Method of Estimation

 

Estimate__ 

Before undertaking the construction of a project it is necessary to know its probable cost which is worked out by estimating, an estimating is a computation or calculation of the quantities required and expenditure likely to incurred, an estimating is a computation or calculation of the quantities required and expenditure likely to incurred in the construction of a work . the primary object of the estimate is to enable one to know beforehand, the cost of the work (building ,raod,structure ,….etc.), the estimate is probable cost of work and is determined theoretically by mathematical method of calculation based on the plans and drawing and current rates. Approximate estimate may be prepared by various methods but accurate estimate is prepared by detailed estimate method.

Actual cost

The actual cost of  a work is know as the completion of the work. Account of all expenditure is maintained day to day during the execution of work in the account section and at the end of the completion of the work when the account is completed , the actual cost is know.  The actual cost should not differ much from the estimated cost worked out at he beginning .

 

Detailed Estimate

 

Preparation of detailed estimate consists of working out of quantities of different items of work and then working out the cost.

The estimate is prepared in two stages:

 

1.       Detailed of measurement and calculation of quantities --- The whole work is divided into different item of the work  suck as earthwork,concrete,bricks, block, substructure work….etc.and the item are classified and grouped under different sub heads and details of ,measurement of each item of work are taken out and  quantities under each item are computed in prescribed form. Detailed of measurement form is given below.

2.       Abstract of estimate cost---  the cost under item of work is calculated from the quantities already computed at workable rate. And the total cost is worked out in a prescribed form, abstract of estimate form. A percentage of 3 to 5 per cent is added to contingencies, to allow for petty contingent expenditure , unforeseen expenditure ,change in design, change in rate.. etc.which may occur during the execution of work . a percentage of 1 to 2 percent is also added to meet the expenditure of work- charged establishment . the grand total thus obtained is the estimated cost of the work.  Abstract of estimate form is given below.

 

In the above form the description of each item should be such as to express exactly what work ,materials ,proportion of mortar….etc have provided for .

In preparing an estimate item are usually classified and grouped sub –head wise but for beginner it is continent to make   up the item in the same order as far as possible , as they would be executed or constructed . if the principle of following the order of construction from foundation to up ward direction is followed there is little chance of omission of items.

 

Main items of work

1-      Earth work---- earth work is excavation and earthwork in filling are taken out separately under different item, and quantities are calculated in cubic meter . foundation trenches are usually dug to the exact width of foundation with vertical side . earth work in excavation in foundation is calculated by taking the dimension of each trench width x length x depth. Filling in trench after the construction of foundation masonry is ordinary neglected. If the trench filling is accounted this may be calculated by deducting the masonry from the excavation .

2-      Concrete in foundation ---  the concrete is taken out in cu m by length x breadth x thickness . the length and breadth of foundation  concrete are usually the same as for excavation.only the thickness and depth is differs. The thickness of concrete is varies from 20cm to 45 cm, foundation concrete usually consist of lime concrete or weak cement concrete.

3-      Soling ---- when the soil is soft or bad , one layer of dry bricks or stone is applied before the foundation of concrete. The soiling layer completed in the sq m .

4-      Damp proof course---- D.P.C usually of 2.5cm thick rich cement concrete 1:1 ½:3 or 2cm .

5-      Masonry ---- Masonry is computed in cu m length x breath x height. Foundation and plinth masonry is taken under one item.and masonry in super structure is taken under separate item. In story building the masonry in each story as ground floor above plinth level, first floor ,second floor …etc is computed separately .in taking out of quantity the wall are measured as solid and then deduction are made for opening as door,window…etc.and such portion are necessary.

 DEDUCTION FOR OPENING ,BEARING ETC IN MASONRY

No deduction is made for following

1.       Opening each up to 1000 sq cm or 0.1 sq m

2.       End of beams ,posts, rafter,purlins etc upto 500 sq m or 0.05 sq m

3.       Bed plate ,wall plate ,bearing of chajjas  and like upto 10 cm depth.

Please click below link for sample

https://theworldpedias.blogspot.com/2022/07/boq-sample-bill-of-quantity.html