Bill of Quantities: 10 Common Mistakes and How to Avoid Them

The bill of quantities is a crucial tool in the planning and management of construction projects. However, even experienced professionals can stumble upon errors that compromise the accuracy of this vital document. In this article, we'll explore the 10 most common bill of quantities errors and provide practical advice on how to avoid them.

1. Omission of Important Items

The error:

Forgetting to include essential project elements in the estimate.

How to avoid it:

• Use detailed checklists for each phase of the project

• Conduct multiple reviews with different team members

• Implement a cross-check system with project documents

2. Calculation Errors in Measurements

The error:

Incorrect quantity calculations, leading to over or underestimates.

How to avoid it:

• Use specialised software to reduce manual errors

• Apply control formulas to verify calculations

• Do double checks, ideally by a colleague

3. Use of Outdated Prices

The error:

Rely on outdated price lists or fail to consider market fluctuations.

How to avoid it:

• Regularly update pricing databases

• Consult suppliers to obtain updated quotes

• Consider market trends and seasonal factors.

4. Failure to Consider Indirect Costs

The error:

Overlooking costs such as security, waste disposal or general expenses.

How to avoid it:

• Create a section dedicated to indirect costs in the calculation

• Use industry standard percentages to estimate these costs

• Consult experts in safety and environmental management.

5. Vague or Incomplete Descriptions of the Processes

The error:

Provide unclear descriptions that can lead to misunderstandings.

How to avoid it:

• Use precise and standardised technical language

• Include detailed specifications for materials and methodologies

• Attach schematics or technical drawings when necessary.

6. Underestimation of scraps and tolerances

The error:

Not adequately considering material waste and manufacturing tolerances.

How to avoid it:

• Apply realistic scrap rates based on experience

• Consult material data sheets for tolerances

• Include a safety margin for contingencies.

7. Failure to integrate with the timetable

The error:

Do not align the bill of quantities with the project time schedule.

How to avoid it:

• Work closely with the project management team

• Use software that integrates metric calculation and timetable

• Consider costs related to timing (e.g. rentals, labour).

8. Coding and Categorization Errors

The error:

Use inconsistent coding or incorrectly categorize entries.

How to avoid it:

• Adopt a standardized coding system

• Create a clear hierarchical structure for work categories

• Conduct consistency checks on categorization.

9. Neglecting Site Specifics

The error:

Do not consider site-specific conditions that can influence costs.

How to avoid it:

• Carry out careful inspections before completing the calculation

• Consult geologists or other experts for specific assessments

• Include entries for any necessary temporary works.

10. Failure to Update During the Execution of the Works

The error:

Do not update the calculation based on changes that emerge during the works.

How to avoid it:

• Implement a variant management process

• Conduct periodic reviews of the calculation during execution

• Use software that allows real-time updates.

Conclusion

Avoiding these common errors in the bill of quantities requires attention, experience and the use of appropriate tools. Investing time in ongoing training and implementing rigorous control processes can make the difference between a successful project and one plagued by budget overruns and disputes.

Remember: an accurate bill of quantities is not just a document, but a real management tool that guides the success of the project from start to finish.