Here's how the approximate quantities method is used in quantity surveying:
1. Historical Data: Quantity surveyors use historical data from similar construction projects to gather information about the quantities of materials and labour used. This data serves as a starting point for estimating the quantities for the new project.
2. Industry Standards: Industry standards and guidelines provide benchmarks for estimating quantities. For instance, there may be established guidelines for the amount of concrete required per square meter of floor area or the number of bricks needed for a specific type of wall construction.
3. Unit Rates: Quantity surveyors apply unit rates to the estimated quantities to calculate the total cost. Unit rates are the cost of materials or labour per unit, such as the cost per square meter for materials or the cost per hour for labour.
4. Adjustment and Refinement: The initial estimates obtained using the approximate quantities method are adjusted based on project-specific factors. This may involve considering the design, complexity, site conditions, and other relevant factors that could affect the quantities required.
5. Contingency: To account for uncertainties and unexpected variations, quantity surveyors often include a contingency allowance in their estimates. This provides a buffer to cover any additional costs that may arise during the construction process.
6. Reporting: The quantity surveyor presents the estimated quantities and costs in a detailed report. This report serves as a basis for budget planning, procurement, and project management decisions.
7. Revisions and Updates: As the project progresses, quantity surveyors may revise and update their estimates based on actual measurements and changes in the design or construction methods.
The approximate quantities method provides an initial estimate of the quantities required for a construction project. While it may not be as precise as more detailed methods, it offers a cost-effective and time-efficient approach to quantity surveying, especially in the early stages of a project.