Measurement of building works requires precise recording and verification of quantities to ensure accurate billing and cost control. In Quantity Surveying practice in Kenya, the bill measured quantities form the foundation for preparing valuation documents and assessing work progress. This chapter focuses on the preparation of billing sheets or papers, the transfer of booked quantities, and the compilation of price bills of quantities. Mastery of these processes enables Quantity Surveyors to produce reliable interim payment certificates and final accounts compliant with contract requirements.

5.1 Billing paper/sheet

In Kenyan Quantity Surveying practice, the billing paper or sheet is the fundamental document used to record measured quantities for valuation of work done. It serves as the intermediary between the site measurements and the formal bill of quantities or valuation summary. Proper preparation and management of billing sheets ensure transparency, accuracy, and traceability in the measurement and payment process.

5.1.1 Preparation of billing sheet/paper quantities

The preparation of billing sheets involves systematic recording of quantities measured on site, organized by work sections or items. This ensures clarity and ease of reference during valuation and payment stages.

The governing principle is to maintain consistency and accuracy between the billing sheets and the original bill of quantities.

Worked Examples

Example 1: A Quantity Surveyor measures 50 m² of plastering on walls for a hospital project. Prepare the billing sheet entry for this item.

Given: Measured plastering area = 50 m²

Step 1: Identify the item description: Wall plastering

Step 2: Record the quantity measured: 50 m²

Step 3: Confirm unit matches bill of quantities: m²

Answer: Billing sheet entry: Wall plastering, Quantity: 50 m²

Example 2: On a school renovation project, 120 linear meters of timber skirting has been installed. Prepare the billing sheet entry.

Given: Measured timber skirting length = 120 m

Step 1: Item description: Timber skirting

Step 2: Quantity measured: 120 m

Step 3: Unit check: linear meters (m)

Answer: Billing sheet entry: Timber skirting, Quantity: 120 m

Example 3: A hotel construction has completed 30 cubic meters of concrete foundation. Prepare the billing sheet quantity.

Given: Concrete foundation volume = 30 m³

Step 1: Item: Concrete foundation

Step 2: Quantity: 30 m³

Step 3: Unit: cubic meters (m³)

Answer: Billing sheet entry: Concrete foundation, Quantity: 30 m³

Example 4: For a bank building, 200 m² of floor tiles have been laid. Prepare the billing sheet.

Given: Floor tiles area = 200 m²

Step 1: Item: Floor tiles

Step 2: Quantity: 200 m²

Step 3: Unit: square meters (m²)

Answer: Billing sheet entry: Floor tiles, Quantity: 200 m²

Example 5: A SACCO office has installed 15 metal doors. Prepare the billing sheet entry.

Given: Number of metal doors = 15 units

Step 1: Item: Metal doors

Step 2: Quantity: 15 units

Step 3: Unit: number of units

Answer: Billing sheet entry: Metal doors, Quantity: 15 units

5.1.2 Transfer of booked quantities

Transferring booked quantities from measurement records to the billing sheet requires careful verification to avoid duplication or omission. The process involves summarizing measured quantities, cross-checking with measurement books, and preparing the billing sheet for valuation.

The key formula for total billed quantity for each item is:

$$ Q_{billed} = \sum_{i=1}^n Q_{measured,i} $$

where \(Q_{billed}\) is the total billed quantity for the item, and \(Q_{measured,i}\) are individual measured quantities from site records.

Worked Examples

Example 1: A Quantity Surveyor has three measurement records for plastering: 20 m², 35 m², and 25 m². Calculate the total billed quantity.

Given: \(Q_{measured,1} = 20\) m², \(Q_{measured,2} = 35\) m², \(Q_{measured,3} = 25\) m²

$$ Q_{billed} = 20 + 35 + 25 $$$$ Q_{billed} = 80 \text{ m}^2 $$

Answer: Total billed quantity for plastering is 80 m²

Example 2: For timber door frames, three booked quantities are 10 units, 5 units, and 8 units. Calculate total billed quantity.

Given: \(Q_{measured,1} = 10\) units, \(Q_{measured,2} = 5\) units, \(Q_{measured,3} = 8\) units

$$ Q_{billed} = 10 + 5 + 8 $$$$ Q_{billed} = 23 \text{ units} $$

Answer: Total billed quantity for timber door frames is 23 units

Example 3: Measurement records for concrete footing volumes are 5 m³, 7.5 m³, 6 m³, and 8 m³. Calculate total billed quantity.

