Abstracting measured quantities is a core skill for quantity surveyors tasked with preparing accurate cost estimates and bills of quantities. This chapter focuses on the processes involved in organizing and summarizing measured building work data into abstracting sheets, which form the basis for cost analysis and tender documentation. It also covers the technique of running through dimensions, a systematic method used to verify and record measurements with standardized symbols. Mastery of these techniques ensures precision and efficiency in quantity surveying practice in Kenya’s construction industry.

4.1 Abstracting sheet Practical/Projects

Abstracting sheets are essential documents where detailed measurements are compiled and summarized for pricing and costing. In the Kenyan quantity surveying profession, abstracting sheets enable clear communication of quantities for procurement and contract management. This section covers the preparation of abstracting sheets and the transfer of booked quantities from measurement records.

4.1.1 Preparation of abstracting sheet

The preparation of an abstracting sheet involves organizing measured quantities into a structured format that facilitates pricing and analysis. The abstract sheet typically lists item descriptions, units, quantities, and references to original measurements.

The governing principle is:

$$ \text{Abstracted Quantity} = \sum \text{Booked Quantities from Measurement Sheets} $$

Worked Examples

Example 1: A quantity surveyor has measured 5 slabs each with an area of 12 m². Prepare the abstracted quantity.

Given: Number of slabs = 5, Area per slab = 12 m²

$$ \text{Abstracted Quantity} = 5 \times 12 $$

$$ = 60 \text{ m}^2 $$

Answer: 60 m²

Example 2: A column has been measured with four sides each 0.3 m wide and 3 m high. The quantity to be abstracted is length of shuttering required.

Given: Number of sides = 4, Width per side = 0.3 m, Height = 3 m

$$ \text{Perimeter} = 4 \times 0.3 = 1.2 \text{ m} $$

$$ \text{Shuttering area} = \text{Perimeter} \times \text{Height} = 1.2 \times 3 $$

$$ = 3.6 \text{ m}^2 $$

Answer: 3.6 m²

Example 3: A beam of length 8 m, cross-sectional width 0.4 m, and depth 0.6 m is measured. Abstract the volume of concrete.

Given: Length = 8 m, Width = 0.4 m, Depth = 0.6 m

$$ \text{Volume} = \text{Length} \times \text{Width} \times \text{Depth} $$

$$ = 8 \times 0.4 \times 0.6 $$

$$ = 1.92 \text{ m}^3 $$

Answer: 1.92 m³

Example 4: Five identical walls each 4 m long, 3 m high, and 0.2 m thick are measured. Abstract the total wall volume.

Given: Number of walls = 5, Length = 4 m, Height = 3 m, Thickness = 0.2 m

$$ \text{Volume per wall} = 4 \times 3 \times 0.2 = 2.4 \text{ m}^3 $$

$$ \text{Total volume} = 5 \times 2.4 = 12 \text{ m}^3 $$

Answer: 12 m³

Example 5: A slab with dimensions 10 m by 6 m and thickness 0.15 m is measured. Abstract the quantity of concrete.

Given: Length = 10 m, Width = 6 m, Thickness = 0.15 m

$$ \text{Volume} = 10 \times 6 \times 0.15 $$

$$ = 9 \text{ m}^3 $$

Answer: 9 m³

Additional Worked Example

Example 6: A measurement sheet records three different areas for suspended slabs: 10 m², 15 m², and 8 m². Abstract the total quantity.

Given: Areas = 10 m², 15 m², 8 m²

$$ \text{Abstracted Quantity} = 10 + 15 + 8 $$

$$ = 33\ \text{m}^2 $$

Answer: 33 m²

4.1.2 Transfer of booked quantities

Transferring booked quantities involves moving measurements from field books or measurement sheets into the abstracting sheet accurately to avoid errors in costing.

The principle formula is:

$$ \text{Abstracted Quantity} = \sum \text{Booked Quantities Transferred} $$

Worked Examples

Example 1: Measurement sheet shows 20 m² of plastering done on walls. Transfer this quantity to the abstracting sheet.

Given: Plastered area = 20 m²

$$ \text{Abstracted Quantity} = 20 \text{ m}^2 $$

Answer: 20 m²

Example 2: Booked quantity for floor screeding is 15 m². Confirm the total abstracted quantity after transferring.

Given: Booked quantity = 15 m²

$$ \text{Abstracted Quantity} = 15 \text{ m}^2 $$

Answer: 15 m²

Example 3: A measurement book shows 30 m length of pipework installed. Transfer this quantity.

Given: Pipe length = 30 m

$$ \text{Abstracted Quantity} = 30 \text{ m} $$

Answer: 30 m

Example 4: Booked quantity of blockwork is 50 m². Transfer to the abstract sheet.

Given: Blockwork area = 50 m²

$$ \text{Abstracted Quantity} = 50 \text{ m}^2 $$

Answer: 50 m²

Example 5: Booked quantity for excavation is 12 m³. Transfer to abstracting sheet.

Given: Excavation volume = 12 m³

$$ \text{Abstracted Quantity} = 12 \text{ m}^3 $$

Answer: 12 m³

Additional Worked Example

Example 6: Measurement sheets show three booked quantities for blockwork: 12 m², 18 m², and 20 m². Transfer and sum these to the abstracting sheet.

Given: Blockwork areas = 12 m², 18 m², 20 m²

$$ \text{Abstracted Quantity} = 12 + 18 + 20 $$

$$ = 50\ \text{m}^2 $$

Answer: 50 m²

Chapter Summary

This chapter focuses on the process of abstracting measured quantities in building works, starting with the preparation of the abstracting sheet, which organizes and summarizes the quantities derived from measurements. It explains how to transfer booked quantities accurately onto the abstracting sheet to ensure clarity and correctness in the documentation. The chapter then covers running through dimensions, detailing the common symbols used to represent various measurements and how they assist in the clear communication of dimensional data. Following this, casting up dimensions is discussed, including the symbols used to compile and sum these dimensions effectively. Finally, the chapter addresses the calculation of net quantities, emphasizing the importance of precise arithmetic to determine the actual amounts of materials or work needed. Together, these topics provide a comprehensive overview of managing and interpreting measurements for building projects.