Estimate is the method for finding out the quantity of various construction item and materials which are used in construction work. The required dimensions, length, breadth and depth or height, are to be taken out from the drawings i.e. plan, elevation and sections. When you start construction estimate you will study the drawing and imagine the building pictured in your mind and the dimensions are to be taken correctly.
Image Courtesy – Cloudfront
There are a number of cost estimation methods for calculating the quantities like earthwork, foundation, concrete, brickwork in plinth and superstructure but mainly below two methods are used:
- Long wall and short wall method
- Centre line method
Here we discuss long wall and short wall cost estimation method.
Long Wall and Short Wall Method
For the calculating quantity of various construction item, long wall and short wall method is used. For measuring the long wall and short wall the external out-to-out length of walls running in the longitudinal direction generally is considered as “long wall” while the in-to-in internal length of walls running in the transverse direction is called as “short wall” or “cross wall”. For calculating quantity multiply the length into the breadth and height of the wall.
As shown in the figure we indicate long wall and short wall and centre line is indicated with red line.
For finding out the length of long wall, simply add centre length of wall to the two times half breadth on one side of the wall which gives the out-to-out length of long wall.
Length of Long Wall = Center to Center Length of wall + Half Breadth on One Side + Half Breadth on the Other Side
= Center to Center Length of wall + One Breadth
For finding out length of short wall or cross wall subtract from the centre length, so the one breadth of the wall, which gives the length of the short wall (in-to-in) (instead of adding).
Length of Short Wall = Centre to Centre Length – One breadth
Note: The length of the long wall usually decreases from earthwork to brickwork, and the length of the short wall is increased.
Here we give example of long wall and short wall method.
Using the above image, you can first find the length of long wall and short wall.
Centre to Centre length of long wall = 5+ (1/2×0.30) + (1/2 x 0.30) = 5.30 m
Centre to Centre length of short wall = 4+ (1/2 x 0.30) + (1/2×0.30) = 4.30 m
After finding out the length of the long wall and short wall, now find the quantity of the various items which are used in construction.
You can calculate the quantity of various construction items using the above method for different building dimension.
Long wall and short wall method is used for finding out the quantity and cost of materials. This method is simple and accurate, so there is may be no chances of any mistake. But correctly choose long wall and short wall for finding out accurate quantity.