Long Wall And Short Wall Method Of Estimation
There are two methods of quantity estimation for walls: the long wall & short wall method and the centre line method. The pre-contract estimation of the building is necessary for floating the tender and estimating the preliminary budget of the project.
This estimation is done based on tentative drawings. Further, post-tender estimation includes the calculation based on the detailed drawings.
The estimation helps in estimating the type of works to be done in building, their material requirement, and budget. The long wall & short wall method divides the walls into two types. The bifurcation is based on the inclusion and exclusion of corners.
The wall that includes the corner is called a long wall and the wall that excludes the corner is known as a short wall. Since the corners and joints form the basis for the bifurcation, hence special care should be taken in calculating the length of walls.
In the present, we shall calculate the brickwork and plaster quantity by the long wall & short wall method of estimation. Also, we shall estimate the material quantity for the same.
Drawing Study & Observations
Let us study the drawing and draw our observations.
It is clear from the drawing that Wall 1 & Wall 2 are long walls as both of them include the corners. Wall 3, Wall 4 & Wall 5 are short walls.
- The thickness of the pedestal 1st step = 0.6 m
- The thickness of the pedestal 2nd step = 0.6 m
- The thickness of the pedestal 3rd step = 0.5 m
- Height of Wall above plinth level = 3 m The Thickness of wall = 0.4 m
- Length of Wall 1 = 5 m Length of Wall 2 = 5 m
- Length of Wall 3 = 5 – 0.4 – 0.4 = 4.2 m
- Length of Wall 4 = 5 – 0.4 – 0.4 -1.2 = 3.0 m Length of Wall 5 = 4 m
Calculations For Brickwork
Cross Section Area
First, let us calculate the area of the pedestal and wall. We can later calculate the volume of the work by multiplying the cross-area section and length.
Area of Pedestal = Area of 1st Step + Area of 2nd Step + Area of 3rd Step
- = 1.5 x 0.6 + 1.2 x 0.6 + 1 x 0.5
- = 0.9 + 0.72 + 0.5 = 2.12 m2
Area of Wall = Width of wall x Thickness of wall
- = 0.4 x 3 = 1.2 m2
Total Area = Area of Pedestal + Area of Wall
- = 2.12 + 1.2 = 3.32 m2
Volume Of Brickwork
Volume of Wall 1 = Total Area x Length of Wall 1
- = 3.32 x 5 = 16.6 m3
Volume of Wall 2 = Total Area x Length of Wall 2
- = 3.32 x 5 = 16.6 m3
Volume of Wall 3 = Total Area x Length of Wall 3
- = 3.32 x 4.2 = 13.94 m3
Volume of Wall 4 = Total Area x Length of Wall 4
- = 3.32 x 3 = 9.96 m3
Volume of Wall 5 = Total Area x Length of Wall 5
- = 3.32 x 4 = 13.28 m3
Total Volume of work = 16.6 + 16.6 + 13.94 + 9.96 + 13.28
- = 70.38 m3
Calculations For Plaster
Internal Plaster –
Internal Area of W1 = Wall length x Wall Height
- = (5 – 0.4 – 0.4) x 3 = 12.6 m2
Internal Area of W2 = Wall length x Wall Height
- = (5 – 0.4) x 3 = 13.8 m2
Internal Area of W3 = Wall length x Wall Height
- = (5 – 0.4 – 0.4 – 0.4) x 3 = 11.4 m2
Internal Area of W4 = Wall length x Wall Height
- = (5 – 0.4 – 0.4 -1.2) x 3 = 9.0 m2
Internal Area of W5 = Wall length x Wall Height
- = (4 + 4 + 0.4) x 3 = 25.2 m2
Total internal area for plaster-
- = 12.6 + 13.8 + 11.4 + 9 + 25.2 = 72 m2
External Plaster –
External Area of W1 = Wall length x Wall Height
- = 5 x 3 = 15.0 m2
External Area of W2 = Wall length x Wall Height
- = 5 x 3 = 15.0 m2
External Area of W3 = Wall length x Wall Height
- = 5 x 3 = 15 m2
External Area of W4 = Wall length x Wall Height
- = (5 – 1.2) x 3 = 11.4 m2
Total external area for plaster = 15 + 15 + 15 + 11.4 = 56.4 m2
Material Estimation
Brickwork
Assuming the brickwork is done with standard size bricks (190 mm x 90 mm x 90 mm) with cement mortar of 1:6 (1 cement and 6 coarse sand).
It is known that for 1 m3 of brickwork, 500 nos. standard-sized bricks are required. Cement and sand requirements are 1.33 bags and 408.25 kg per m3 of 1:6 mortar.
Bricks = Volume of brickwork x No. of bricks per cum
- = 70.38 x 500 = 35190 Nos.
Cement = Volume of brickwork x No. of cement bags per cum
- = 70.38 x 1.33 = 93.60 bags
Sand = Volume of brickwork x Weight of coarse sand per cum
- = 70.38 x 408.25
Plaster = 28732 kg
The assuming the internal plaster to be 12 mm thick and exterior plaster to be 20 mm thick. The grade of plaster is to be 1:6 (1 cement and 6 fine sand).
It is known that 1 m2 of 12 mm thick plaster needs 0.8 bag cement and 250.7 kg fine sand. Also, 1 m2 of 20 mm thick plaster needs 1.33 bags of cement and 417.86 kg fine sand.
Cement = Cement for internal plaster + Cement for external plaster
- = 72 x 0.8 + 56.4 x 1.33 = 132.61 bags
Fine Sand = Sand for internal plaster + Sand for external plaster
- = 72 x 250.7 + 56.4 x 417.86 = 41617.7 kg
Summary of Material Required
Cement = Cement for brickwork + Cement for plaster
- = 93.60 + 132.61 = 226.21 bags
Bricks = 35190 Nos.
Coarse Sand = 28732 kg
Fine Sand = 41617.7 kg
Also Read
Center Line Method Of Estimation
Types Of Estimates In Construction
What Is Approximate Estimation?
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