Estimation For Variations

Variations become necessary during the construction of a structure. Variations may be necessary due to the following reasons. 

1. user intends to introduce changes in the structure, and 
2. changes in assumptions made at the time of design and drawing, e.g, foundation depth or foundation strata may differ during the construction. 

Variations may take one or more of the following forms: 

1. additional work, 
2. deletion of work, and 
3. alteration or replacing an existing item by a new item. 

Cost of the work will change due to variation. It is necessary to estimate the change in the cost due to the introduction of variation. Construction supervisor can play a very user role in estimation of change in the cost.This is done as follows: 

i)  Additional Work 

Cost of additional work will be extra cost to be added to the cost of the work originally approved. Items of additional work are listed and their quantities are worked out. Rates for these items are arrived at in the same manner as one do tor ally new item. Price of the additional work is calculated on the basis of these rates. 

ii)  Deleted Work 

Cost of the deleted work will have to be deducted from the approved cost. Items deleted are identified, the quantities which are not be executed are worked out and their cost at the estimated rates is worked out. 

iii)  Alteration 

Estimation of cost of these works comprises two points i) cost of the new item is worked out as in (i) above while the reduction  in the cost due to items replaced  is worked out as in (ii) above. The difference in these two will be the result of the alteration. If (i) is more than (ii) alteration will increase the cost of the work. If (i) is less than (ii) alteration will reduce the cost of the work.