The Art of Estimation: A Deep Dive into the Quantity Survey Method

An Insightful Exploration into the Techniques Used by Quantity Surveyors in Construction Cost Estimation

Key Takeaways:

  • Quantity surveying is a critical process in construction project management, with different methods used for estimating costs.
  • The choice of estimation method largely depends on the stage of the project and the available information.
  • Recommended estimation methods include the Unit Method, Superficial Floor Area Method, Elemental Estimate, and Approximate Quantities.
  • The choice of method often progresses as the project advances and more information becomes available.
  • The Cube Method, Storey Enclosure Method, and Superficial Perimeter Method are considered obsolete.
  • Each method has its pros and cons, and the choice depends on the project’s specifics and the Quantity Surveyor’s expertise.

Deciphering Quantity Survey Method: An Introduction

Quantity surveying is a pivotal part of any construction project. The task involves estimating the quantities of materials, time, and labor necessary to complete a project, hence allowing for a comprehensive cost estimation. Various methods are utilized by Quantity Surveyors (QS) to calculate these costs, each with its strengths and weaknesses.

The Methodology: Different Estimation Techniques

The Unit Method

Often employed in the early stages of a project when detailed design plans are not yet available, the Unit Method provides a rough estimate based on the number of ‘personal units’ required by the client. These units could be the number of people who will occupy the building, the number of rooms, desks, keys, parking bays, or any other relevant measurement depending on the project’s nature. The total cost is then calculated by multiplying the number of units by the cost per unit.

The Superficial Floor Area Method

Once sketch designs and floor area details are available, Quantity Surveyors employ the Superficial Floor Area Method. In this technique, the internal gross floor area of the building is multiplied by the construction cost per square meter. The cost per square meter can vary significantly based on region, location, and the type of building, often derived from data provided by local municipalities, property developers, or consulting quantity surveyors.

Elemental Estimate

This method takes a more detailed approach and is employed when drawings with comprehensive information are available. The construction project is broken down into its fundamental building elements, and each element is then priced individually. This technique requires a comprehensive understanding of various aspects of construction, including wall elevations, roof structures, foundation cross-sections, and floor construction, among others. By pricing each element separately and adding these costs, Quantity Surveyors can provide an in-depth and accurate estimate of the project’s total cost.

Approximate Quantities

This advanced method requires detailed drawings and substantial information for building up composite rates. It essentially combines items from a Bill of Quantities into groups that can be quickly measured using the Group unit of measurement, creating a composite rate for each group. Although it takes more time to prepare than other methods, it often yields a more reliable estimate.

A Journey into Obsolete Techniques

Although they are no longer commonly used, methods like The Cube Method, Storey Enclosure Method, and Superficial Perimeter Method have had their time in the spotlight in the quantity surveying field. However, these methods have been largely phased out due to their limited applicability in modern, complex construction projects.

Unwrapping the Science of Quantity Surveying

The success of any construction project hinges heavily on accurate cost estimations, making the role of Quantity Surveyors crucial. Using the Quantity Survey Method – be it the Unit Method, Superficial Floor Area Method, Elemental Estimate, or Approximate Quantities – they provide a roadmap for the project’s financial direction.

It’s worth noting that these techniques are not mutually exclusive but are often applied progressively as the project evolves and more information becomes available. Quantity Surveyors might start with the Unit Method in the early stages, progressing to the Superficial Floor Area Method and Elemental Estimate as more detailed drawings become available, and finally employing the Approximate Quantities technique when sufficient detail is accessible for composite rate calculations.

Conclusion: The Art and Science of Quantity Surveying

In conclusion, quantity surveying is both an art and a science that requires a blend of technical knowledge, practical experience, and professional judgment. While the methods and techniques may vary, the goal remains the same: to ensure the successful completion of construction projects within budget and on schedule. As such, understanding and correctly implementing these techniques are fundamental to the field of quantity surveying.

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