Can anyone please explain the long wall short wall and centre line method in detail?

archdevil

Royal Member
By the central line method estimate for earthwork, concrete work or brickwork for all walls of a whole building having the same section is estimated at a time. But for partition walls or walls of other section of the building attention is required to locate the junctions with the main wall in order to subtract half the width of the work of the main wall for each junction at the same level.


By long and short wall method each wall of a building is estimated separately. The long walls are considered out-to-out and short walls in-to-in. For in-to-in consideration attention is required to see the level with which the short wall joins with the long wall in order to deduct half the width of the work from each joint at the same level.


Thus, by Centre line method estimate of a building can be prepared quickly eliminating lengthy mathematical calculations. But the centre line of a building cannot be physically measured at site, where as the long and short walls i.e. out-to-out and in-to-in measurements of rooms of a building can be physically measured. So, Centre line method is preferred to prepare estimates and long and short wall method is preferred for entring measurements in the Measurement Book (M.B.
 

Alhaj Pathan

Apprentice
The quantities of various items such as excavation, foundation concrete, brickwork in foundation and plinth, brickwork in superstructure etc can be calculated by following methods:
  1. Centre line method
  2. Long walls and short walls method
  3. Crossing method
Centre line method :
In this method, sum of total length of centre lines of walls long and short, has to be found out. You can find quantities by multiplying the total centre length by the respective breadth and height. This method is quick but requires special attention and consideration at the junctions, meeting points of cross walls, etc.

Centre line length of one wall = Inner dimension of room + ½ wall thickness of one side + ½ wall thickness of other side

Lets understand this method by one simple example :
1510329061092.png

Lets assume thickness of wall 0.9 m

Centre line length of horizontal wall = 4 + 0.45 + 0.45 = 4.90 m
Centre line length of vertical wall = 3 + 0.45 + 0.45 = 3.90 m

Total length of centre line = 2 (4.90 + 3.90) = 17.6 m

Now Quantity of excavation for foundation = Total length of centre line of walls x breadth of trench x Depth of trench
= 17.6 x 0.9 x 1.2
= 19.01 m³


For rectangular, circular or polygonal buildings having no inter or cross walls, this method is quit simple but for buildings having cross or partition walls, for every junction of partition or cross walls with main walls, half breadth of the respective item or footing is to be deducted from the total centre length.
Therefor,
Net centre line length = Total centre line length - (½ x breadth of continuous wall x number of junctions)

Long walls and short walls method :
In this method, the longer walls in a building (generally in one direction) are considered as long walls and measured from out to out. The walls perpendicular to direction of long walls are considered as short walls and are measured from in to in . These lengths of long and short walls are multiplied separately by the breadth and height of the corresponding layer and are added to get the quantity. Such lengths of long and short walls vary in every layer of footing.

Lets take one example (Refer above figure) :

Length of long wall (horizontal walls) = 4 + 0.9 + 0.9 = 5.8 m
Length of short wall (Vertical walls) = 3 m (because in to in measured length)

Quantity of excavation for foundation = 2 x (5.8 x 0.9 x 1.2) + 2 x (3 x 0.9 x 1.2) = 19.01 m³