Civil Engineering


Various types of estimates as prepared are of following types:-

1. Approximate or Preliminary Estimate

The estimate is prepared to know the approximate cost of the work and to take the administrative approval by the competent authority of the department for which the work is to be executed this estimate is also called as ROUGH COST ESTIMATE. The cost of building, cost of land, cost of roads etc. are shown separately in this estimate. The necessity and urgency of the estimate and rates arrived at for knowing the cost are fully explained in this estimate. The specifications to be adopted are also fully explained. The rates provided in the estimate and for unit basis i.e., per sq.m for buildings, per km length of road or canal and per running meter of span for culverts and bridges. These rates are derived from the similar type of structure already constructed in the near vicinity of the work.

2. Plinth Area Estimate

The estimate prepared on the plinth area basis of the building by using suitable plinth area rates is called the plinth area estimate. The area of the building at the plinth level, by taking the external dimensions is worked out and is multiplied by suitable rate per sq m. The cost thus arrived at is the cost of building based on plinth area. The plinth area rates for different types of buildings are different i.e., the rates for residential buildings are less than the rates for the hospital buildings etc. Plinth area estimate is also a rough cost estimate.

3. Cubical Content Estimate

This estimate is also an approximate and is prepared on the basis of cubical contents of the building. The cost of the building is calculated by multiplying the plinth area by the height of building and cubical content rate i.e., plinth area multiplied by; height multiplied by; cubical content rate. The plinth area is calculated as staved above and the height is taken from the top of flat roof (or halfway of the sloped roof) to the top of concrete in foundation. The cubical content rate is deduced from the cost of similar building in the locality. The parapet is not taken in the calculations. This estimate is more accurate than the plinth area estimate.

4. Detailed Estimate

After obtaining the administrative approval of the concerned department against the rough cost estimate, the detailed estimate is prepared by P.W.D. department. As this estimate is based on the plans and sections of the building so it is the most accurate estimate. The quantities of items under various sub heads of work are calculated from the drawings and cost of each item is worked out separately according to the prevalent market rates and is totaled.  After doing the total of all items a percentage of 3 to 5 is added for unforeseen items, change of design and provision of petty-establishment. Grand total so obtained gives the estimated cost of building. This estimate is then submitted to the competent authority for according technical sanction. The competent authority may be Chief Engineer or Superintending Engineer of the P.W.D. department. Th detailed estimate is accompanied by report, design and scope, detailed drawings, detailed specifications, justification of the rates provided and the limit for execution of the work. The work us executed according to the detailed estimate.

5. Revised Estimate

When the cost of the estimate exceeds or likely to increase by 10% or more, a revised estimate is required to be prepared. It is accompanied by the comparative statement showing the variations of each item of work and giving the reasons of excess. The excess may be due to change of design and scope of variation in rates etc.

6. Supplementary Estimate

When some addition to the original work is made a fresh detailed estimate for the additional work is prepared to supplement the original estimate and thus called supplementary estimate. This estimate is in addition to the original estimate.

7. Annual Repair of Annual Maintenance Estimate

This estimate is prepared to carry out annual repairs or maintenance. The amount of annual repair estimate should not exceed more than 1 1/2% of the capital cost of the building. Annual repair are much common in road work for which annual repair estimates are prepared to carry out the work.

8. Extension and Improvement Estimate

When some changes and extensions are required to be made in the old work, the cost of which cannot be met by the annual repair/maintenance estimate, a detailed estimate is prepared for such work which is called as Extension and Improvement estimate.