Quantity Survey professionals in Kenya rely heavily on accurate measurement and systematic recording of civil works to ensure precise costing and project control. Abstracting measured quantities is a critical step that involves summarizing detailed measurements into concise, organized sheets for valuation and tendering purposes. This chapter focuses on the preparation and use of abstracting sheets and the process of running through dimensions, both essential skills for effective quantity surveying in civil engineering projects.

4.1 Abstracting sheet

4.1.1 Preparation of abstracting sheet

The preparation of an abstracting sheet involves systematically organizing measured items into a clear, concise format that facilitates easy calculation and verification. The abstracting sheet acts as a bridge between detailed field measurements and the final bill of quantities, ensuring that quantities are neither duplicated nor omitted.

The general formula for total quantity calculation on an abstracting sheet is:

$$ Q_{total} = \sum_{i=1}^n Q_i $$

where \(Q_i\) represents individual measured quantities for each item.

Worked Examples

Example 1: A quantity surveyor measures the length of a retaining wall as 30 m, with a consistent thickness of 0.3 m and height of 2.5 m. Calculate the total volume to be abstracted onto the sheet.

Given:
Length \(L = 30\, m\), Thickness \(T = 0.3\, m\), Height \(H = 2.5\, m\)

$$ Q = L \times T \times H $$

$$ Q = 30 \times 0.3 \times 2.5 $$

$$ Q = 22.5\, m^3 $$

Answer: 22.5 m³

Example 2: A slab has been measured as 15 m by 10 m with a thickness of 0.15 m. Determine the quantity to record on the abstracting sheet.

Given:
Length \(L = 15\, m\), Width \(W = 10\, m\), Thickness \(T = 0.15\, m\)

$$ Q = L \times W \times T $$

$$ Q = 15 \times 10 \times 0.15 $$

$$ Q = 22.5\, m^3 $$

Answer: 22.5 m³

Example 3: A trench for foundation footing is measured as 50 m long, 0.6 m wide, and 1.2 m deep. Calculate the abstracted quantity.

Given:
Length \(L = 50\, m\), Width \(W = 0.6\, m\), Depth \(D = 1.2\, m\)

$$ Q = L \times W \times D $$

$$ Q = 50 \times 0.6 \times 1.2 $$

$$ Q = 36\, m^3 $$

Answer: 36 m³

Example 4: A column has a square cross-section measuring 0.4 m by 0.4 m and a height of 3 m. Determine the quantity to abstract.

Given:
Cross-section \(0.4\, m \times 0.4\, m\), Height \(H = 3\, m\)

$$ Q = 0.4 \times 0.4 \times 3 $$

$$ Q = 0.16 \times 3 $$

$$ Q = 0.48\, m^3 $$

Answer: 0.48 m³

Example 5: A concrete beam is 6 m long with a rectangular cross-section 0.3 m wide and 0.5 m deep. Calculate the quantity for abstraction.

Given:
Length \(L = 6\, m\), Width \(W = 0.3\, m\), Depth \(D = 0.5\, m\)

$$ Q = L \times W \times D $$

$$ Q = 6 \times 0.3 \times 0.5 $$

$$ Q = 0.9\, m^3 $$

Answer: 0.9 m³

Example 6: A slab for the main entrance of the Nairobi City County Hall is measured as 20 m by 12 m with a thickness of 0.2 m. Calculate the quantity to record on the abstracting sheet.

Given:
Length \(L = 20\, m\), Width \(W = 12\, m\), Thickness \(T = 0.2\, m\)

$$ Q = L \times W \times T $$

$$ Q = 20 \times 12 \times 0.2 $$

$$ Q = 48\, m^3 $$

Answer: 48 m³

Example 7: A column for the Kenya Revenue Authority headquarters has a rectangular cross-section measuring 0.5 m by 0.3 m and a height of 4 m. Determine the quantity to abstract.

Given:
Cross-section \(0.5\, m \times 0.3\, m\), Height \(H = 4\, m\)

$$ Q = 0.5 \times 0.3 \times 4 $$

$$ Q = 0.15 \times 4 $$

$$ Q = 0.6\, m^3 $$

Answer: 0.6 m³

4.1.2 Transfer of booked quantities

Transferring booked quantities from measurement books to the abstracting sheet requires accuracy and consistency to avoid errors in project costing. The process involves consolidating individual measurements into summary quantities, ensuring each item is correctly identified and recorded.

The total abstracted quantity for an item is:

$$ Q_{abstracted} = \sum_{j=1}^m Q_{booked_j} $$

where \(Q_{booked_j}\) are individual booked quantities.

Worked Examples

Example 1: A measurement book contains three entries for excavation: 5 m³, 7 m³, and 8 m³. Calculate the total quantity to transfer to the abstracting sheet.

Given:
\(Q_1=5\, m^3\), \(Q_2=7\, m^3\), \(Q_3=8\, m^3\)

$$ Q_{abstracted} = 5 + 7 + 8 $$

$$ Q_{abstracted} = 20\, m^3 $$

Answer: 20 m³

Example 2: Concrete measurements for a slab are recorded as 10.5 m³, 12.3 m³, and 9.7 m³. Determine the total quantity to transfer.

Given:
\(Q_1=10.5\, m^3\), \(Q_2=12.3\, m^3\), \(Q_3=9.7\, m^3\)

$$ Q_{abstracted} = 10.5 + 12.3 + 9.7 $$

$$ Q_{abstracted} = 32.5\, m^3 $$

Answer: 32.5 m³

Example 3: Steel reinforcement bar quantities booked are 150 kg, 200 kg, and 180 kg. Find the total quantity to transfer.

Given:
\(Q_1=150\, kg\), \(Q_2=200\, kg\), \(Q_3=180\, kg\)

$$ Q_{abstracted} = 150 + 200 + 180 $$

$$ Q_{abstracted} = 530\, kg $$

Answer: 530 kg

Example 4: Measurements for wall plastering are 25 m², 30 m², and 28 m². Calculate the abstracted quantity.

Given:
\(Q_1=25\, m^2\), \(Q_2=30\, m^2\), \(Q_3=28\, m^2\)

$$ Q_{abstracted} = 25 + 30 + 28 $$

$$ Q_{abstracted} = 83\, m^2 $$

Answer: 83 m²

Example 5: Measurements for formwork are recorded as 40 m², 35 m², 45 m², and 30 m². Determine the total quantity.

Given:
\(Q_1=40\, m^2\), \(Q_2=35\, m^2\), \(Q_3=45\, m^2\), \(Q_4=30\, m^2\)

$$ Q_{abstracted} = 40 + 35 + 45 + 30 $$

$$ Q_{abstracted} = 150\, m^2 $$

Answer: 150 m²

Chapter Summary

This chapter focused on the process of abstracting measured quantities in civil works. It began with the preparation of the abstracting sheet, detailing how to organize and set up the sheet for efficient recording of measurements. The transfer of booked quantities to the abstracting sheet was explained to ensure accuracy and consistency. The chapter then covered running through dimensions, introducing the standard symbols used for this step to facilitate clear communication of measurements. Next, casting up dimensions was discussed, including the specific symbols employed to summarize and verify the measurements taken. Finally, the calculation of net quantities was explored, demonstrating how to derive the final values needed for billing or further analysis. Throughout, emphasis was placed on precision and correct notation to maintain the integrity of the measurement process.