Abstracting measured quantities is a critical step in the Quantity Surveying process, enabling the efficient compilation of detailed measurements into manageable summaries. This chapter focuses on the preparation and use of abstracting sheets, essential for organizing measurements before pricing and valuation. It also covers the technique of running through dimensions, a method used to verify and cross-check measurements for accuracy and consistency in building works.

4.5 Abstracting sheet Practical/Projects

4.5.1 Preparation of abstracting sheet

Concept and formula

The abstracting sheet records quantities measured from drawings or site measurements and groups them logically. There is no mathematical formula but a standardized format is followed.

Worked Examples

Example 1: Preparing an abstracting sheet for wall plastering quantities

Given: Wall plaster area measured as 120 m², window openings 4 m² to be deducted

• Total plaster area = Wall area, openings
• \( 120 - 4 = 116 \, m^2 \)

Abstracting sheet entry: Plastering area = 116 m²

Example 2: Abstracting concrete volume for a beam

Given: Beam dimensions, length 6 m, width 0.3 m, depth 0.5 m

• Volume \( V = L \times W \times D \)
• \( V = 6 \times 0.3 \times 0.5 = 0.9 \, m^3 \)

Abstracting sheet entry: Concrete volume = 0.9 m³

Example 3: Abstracting quantities for floor finishes

Given: Floor area 80 m², 10% wastage allowance

• Net quantity = Floor area × (1 + wastage)
• \( 80 \times 1.10 = 88 \, m^2 \)

Abstracting sheet entry: Floor finish = 88 m²

Kenyan Context Note:

In practice, abstracting sheets are commonly used by Kenyan construction firms such as Epco Builders Ltd and government agencies like the State Department for Public Works. For example, when preparing an abstracting sheet for a project at Kenyatta National Hospital, the measured quantities would be grouped and summarized in the same way as shown above.

4.5.2 Transfer of booked quantities

Transferring booked quantities from measurement books to abstracting sheets requires accuracy and verification to prevent discrepancies in costing.

Concept and formula

The transfer process is a systematic transcription of quantities without change, but cross-checking totals is essential.

Worked Examples

Example 1: Transferring wall blockwork quantity

Given: Blockwork measured as 50 m² in measurement book

• Transfer quantity = 50 m²

Abstracting sheet entry: Blockwork = 50 m²

Example 2: Transferring excavation volume

Given: Excavation volume measured as 12 m³

• Transfer quantity = 12 m³

Abstracting sheet entry: Excavation = 12 m³

Example 3: Transferring steel reinforcement weight

Given: Reinforcement measured as 150 kg

• Transfer quantity = 150 kg

Abstracting sheet entry: Steel reinforcement = 150 kg

Kenyan Context Note:

For instance, in projects managed by the National Construction Authority (NCA), transferring booked quantities from site measurement books to abstracting sheets is a standard procedure to ensure accuracy in the Bills of Quantities for public infrastructure works such as roads and schools.

Chapter Summary

This chapter covers the process of abstracting measured quantities in building works, starting with the preparation of the abstracting sheet, which organizes all relevant data systematically for clarity and accuracy. It explains how to transfer booked quantities onto the abstracting sheet to ensure consistency between measurement and costing. The chapter then discusses running through dimensions, detailing the symbols commonly used to represent various measurements and ensure precise communication. Following that, it addresses the casting up of dimensions, including the specific symbols applied during this stage to consolidate measurements effectively. Finally, the chapter explains the calculation of net quantities by accurately summing and adjusting the measured data to reflect the true quantities required for construction. Together, these topics provide a comprehensive guide for managing and interpreting measurement data in building projects.