Methods Of Calculations Of Quantities Of Materials
The calculations of quantities of materials can be done using various methods of estimates. The application of an individual method depends upon the design and shape of the building. The different methods are as under:
- Centre line method.
- Crossing method.
- Out to out and in to in method.
- Bay method.
- Service unit method.
- Centre line method
This method is suitable only if the offsets are symmetrical and the building is more or less rectangular in shape. The centre line of the building is determined carefully after doing deductions for repeated measurements (as explained in the next problem). This centre line acts as length for the complete calculations of the estimate.
If the deduction is not cared for the results of estimates may be wrong. All the walls should have the same section.
- Crossing Method
In this method, lengths and breadths of the masonry walls at plinth level are taken (internal dimension of the room + thickness of the walls) for calculating quantities. The symmetrical offsets are a must as in the case of centerline method.
- Out to out & in to in Method
This method is most practicable under all circumstances and is generally followed in the P.W.D. for computing the quantities of various items. The estimation in this book has been done using this method.
- Bay Method
This method is useful and is generally followed in case of building having several bays. The cost of the one class room is worked out and then multiplied by the number of bays in that building. The extra cost of the end walls and difference in framing. If there is any, should be made, so as to arrive at the correct cost.
- Service Unit Method.
This method is followed in cases such as school building where there are so many class rooms. The cost of one class room us worked out and then multiplied by the number of class rooms to be constrused. In case of Hospitals, the service unit is a bed, in case of Water Tank, it is a litre and in case of Cinema Hall, the service unit is a seat.