ESTIMATION_AND_COSTING assignmentt-1.pdf
- 2. CONTENT • Introduction to estimating and costing • Importance of estimating • Purpose of estimating • Data required for estimating • Types of estimates • Rate analysis • Terms used in rate analysis • Provision and purposes of different charges • Terms used in estimates • Unit of measurement for various construction activities
- 3. INTRODUCTION OF ESTIMATING AND COSTING • Estimating and costing are closely the same things. The estimate is defined as the process of calculating the various quantities and the expected expenditure to be incurred on a particular work or project. The estimate gives the probable cost of work. • The primary objective of an estimate is to enable one to know the probable cost of the work before the completion of the project. If the estimate is prepared carefully and correctly there will not be much difference between estimated and actual cost.
- 4. IMPORTANCE OF ESTIMATING • The estimate is necessary for fixing the budget for the purposed project. • It is necessary to calculating the required quantities of materials and laborers for the project. • It is necessary to draw up a work schedule. • It is necessary to fix up the completion period of the proposed project. • It is also helpful to check the works done by contractors during and after the execution. • It is required for preparing tenders for the project. • It is necessary for the valuation of land and building.
- 5. PURPOSE OF ESTIMATING • To estimate the probable cost of the work. • To find the various types and quantities of material required. • To find the various categories and quantities of labors required. • To give an idea of the time required for completion of the work. • To justify investment from benefit-cost ratio. • To help in fixation of standard rent and valuation of properties.
- 6. DATA REQUIRED FOR ESTIMATING • Drawing – plans , elevation, sections, etc. • Specifications • Rates • Methods of measurements
- 7. • DRAWING 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. • 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) 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.
- 8. • 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 labor, skilled or unskilled of masons, carpenters, Amador, etc.
- 9. TYPES OF ESTIMATES • The construction cost estimates can be prepared either in a detailed manner by taking into consideration item by item or can be calculated approximately without going much into the details. Based on these criteria, there are mainly 8 cost estimates followed in construction: ❑ Approximate or Preliminary estimate ❑Plinth area estimate ❑Cube rate estimate ❑Detailed estimate ❑Revised estimate ❑Supplementary estimate ❑Annual repair estimate.
- 10. ❑ APPROXIMATE OR PRELIMINARY 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 (example: 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).
- 11. PURPOSE OF PRELIMINARY OR APPROXIMATE ESTIMATE • Preliminary study of the projects. • Administrative approval • To investigate feasibility • For insurance purpose • For deciding charge • Tp decide rent for building
- 12. ❑ PLINTH AREA ESTIMATE • As the name implies, this estimate is prepared by multiplying the plinth area of the proposed building by the plinth area rate of similar building having same specifications and height that is constructed very recently in the same locality. • The plinth area of the proposed building is calculated for the covered i.e. roofed portion by measuring the outer dimensions at the plinth level. • The area of courtyards, and other open areas are not to be included while calculating the plinth area. • The plinth-area method of preparing estimate gives the approximate cost of the building to be constructed.
- 13. ❑ CUBE RATE 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.
- 14. ❑ DETAILED ESTIMATE • Detailed estimate is prepared by finding out the actual quantities of different items of the work and then multiplying the cost of per unit item. Sum of the cost of each item and add to it suitable percentage of work charge establishment and contingencies, Etc. • Following are different sheets use to find quantities, cost per unit item , etc. Measurement sheet Abstract sheet General abstract sheet
- 15. RATE ANALYSIS • Determination of rate per unit of a particular item of work from the quantities and cost of materials , labors etc. required is termed as rate analysis. • Determination of rate depend upon : 1. Market rates of materials 2. Transportation of material 3. Labors involved in construction 4. Contractors profit ( 10% )
- 16. ANALYSIS OF RATES HAVE TWO HEADS AND THREE SUB- HEADS 1) Cost of material 2) Cost of labors 3) Plans and equipment 4) Contractors profit 5) Overheads charges
- 17. TERMS USED IN RATE ANALYSIS • Task work : the quantity of work done by labor in a day is termed as task work . • Lead : it is the horizontal distance from center of area of excavation to the center of placed earth. • Lift : it is the vertical distance through which the excavated soil is lifted. • Schedule of rates : it is the list of rates for common items of works and it is prepared by an engineering department in form of printed bool lets. Due to changes in market , it is necessary to revised the rates for every years.
- 18. PROVISION AND PURPOSES OF DIFFERENT CHARGES • Contingencies charges : The miscellaneous incidental expenditure which cannot be specified in any specific item , is specified as contingencies charges. the provision of 3% to 5% of the estimated cost of work is shown as contingencies charges. • Work charge establishment : during the construction of civil engineering work, some supervisory staff like supervisor, watchmen etc. to be appointed on temporary basis. The payment of such staff are made from work charge establishment . The provision is about 2% to 3% of estimated cost. • Quality control charges : number of tests can be conducted with special equipment to ensure desired quality of work. About 0.5% of the estimated cost of work is provided.
- 19. • Centage charges : sometimes one department undertakes the work of other department ( local bodies ) . Generally 10% to 15% of estimated cost. • Electrification charges : the provision for electrification charges is about 5% to 8% of estimated cost of work provided. • Water supply charges : the provision of water supply ( plumbing ) charges about 8% of estimated cost of work is provided. • Sanitary charges : the provision for sanitary charges or drainage charges is about 8% of the estimated cost pf work is provided.
- 20. TERMED USED IN ESTIMATES • Prime cost : the details of certain items such as doors and windows fittings , water supply and sanitary fittings, types of handrails, electrical fittings, etc. are not shown in drawing. The details of such items are not work out at time of preparing estimate but provision is made for these items as a lumpsum amount in the estimate. This is known as prime cost or prime cost sum. • Provisional sum : some items of works which are special like installation of air conditioners, lifts, etc. such items of work cannot be carried out by civil engineer, therefore a certain amount of sum of money is included in the estimate. This amount is known as provisional sum. • Lumpsum : when it is not possible to decide a suitable unit rate for items of works and it is difficult to measure the work in standard units, the provision is made up in lumpsum basis in estimate. Such provision is known as lumpsum provision. Ex. Site clearance, dewatering, dismantling of structure.
- 21. • Provisional quantities : Works which are not shown in detailed drawing like quantities of excavation, foundation concrete , etc. cannot be estimated before knowing the sub soil information. The quantities of such items are measured at sites as per drawing. An extra provision for additional quantities for these items is made in estimate as a provisional quantities. • Extra items : Such items occurs due to happenings at he site, changes in the drawing, design and specification and addition, alteration suggested during execution these items are not cover in contract agreement. • Spot items : those items which is not possible to fix the amount in the estimate without observing and studying on the spot like site clearing of the site, demolition of structure, connecting old existing structure with neat structure, dewatering, etc.
- 22. UNIT OF MEASUREMENT FOR VARIOUS CONSTRUCTION ACTIVITIES • The unit of measurements for any construction activities depend on the nature of work being done, shape and size. They are determinant of quantities of work being done. • Following are main principles for measuring units : ▪ Measurements is based on the finished item of work with detailed description of it. ▪ Following order should be maintained : length, breadth, height/thickness. ▪ Least dimensions should be: ▪ 0.01m in length ▪ 0.01m2 square feet in area ▪ 0.01m3 in volume ▪ 0.001 tons in weight