After the scope has been analysed and broken down into construction tasks, each task must be quantified prior to pricing. Equal emphasis should be placed on both accurate quantity calculation and accurate pricing. Quantities should be shown in standard units of measure and should be consistent with design units. Assistance for preparing “takeoffs” may be provided by others within the organization in support of cost engineering; however, the responsibility for the accuracy of the quantities remains with the quantity surveyor. Distinction should be made between “net” quantities without waste versus quantities that include waste or loss. This is necessary to ensure duplication does not occur within the estimate.
The detail to which the quantities are prepared for each task is dependent on the level of detail (LOD). Quantity calculations beyond design details are often necessary to determine a reasonable price to complete the overall scope of work for the cost estimate.
A simple example would be fabrication waste material that is a material cost to the project. Project notes will be added at the appropriate level in the estimate to explain the basis for the quantity calculations, to clearly show assumed quantity allowances or quantity contingencies, and to record quantities determined by a quantity surveyor judgment that will be reconciled upon design refinement.
Recommended guidelines in quantity development:
- Coordinate the quantity takeoff process and plan with the estimator.
- Ensure full project scope is reflected within the estimate
- Include a list of materials in quantity takeoffs.
- Utilize a process that easily records the quantity development, i.e., document source and date, estimator name and date, location within the project, demonstrated calculations and additions such as waste or loss.
- Use a systematic approach similar to the construction methodology required.
- Check scales and dimensions on each drawing sheet.
- Highlight or mark drawing areas where quantities have been determined to ensure all scope is captured but not double counted.
- Consider items that have no material but still require cost, e.g., overheads , task setup, training and certifications, and labour preparation.
- Develop quantities within a reasonable range for the work using decimals where critical.
- Add a certain amount of waste, loss, drop off, or length related to the material purchases for a bulk order. Ensure this addition is separate from the original quantity measured.
- Select a natural stopping point during work interruptions.
- Coordinate with designers if the design appears in error, if a better approach is discovered, or a value engineering process is warranted.
- Area (Square meter): Flooring, painting, plastering, Brick walls (12 cm or less),etc.
- Volume (Cubic meter): Brick walls (>12 cm thick), Excavation, Backfilling, Reinforced Concrete, etc.
- Weight (Ton): Metallic works, Reinforcement steel, etc.
- Lump Sum: Some electrical and plumbing works, Manholes, etc.
- Effort (Man-day): Renting of equipment or labour, etc.
It is vitally important that measurement practice applied to buildings is both accurate and consistent. There are a number of situations that require a quantity surveyor to measure and record dimensions from both drawings as well as on site, depending on the stage of the project. In order to standardize measurement rules and conventions, there are a number of standard codes and methods of measurement that are available, depending upon the rule established by the associations.