Given: \(Q_{measured,1} = 5\) m³, \(Q_{measured,2} = 7.5\) m³, \(Q_{measured,3} = 6\) m³, \(Q_{measured,4} = 8\) m³

$$ Q_{billed} = 5 + 7.5 + 6 + 8 $$$$ Q_{billed} = 26.5 \text{ m}^3 $$

Answer: Total billed quantity for concrete footings is 26.5 m³

Example 4: For ceramic wall tiles, booked quantities are 15 m², 20 m², 18 m², and 22 m². Calculate total billed quantity.

Given: \(Q_{measured,1} = 15\) m², \(Q_{measured,2} = 20\) m², \(Q_{measured,3} = 18\) m², \(Q_{measured,4} = 22\) m²

$$ Q_{billed} = 15 + 20 + 18 + 22 $$$$ Q_{billed} = 75 \text{ m}^2 $$

Answer: Total billed quantity for ceramic wall tiles is 75 m²

Example 5: On a university building, four measurement records for electrical conduit length are 100 m, 150 m, 120 m, and 130 m. Calculate total billed quantity.

Given: \(Q_{measured,1} = 100\) m, \(Q_{measured,2} = 150\) m, \(Q_{measured,3} = 120\) m, \(Q_{measured,4} = 130\) m

$$ Q_{billed} = 100 + 150 + 120 + 130 $$$$ Q_{billed} = 500 \text{ m} $$

Answer: Total billed quantity for electrical conduit is 500 m

5.1.3 Price bill of quantities

The price bill of quantities involves applying the contract rates or prices to the billed quantities to determine the value of work done. This is essential for preparing interim payment certificates and final accounts.

The basic formula for value of work done is:

$$ V = Q \times R $$

where \(V\) is the value, \(Q\) is the billed quantity, and \(R\) is the rate or price per unit.

Worked Examples

Example 1: A school project has billed 100 m² of wall plastering priced at Ksh 450 per m². Calculate the value of work done.

Given: \(Q = 100\) m², \(R = 450\) Ksh/m²

$$ V = 100 \times 450 $$$$ V = 45000 \text{ Ksh} $$

Answer: Value of plastering work is Ksh 45,000

Example 2: Timber door frames measured 23 units at Ksh 2,500 per unit. Calculate the value.

Given: \(Q = 23\) units, \(R = 2,500\) Ksh/unit

$$ V = 23 \times 2500 $$$$ V = 57500 \text{ Ksh} $$

Answer: Value of timber door frames is Ksh 57,500

Example 3: Concrete footing volume of 26.5 m³ priced at Ksh 8,000 per m³. Calculate value.

Given: \(Q = 26.5\) m³, \(R = 8,000\) Ksh/m³

$$ V = 26.5 \times 8000 $$$$ V = 212000 \text{ Ksh} $$

Answer: Value of concrete footing is Ksh 212,000

Example 4: Ceramic wall tiles billed quantity 75 m² priced at Ksh 1,200 per m². Calculate value.

Given: \(Q = 75\) m², \(R = 1,200\) Ksh/m²

$$ V = 75 \times 1200 $$$$ V = 90000 \text{ Ksh} $$

Answer: Value of ceramic wall tiles is Ksh 90,000

Example 5: Electrical conduit length 500 m priced at Ksh 350 per meter. Calculate value.

Given: \(Q = 500\) m, \(R = 350\) Ksh/m

$$ V = 500 \times 350 $$$$ V = 175000 \text{ Ksh} $$

Answer: Value of electrical conduit work is Ksh 175,000

Chapter Summary

This chapter focused on the detailed processes involved in the preparation and management of bill measured quantities for building works. It began with the billing paper or sheet, explaining how quantities are accurately prepared and booked, then transferred to ensure consistency and accuracy. The chapter also covered the creation of price bills of quantities, which incorporate unit costs for use in cost estimation and tendering. Attention was given to emerging technologies that are transforming quantity measurement and billing practices. Building Information Modeling was introduced as a powerful tool for integrating design and quantity data. Cloud-based collaboration platforms were shown to enhance communication and data sharing among project stakeholders. The use of artificial intelligence and machine learning was highlighted for automating measurement tasks and improving accuracy. Finally, mobile technology was discussed as a means to facilitate on-site data collection and real-time updates, streamlining the entire billing process.