1 Estimation and Costing Chapter 1 INTRODUCTION TO THE SUBJECT 1.1 DEFINITION OF ESTIMATING AND COSTING Estimating is the technique of calculating or Computing the various quantities and the expected Expenditure to be incurred on a particular work or project. In case the funds avilable are less than the estimated cost the work is done in part or by reducing it or specifications are altered, the following requirement are necessary for preparing an estimate. a ) Drawings like plan, elevation and sections of important points. b) Detailed specifications about workmenship & properties of materials etc. c) Standard schedule of rates of the current year. 1.2 NEED FOR ESTIMATION AND COSTING 1. 2. 3. 4. 5. Estimate give an idea of the cost of the work and hence its feasibility can be determined i..e whether the project could be taken up with in the funds available or not. Estimate gives an idea of time required for the completion of the work. Estimate is required to invite the tenders and Quotations and to arange contract. Estimate is also required to control the expenditure during the execution of work. Estimate decides whether the proposed plan matches the funds available or not. 1.3 PROCEDURE OF ESTIMATING OR METHOD OF ESTIMATING. 1. 2. 3. Estimating involves the following operations Preparing detailed Estimate. Calculating the rate of each unit of work Preparing abstract of estimate 1.4 DATA REQUIRED TO PREPARE AN ESTIMATE 1. 2. 3. Drawings i.e.plans, elevations, sections etc. Specifications. Rates.
Introduction to the Subject 2 1.4.1 DRAWINGS If the drawings are not clear and without complete dimensions the preparation of estimation become very difficult. So, It is very essential before preparing an estimate. 1.4.2. SPECIFICATIONS a) General Specifications: This gives the nature, quality, class and work and materials in general terms to be used in various parts of wok. It helps no form a general idea of building. b) Detailed Specifications: These gives the detailed description of the various items of work laying down the Quantities and qualities of materials, their proportions, the method of preparation workmanship and execution of work. 1.4.3. RATES: For preparing the estimate the unit rates of each item of work are required. 1. For arriving at the unit rates of each item. 2. The rates of various materials to be used in the construction. 3. The cost of transport materials. 4. The wages of labour, skilled or unskilled of masons, carpenters, Mazdoor, etc., 1.5 COMPLETE ESTIMATE: Most of people think that the estimate of a structure includes cost of land, cost of materials and labour, But many other direct and indirect costs included The Complete Estimate and is shown below. Cost of land Actual cost of land Cost of Surveying P.s.and contingencies at 5% Cost of Verification of deeds and execution of deeds Cost of Structure Legal expenses between owner and contractor Brochorage if any Cost of labour cost of materials Permit fees for constrution water, electricity from concerned autorities Consulting Engineers fees cost for preparation of plan, estimate and design Cost of supervision
3 1.6 LUMPSUM: Estimation and Costing While preparing an estimate, it is not possible to workout in detail in case of petty items. Items other than civil engineering such items are called lumpsum items or simply L.S.Items. The following are some of L.S. Items in the estimate. 1. Water supply and sanitary arrangements. 2. Electrical installations like meter, motor, etc., 3. Architectural features. 4. Contingencies and unforeseen items. Ingeneral, certain percentage on the cost of estimation is alloted for the above L.S.Items Even if subestimates prepared or at the end of execution of work, the actual cost should not exceed the L.S.amounts provided in the main estimate. 1.7 WORK CHARGED ESTABLISHMENT: During the construction of a project considerable number of skilled supervisors, work assistance, watch men etc., are employed on temporary basis. The salaries of these persons are drawn from the L.S. amount alloted towards the work charged establishment. that is, establishment which is charged directly to work. an L.S.amount of 1½ to 2% of the estimated cost is provided towards the work charged establishment. EXERCISE Short Answer Questions 1. State the requirements of an estimate? 2. Briefly Explain need for estimation? 3. What is work charged establishment?
4 Chapter 2 MEASUREMENT OF MA TERIALS MATERIALS AND WORKS 2.1 UNITS OF MEASUREMENTS: The units of measurements are mainly categorised for their nature, shape and size and for making payments to the contractor and also. The principle of units of measurements normally consists the following: a) Single units work like doors, windows, trusses etc., are expressed in numbers. b) Works consists linear measurements involve length like cornice, fencing, hand rail, bands of specified width etc., are expressed in running metres (RM) c) Works consists areal surface measurements involve area like plastering, white washing, partitions of specified thickness etc., are expressed in square meters (m2) d) Works consists cubical contents which involve volume like earth work, cement concrete, Masonry etc are expressed in Cubic metres. [BASED ON IS 1200 REVISED] Sl. No. I II Particulas of item Earth work: 1. Earth work in Excavation 2. Earthwork in fillingin foundation trenches 3. Earth work in filling in plinth Concrete: 1. Lime concretre in foundation 2. Cement concrete in Lintels 3. R.C.C.in slab 4. C.C. or R.C.C. Chujja, Sunshade 5. L.C. in roof terracing (thickness specified) Units of Measurement Units of payment cum cum Per%cum Per%cum cum Per%cum cum cum cum cum percum percum percum percum sqm persqm