Among common estimating methods (preliminary, plinth-area, cube-rate, detailed), which provides the most reliable and accurate cost estimate for a project?

Introduction / Context:
Estimating accuracy improves as the level of project definition increases. Early-stage estimates rely on proxies (area, volume), while a detailed estimate is built from measured quantities and current rates, yielding the highest reliability for budgeting and tendering.

Given Data / Assumptions:

• Project drawings, specifications, and schedules are available to different degrees.
• We compare four methods: preliminary, plinth-area, cube-rate, and detailed.
• We seek the most reliable among them.

Concept / Approach:
Preliminary and plinth-area estimates are suitable for feasibility and rough budgeting. Cube-rate estimates incorporate storey height (volume) but still generalize. A detailed estimate itemizes quantities (BOQ), applies unit rates, includes allowances for wastage, overheads, and contingencies, and is thus the most accurate and reliable.

Step-by-Step Solution:
Recognize data depth: Detailed > Cube-rate > Plinth-area > Preliminary.Reliability follows data granularity and specificity.Therefore, Detailed estimate is the most reliable.

Verification / Alternative check:
Award-of-contract processes require detailed estimates and BOQs; early-stage screening does not.

Why Other Options Are Wrong:

• Preliminary/Plinth/Cube-rate: Useful but less precise due to assumptions and averages.
• None of these: Incorrect because “Detailed estimate” is a valid and correct option.

Common Pitfalls:
Relying on early-stage estimates for final budgeting; ignoring market rate updates and location factors in a detailed estimate.

Final Answer:
Detailed estimate