Different methods for estimating buildings works

1. Long and short wall or ‘out-out’ & ‘in to in’ method or P.W.D method

2. Centre line method

 3. Crossing method

1. ‘Long and Short wall’ or ‘out-to-out’ & ‘in-to-in’ 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; and the shorter or partition walls, in a normal direction of the long walls, are considered as short walls and are measured from in-to-in for a particular layer of work. 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.

To calculate the lengths of long and short walls determine first their centre to centre lengths individually from the plan. Then the length of the long wall, out-to-out may be calculated after adding half breadth of the wall at each end to its centre to centre length. Thus the length of the short wall measured in-to-in may be found out after subtraction of half breadth at each end from its centre to centre length. The length of the long wall generally decreases from earthwork to brickwork in the superstructure and in case of the short wall, its length increases. Thus the length of the long wall is found out by adding one breadth of the footing to the centre to centre length of that footing. The length of the short wall is found out by subtracting one breadth of the footing from the centre to centre length.

In some of the working examples, it may be noticed that a wall is considered as a short wall at one end and as a long wall at the other end. Such a case arises in a wall which joins as a long wall with another long wall previously considered. The joining end of the wall later considered as long wall is actually treated as a short end, such a wall is termed a Long-Short wall.

2. Centre line method:

In this method calculate the total centre line length of walls in a building and multiply the same by the breadth and depth of the respective item to get the total quantity at a time. For different sections of walls in a building, the centre line length for each type shall be worked out separately of the breadth of the layer of the main wall that connects with the partition or verandah wall at the same level. A number of such joints are studied first to calculate the centre line length.

By this method, estimates may be prepared more quickly and this method is as accurate as of the other methods. Only in this case of an unsymmetrical wall which is generally rare, no advantage may be claimed by this method over others as the centre line length varies at every layer. But to estimate circular, hexagonal octagonal, etc shaped building this method is especially useful.

3.Crossing Method:

In this method calculate the overall perimeter of the building and subtract from this, four times the thickness of the wall to obtain the centre line length.

Internal walls are grouped individually to their sections and measured between the internal faces of the main wall at that level.

Principally this method is the same as the centre line method but differs in the process of calculation to find the centre line lengths.

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