Types of Rough cost estimate
Rough cost estimates are of the following types.
- Preliminary/approximate/rough cost estimate
- plinth area estimate
- cube rate estimate
- approximate quantity method estimate
Preliminary/approximate/rough cost estimate
Estimate of cost before the construction, from the line planes of architectural drawings when detail and structural drawings are not prepared.
Objective of rough cost estimate
These estimates are used for obtaining administrative approval from the concerning authority.
Average unit cost is worked out for projects of similar nature like the project under consideration. In this method average unit cost is multiplied by total quantity of present work in the same unit.
Average unit cost like:
- building cost per person
- hospital cost per bed
- student hostel cost per student
- hostels cost per person
Plinth area method
Covered area by building is worked out and unit obtained is square feet. For cost per square feet of the covered area, plinth area method is usually used. This method is practical and usual method of obtaining rough cost estimate.
Cube rate estimate
In cube rate estimate, third dimension height is also considered. Height is multiplied with the covered area. Cube rate is established in this method.
The covered area is first calculated and then multiplied with the ceiling height. For each floor level, different cube rate estimate is obtained.
Approximate quantity method estimate
In this method, a linear length is used for estimation. Therefore, the total length of the object is calculated in running foot. This length is then multiplied with the running cost per running foot of the object to get the cost of the wall.
In this method, the structure is divided into sub-structure and super structure. This method is used in roads, railways, bridges, streets etc.
By using this method, cost may be found in following ways.
- For roads and railways, cost/km or cost/miles
- for streets, cost per 100 feet or cost per 30 meters
- for bridges, cost per foot or cost per meter of the clear span. Clear span is the clear distance between the supports of the bridges.