Estimation is a process in which we calculate the expected expenditure of a project, which helps us to find the amount of fund that is to be spend in the project, in case the funds available are less, than the specification of work and property of work can be changed to match the funds available.
In building construction after making estimation we make bill of quantity so that the amount can be calculated that is to be spend in the construction work with the help of schedule of rate.
For calculating the estimation of building, firstly we divide the building into following parts:
1) Foundation part of the building
2) Sub structure part of the building
3) Super Structure part of the building
4) Finishing work of the building
5) Door & Window fitting work
6) Plumbing fitting work
7) Bill of quantity
1) Foundation part of the building: In this part we read the structural drawing of centre line in which footing detailing are given with the help of that data is abstracted. After that we start estimation with the first construction step of any building that is site cleaning, we calculate the area of the site that is to be cleaned and then calculate the volume of material that is to be excavated and after that the amount of Sand filling is calculated in volume and then plain cement concrete is calculated which we provide on the bottom of the foundation in the excavation pit, then the volume of foundation is calculated with the form work then the volume of pedestal column is calculated among with formwork after that backfilling is done and the amount can be calculated in volume.
2) Sub structure part of the building: In this part of building firstly we calculate the amount of one line brickwork in cubic metre and then the volume of ground beam concrete is calculated and then the shuttering of ground beam is also calculated after that we calculate the brickwork up to DPC bottom in cubic metres after that we calculate the quantity of damp proof course in square metres and then we provide and calculate residual coat of Bitumen in square metres and then plinth filling is done and the amount is calculated in cubic metres after that we provide flooring of plain cement concrete and then we provide Column of substructure and calculate the volume in cubic metres.
3) Super Structure part of the building: In this part of building firstly we calculate one line brickwork for super structure for 200 mm wall and 100 mm wall as well and calculate the quantity of the respected wall in cubic metres and square metres after that we provide damp proof course above the one line brickwork and the quantity is calculated in square metres then brick work up to sill band bottom is calculated in square metres and cubic metres for 100 mm and 200mm wall as well after that we provide sill band concrete below the window then we calculate the amount of sill band concrete in cubic metres after then we calculate the shuttering of sill band and then we provide brickwork up to lintel beam bottom and calculate the amount for 100 mm and 200 mm wall in square metres and cubic metres as well then lintel beam is provided throughout the building and the quantity is calculated in cubic metres after then the amount of formwork is calculated which is used in lintel beam concrete then brickwork up to slab beam bottom is calculated for 100 mm and 200 mm wall in square metres and cubic metres respectively after that slab beam concrete is provided and the quantity is calculated in cubic metres after then the amount of shuttering is also calculate it which is lying in slab beam and then the amount of slab beam concrete is calculated in cubic metres and the shuttering is also calculated in square metres which is lying below the slab after then we calculate the amount of staircase concrete in cubic metres and the formwork of staircase is also calculated in square metres then column for superstructure is provided and the amount is calculated in cubic metres the formwork is also calculated for column in square metres.
4) Finishing work of the building: In this part of building, we provide plaster work on the wall for smooth surface and there is three types of plaster are provided that is 6mm plaster, 12mm plaster and 15mm plaster as well. 6mm plaster is provided in the ceiling of slab. 12mm plaster is provided in the inner walls and 15 mm plaster is provided on the outer walls of the building. The quantities of these items are calculated in square metre. After the plastering work white wash are provided above the plastered surface and the amount is calculated in square metres after the process of white wash putti is provided on the outer walls, inner walls and ceiling as well. The amount is calculated in square metres. After then we provide inner paint to the interior walls of the building and outer paint to the outer walls of the building and the amount it is calculated in square metres respectively. After than we provide flooring work to the building different types of flooring are provided in a building to increase the aesthetic view you and appearance of the building some of the famous flooring examples are vitrified tiles, ceramic tiles, Marble work, Granite stone etc. All these floorings are implemented according to the drawing and the mode of measurement of all the flooring work are in square metres.
5) Door & Window fitting work: In this part of building, we provide different type of doors and window to the building and the specification of door in window is according to drawing we read drawing then the data is abstracted and then different quantities are calculated.
Firstly, the amount of door frame is calculated in cubic metres except the FRP door frame the amount of FRP door frame are calculated in running metre according to schedule of rates. After calculating volume of frames, the amount of door shutter is calculated in square metres. After then amount of door fitting items are counted from the drawing and the values are inserted in the Excel after the completion of door fitting work, we calculate the amount of aluminium window and window grill as well. Aluminium window is calculated by dividing it into two parts the first one is the window frame that is to be fitted in the wall and the second one is the sliding frame which is inside the window frame after that we calculate the quantity of window grill according to drawing and the unit of measurement is taken in kilograms.
6) Plumbing fitting work: In this part of building different type of fittings of plumbing are calculated the mode of measurements of major part of the plumbing items enumerated quantities. We calculate the plumbing fitting items according to drawing and the drainage items are also calculated and the pipes which are used in plumbing fitting are calculated in in running metre there are many types of pipes are used in plumbing work some of them are galvanized iron pipe, polyvinyl chloride pipe, chlorinated polyvinyl chloride pipe, un-plasticized polyvinyl chloride pipe. The length of these pipes is calculated according to the drawing.
7) Bill of Quantity: This part is the most important part of building estimation because till now we are calculating the quantities not the amount but from now we are able to calculate amount of each item by multiplying the quantities to the rates which we get from the schedule of rate. And hence we get the amount of all the quantities and when we add these amounts then we get the bill of all the quantities that's why the result of estimation is known as bill of quantity.
The process is very simple we read the schedule of rate and find various items which we previously calculated and hence we get the rate from the schedule of rate after multiplying the rates to the quantities then we get the total amount of various items of our building estimation.
Bill of quantity is very important document which we use in in different part of construction industry that's why it is necessary to understand the process of making bill of quantity to each and every engineer working in this industry.
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