Introduction to Estimation | Estimation, Costing and Supervision-I

 

1.1         Definition of Estimate

                  The process of calculating approximate cost and quantities of various items required in construction work, for satisfactory completion is known as Estimation.

1.2         Importance of Estimate

 

(a)  Estimate given idea of cost the work.

(b) Estimate is necessary to determine the quantities of construction work.

(c)  It is done for the administrative approval for public work.

(d) It is also necessary on property valuation work.

(e)  It prepares bill of quantities and bill for payment.

(f)   Estimate is also required to control the expenditure during the execution of the work.

(g) It is required for the preparing tenders for the project.

(h) It is necessary to find the number of worker, tools and equipment for the completion of the project.

(i)    The estimate is necessary for fixing the budget for the project.

1.3         Types of Estimate

·       Preliminary Estimate

·       Detailed Estimate

·       Revised Estimate

·       Supplement Estimate

·       Revised and supplement Estimate

·        Complete Estimate

·       Cube area Estimate

·       Plinth area Estimate

·       Repair and Manitenance Estimate

Explain:

(a)Preliminary Estimate

                             The estimate is generally prepared initial stage to known the approximate estimate calculate by comparing the previous experience or similar type of project.  It is used to obtain administrative approved. It is also called rough estimate or approximate estimate.

(b)          Plinth area Estimate

 

                             Plinth area estimate by multiplying plinth area of building with plinth area rate. In this method plinth area should be calculate by taking internal dimension of the building at the plinth level.                                                                     Plinth area estimate = Plinth area*plinth area rate

(c)  Revised Estimate

                           It is detailed estimate and is prepared a fresh, when the original sanction detailed estimate exceeds by 5% or more, either due to rates being found the sufficient or due to some other reasons.

(d)          Cube area estimate

                                       In this method the cost of structure is calculated approximately as the total cubical content (volume of building) multiplying by local cube rate. It is more suitable for multi-storied building. This method of estimate is accurate than plinth area estimate.

(e)          Detailed estimate/Item rate estimate

                          The estimate is an accurate and is based on the plan sanction of the building. The quantities of item under each sub-head of the work are calculates from the dimension taken from drawing and then total cost is work out on from called abstract cost. The rate of different item of work area taken as per schedule or rate or analysed rates for finished item of work. A percentage 3 to 5% as add as contingency for unseen item ad 2 to 3% is added as work charge establishment.

(f)   Revised Estimate

                           It is detailed estimate and is prepared a fresh, when the original sanction detailed estimate exceeds by 5% or more, either due to rates being found the sufficient or due to some other reasons.

(g)  Supplementary Estimate

                            This is fresh detailed estimate of the additional work in additional one and prepared when the additional work is required to supplement the original work.

(h) Repair and maintenance Estimate

                             The estimate are prepared in order to maintain the constructed structure in good condition. Work that are considered repair estimate may be white washing, painting, plastering work, patching work etc.