Estimation, Theory, Long Wall Short Wall Problem of Building Construction

ESTIMATION

Estimation is the probable cost of any project or work which is prepared before the execution of work or project.

Estimation is the process of calculating the cost of various items involved in the work by calculating the quantity of various items and considering the local prevailing rates of the item.

The main object of estimation is that it is necessary to justify the investment required for the execution of any work. If the estimated cost is more than the fund available, then it becomes necessary to reduce the volume of work or else it becomes necessary to change the specification of various items involved in the project.

The actual cost of the project comes to know after the completion of project. The estimation of project shall be prepared such that the estimated cost must be very nearer to the actual cost of project.

Data required for Estimation :

To prepare the estimate of any project, the following data is required.

1. Detailed drawings such as plan, elevation and important sections and also structural drawings.
2. Scheduled Rates
3. Specification of various items

Application or necessity of Estimation :

1. Estimation of any project is required for the justification of investment.
2. From the Estimation, the Quantity of different items are worked out and with the help of these quantities of items, the quantity of different material for different items can be worked out.
3. By knowing the quantities of various items and output of labor, the number of skilled labor and unskilled labor required to execute that work can be calculated.
4. From the Estimation, the completion schedule time of project can be worked out.
5. To call the tender and to prepare the tender notice and to allocate the work to the contractor, estimation of the project is required.

Methods of Estimation :

There are two  methods of Estimation.

1. Long Wall and Short Wall method
2. Center Line Method

1. Long Wall and Short Wall Method :

In this method by studying the entire plan, the plan is divided into Long Wall (LW) and Short Wall (SW). Generally the Long Wall measured are taken in one direction and measured out to out. Hence a wall measured out to out is called as Short Wall.

In the Estimation of structure using Long Wall and Short Wall method, he following steps has to be followed.

• Divide the entire plan into number of LW & SW as per convenient and designate them. Walls which are having different length or foundation details are to be designated separately. (Such as LW1, LW2, LW3 etc and SW1, SW2,SW3 etc)
• Calculate Centre to Centre length of all long wall and short wall with reference  to plan

i.e, c/c length of long wall = (length of long wall in that direction) + (half of thickness of wall on one end) + (half of thickness of wall on other end)

and

c/c length of short wall = (length of short wall in that direction) + (half of thickness of wall on one side) + (half of thickness of wall on other side)

• Actual length of long wall is obtained by adding half of the width of an item on either side to the calculated center line length.

• The actual length of short wall is obtained by deducting half width of an item on one side and half width of an item on other side.

• These actual calculated length are multiplied with depth and width of the respective item.

Estimation of Earthwork, C.C. Bed Single Stone Masonry, CRS Masonry, DPC, Brick Masonry for Single Room using Long Wall Short Wall Method

1. Earthwork in Excavation
2. C.C. Bed 1:4:8 in Foundation
3. Single Stone Masonry or Size Stone Masonry in Cement Mortar 1:6
4. CRS Masonry 1:6 in Plinth
5. 2.5cm Thick DPC 1:2:4
6. Brick Masonry for Super Structure in Cement Mortar 1:4