Understanding Class A, B, C, and D Estimates in Construction According to CIQS
The Canadian Institute of Quantity Surveyors (CIQS) outlines four primary classes of estimates—Class A, B, C, and D. Each class serves a distinct purpose and reflects the level of detail and accuracy needed at different phases of a project's lifecycle.
1. Class D Estimate: The Conceptual Foundation - Early feasibility and budgeting.
Accuracy Range: ±20% to ±30%.
At the conceptual or preliminary stage of a project, the Class D Estimate offers a high-level projection of costs. This estimate relies on broad assumptions, such as cost per square meter, and serves as a foundational tool for determining project viability. It's particularly useful for feasibility studies and initial budgeting discussions, despite its lower accuracy.
2. Class C Estimate: Guiding the Design - Refining the budget during schematic design.
Accuracy Range: ±15% to ±20%.
Once basic design details emerge, the Class C Estimate becomes relevant. It provides costs for major components and quantities, allowing stakeholders to refine the budget and align design choices with financial constraints. This step is crucial for ensuring the project remains financially feasible as the design progresses.
3. Class B Estimate: Design Development Precision - Detailed budgeting with developed designs.
Accuracy Range: ±10% to ±15%.
As the design develops, the Class B Estimate offers a comprehensive breakdown of costs based on more detailed quantities and specifications. This estimate is instrumental in finalizing design decisions and serves as a checkpoint to ensure financial goals are on track before moving to the tendering phase.
4. Class A Estimate: The Final Cost Blueprint - Accurate tendering and project financing.
Accuracy Range: ±5% to ±10%.
The Class A Estimate is prepared at the final stage, using complete project documentation, including drawings, specifications, and bills of quantities. With the highest accuracy, this estimate provides a reliable cost projection for contractor bids and project financing. It ensures precise financial planning and risk management before construction begins.
The Role of CIQS Classifications in Construction
Each class of estimate—D, C, B, and A—marks a progressive journey toward precision and detail. These classifications help manage expectations, inform decision-making, and ensure effective financial planning throughout a project’s lifecycle. By understanding these estimates, stakeholders can align design, budgeting, and execution seamlessly for successful project delivery.
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