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Approximate estimate: what and when

Short answer

An approximate or preliminary estimate is a rough cost prepared before detailed design for feasibility, administrative approval, comparing alternatives and funding. It uses plinth area or unit rates and is usually within 10 to 15% of final cost.

What do you understand by approximate (preliminary) estimate? When and why is it prepared? Also write a short note on it.

Meaning

An approximate (preliminary) estimate is a rough estimate of the probable cost of a project, prepared quickly from the general requirements and past experience, without detailed drawings or item quantities.

When and why it is prepared

  1. At the planning stage, to decide whether the project is feasible and affordable.
  2. To obtain administrative approval and budget allocation from the ministry/municipality.
  3. To compare alternatives (sites, designs, types of structure).
  4. For funding and loan applications, and in the preparation of the annual programme.
  5. When there is no time or data for detailed estimation, as at the start of a design.

Short note

  • Methods: plinth area method, cubic content (cube) rate method, unit base (per bed, per student, per km, per cum of storage) method, approximate quantity method, and the cost of a similar building in the locality.
  • Data: area of the building, the prevailing plinth area rate, percentages for services and contingency.
  • Contents: cost of the civil works (plinth area x rate), special architectural treatment, water supply and sanitary, electrical works, external services, contingency and supervision charge.
  • Accuracy: about 10 to 15% from the final cost; it is not used for tendering.
  • It is followed by the detailed estimate after design is completed.

✓ Answer checked by Claude Opus 5.5 (high effort)

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