its plan and specification. Otherwise, it may so happen that the work has to be stopped before its completion due to the shortage of funds or of materials. Besides the above , an estimate for any public construction work is required to be prepared and submitted beforehand so that sanction of necessary funds may be obtained from the authority concerned. Thus an estimate for any construction work may be defined as the process of calculating the quantities and costs of the various items required in connection with the work. It is prepared by calculating the quantities, from the dimensions on the drawings for the various items required to complete the project and multiplied by unit cost of the item concerned. To prepare an estimate , drawing consisting of the plan , the elevation and the section through important points, along with a detailed specification giving specific description of all workmanship , properties and proportion of materials , are required. **PURPOSE OF ESTIMATING:-** To ascertain the necessary amount of money required by the owner to complete the proposed work. For public construction work, estimates are required in order to obtain administrative approval , allotment of funds and technical sanction. To ascertain quantities of materials required in order to programme their timely procurement. To calculate the number of different categories of workers that is to be employed to complete the work within the scheduled time of completion. To assess the requirements of tool , plants and equipment required to complete the work according to the programmed. 4 Estimation & cost evaluation-1 To fix up the completion period from the volume of works involved in the estimate. To draw up a construction schedule and programmed and also to arrange the funds required according to the programming. To justify the investment from benefit cost ratio.(for ideal investment ,this ratio should be more than one) To invite tenders and prepare bills for payment. An estimate for an existing property is required for valuation **TYPES OF ESTIMATE** ROUGH COST ESTIMATE PLINTH AREAESTIMATE CUBICAL CONTENT ESTIMATE A QUANTITY ESTMATE APPROXIMATE QUANTITY METHOD DETAILED OR ITEM RATE ESTIMATE REVISED ESTIMATE SUPPLEMENTARY ESTIMATE REPAIR AND MAINTENANCEESTIMATE A COMPLETE ESTIMATE **ROUGH COST ESTIMATE** IT is prepared to decide the financial policy matter.it is prepared on basis of practical knowledge and cost of similar works. The competent sanctioning authority accords "Administrative approval These estimates are also referred to as rom estimate and are useful for go /no kind decision making which essential refers to whether the project should or should not be pursued Some of the methods they can be useful for such estimates are investment per annual capacity turnover and capital ratio. **PLINTH AREA ESTIMATE** IT Is prepared on the basis of plinth area of the building multiplied by plinth area rate prevalent in the region. 5 Estimation & cost evaluation-1 Plinth area rates are fixed from the cost of similar buildings constructed in the locality having similar finishing's and amenities 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 labor, type of foundation, height of building, roof, wood work, fixtures, number of stores etc. **CUBICAL CONTENT ESTIMATE** This estimate is worked out on the basis of the cubical contents of proposed building to be constructed and then applying to it the rate per cubic meter. This is more accurate than plinth area estimate. The cubic content rates are deduced from the cost of similar buildings constructed in the same locality This method is generally used for multi-storied buildings. It is more accurate that the other two methods viz., plinth area method and unit base method. The cost of a structure is calculated approximately as the total cubical contents (Volume of buildings) multiplied by Local Cubic Rate. The volume of building is obtained by Length x breadth x depth or height. The length and breadth are measured out to out of walls excluding the plinth off set Under Review 6 Estimation & cost evaluation-1 **A QUANTITY ESTIMATE OR QUANTITY SURVEY** This is complete estimate or list of quantities for all items of work required to complete the concerned project. The quantity of each individual items of work is worked out form respective dimensions on the drawing of the structure to find the cost of an item in quantity is multiplied by the rate per unit from that item. The purpose of the bill quantity i.e. to provide a complete list of quantities necessary for the competition of any engineering project and when price given to the estimated cost of the project. **APPROXIMATE QUANTITIES** Regarded as the most reliable and accurate method of estimating, provided that there is sufficient information to work on. Depending on the experience of the surveyor, measurement can be carried out fairly quickly using composite rates to save time. The rules of measurement are simple, although it must be said; they are not standardized and tend to vary slightly from one surveyor to another. One approach involves grouping together items corresponding to a sequence of operations and relating them to a common unit of measurement; unlike the measurement for a bill of quantities, where items are measured separately Composite rates are then built up from the data available in the office for that sequence of operations All measurements are taken as gross over all but the very large openings Initially, the composite rates require time to build up, but once calculated they may be used on a variety of estimating needs Reasonably priced software packages are now available. An example for a composite is shown below for substructure: This is an approximate estimate to find out an approximate cost in the short time and thus enable the authority concerned to consider the financial aspect of the scheme for according sanctioned the same. Such an estimate is framed after knowing the rates of similar works and form practical knowledge in various ways for various types of work such as Plinth area or square meter method. Cubic rate or cubic meter method. Serve unit or unit rate method. 7 Estimation & cost evaluation-1 Bay method. Approximate quantities with bill method. Cost comparison method Cost from materials and labor. **DETAILED OR ITEM RATE ESTIMATE** This estimate is an accurate and is based on the plan and sanctions of the building. The quantity of items under each sub head of work are calculated from the dimensions taken from drawing and then total cost is worked out in a form called abstract of cost This include the detailed particulars for the quantities ,rate and cost of all the items involved for satisfactory completion of a project Quantities of all items of work are calculated from their respective dimension on the drawing on a measurement sheet.multiplying these quantities by their respective rate in separate sheet, the cost of all items of work are worked out individually and then summarized A detail estimate is accompanied by Report Specification Detailed drawing showing plane Design data and calculation Basis of rates adopted in the estimate **REVISED ESTIMATE** IT Is also a detailed estimate and is prepared a fresh when the original sanctioned detailed estimate exceeds by 10% or more ,either due to rates being found insufficient or due to some other reasons It is always possible that in spite of all precaution in the planning stages it becomes clearly during execution the actual cost of a project will exceed the original estimate ,now generally a certain cushion of the cost is available ,if the exceedance is higher It is prepared on the basis on estimate on which sanction was obtained showing the existing sanction and the progress made up to date The revised estimate should be accompanied by comparative statement showing the original and revised rate and quantity **SUPPLEMENTARY ESTIMATE** This is a fresh detailed estimate of the additional work in additional work in addition to the original one and is prepared when additional work is required to supplement the original work There is always a like hood that while executing a certain project it may be considered worthwhile to carry out additional work ,which was not foreseen in initial stages and therefore not actual for the preliminary estimate 8 Estimation & cost evaluation-1 Execution of such work required drawing up and approval of supplementary estimate and the exercise is essential similar to that of drawing up the estimate for the main work it is naturally expected that the cost of additional work will be much smaller than the main work In case where a substantial section of a project in abandoned or where material deviation from the original proposals are expected to result in substantial savings the estimate is revised by the department and intimated to engineer in charge for execution of work But in case where the saving is due to a material deviation of structural nature from the design originally approved supplement estimate is prepared for a revised technical sanction The method of preparation of supplementary estimate is the same as that of detail estimate and it should be accompanied by full report of the circumstances which render it necessity. The abstract must show the amount of original estimate and the total of sanctioned required including the supplementary amount.