Unit 13 �Measurement Techniques �in Construction

Dr Adewale Abimbola, FHEA, GMICE.

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Aim: �Types of quantity take-offs (2)

Objectives: At the end of the lesson, the students should be able to:

Approximate Estimate - RECAP

• Important considerations in SPON’S A&B 2022
• Tender Price Indices (TPI):
• •Tender price indices represent the price for which the contractor offers to do the project for, i.e. cost to client.
• •They consider market considerations such as the availability of labour and materials, and the prevailing economic situation.
• (Page 52)

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Table 1. Tender price indices (AECOM Ltd, 2022)

Approximate Estimate - RECAP

• Important considerations in SPON’S A&B 2022
• Location Factor:
• Prices throughout the book are at a price level index of 132 for Outer London (location factor = 1.00).
• (Page 57)

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Figure 1. Location factor (AECOM Ltd, 2022)

Key terminology:

Gross Internal Floor Area (GIFA or GIA): this is the area of a building measured to the internal face of the perimeter walls at each floor level.

Consult: https://www.designingbuildings.co.uk/wiki/Gross_internal_area_GIA for more information.

Worked Example 1

A new sixth form college

Floor area = 15,000 m²

Cost plan prepared with current TPI = 132

Start on site October 2023, TPI = 130 (pg, 52)

Location: East Midlands = 0.87 (adjustment = -13%)

From Building Prices per Square Metre = £2,075 per m²(pg, 86)

At this stage, the main contractor’s preliminaries, overheads and profit need not be added to the cost of building works as they are included within the Spon’s building prices per square metre rates, but you will need to add on professional fees such as QS, architects, Town and County Planning fees, etc., and other facilitating type costs such as demolition, external works, car parking, bringing services to site, etc.

Worked Example 2

Three storey semi-detached housing

Floor area = 102 m²

Cost plan prepared with current TPI = 132

Start on site March 2023, TPI = 126.7 (pg, 52)

Location: Wales = 0.86 (adjustment = -14%)

From Building Prices per Square Metre = £1,675 per m² (pg, 87)

At this stage, the main contractor’s preliminaries, overheads and profit need not be added to the cost of building works as they are included within the Spon’s building prices per square metre rates, but you will need to add on professional fees such as QS, architects, Town and County Planning fees, etc., and other facilitating type costs such as demolition, external works, car parking, bringing services to site, etc.

Self-assessment Task

a. Using the Building Prices per Square Metre method in Spon’s A&B price book 2022, produce the range (lower and upper) of the total order of cost estimate for a three-storey terrace house in Cardiff, Wales.

Additional information

Total gross internal floor area = 100 m².

Cost plan prepared with current TPI = 132

Start on site May 2023.

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b. Then, compare your estimates to the current price of such similar structure.

What could have caused the variations?.

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Definition - Recap�

• Quantity take-offs are a detailed measurement of materials, labour, and other resources required to complete a construction project.
• Purpose of Quantity take-offs: to create a comprehensive list of all the components and quantities needed for a project, which can then be used for various purposes, including cost estimation, procurement, and project planning.
• They are developed by an estimator/quantity surveyor during the pre-construction phase. They use construction plans, drawings, specifications, and sometimes specialised software to calculate the quantities accurately.

Take-off Quantities - Types

• The two types are:
• Approximate quantities
• Detailed or accurate quantities
• Approximate and detailed quantities are important concepts in the field of quantity surveying. They are important when planning a project.
• In today’s lesson, we will only consider detailed or approximate quantities.

Accurate Quantities

• Accurate or detailed quantities are used for estimating a more precise cost of the project.
• The client would appoint the structural engineers and architects to produce the drawings. The quantity surveyor/estimators can then estimate the price of the project.
• Accurate or detailed quantities are applied for project when you have a detailed or developed drawings, specifications, sections, etc. after the design stage of the project.
• Detailed quantities are found in bill of quantities. [Examine the sample in general section of MS Teams].

Figure 1. Role of measurement in construction process (summary)

Accurate Quantities - Importance

• Production of Bills of Quantities:
• Ensures precise documentation of all materials and work required for the project.
• Forms the basis for fair and accurate tendering by providing a standardised list of project components.
• Tendering and Estimating:
• Accurate quantities are fundamental for contractors to provide competitive and realistic bids during the tendering process.
• Facilitates precise cost estimation, allowing contractors to allocate resources effectively.
• Estimation of a Project’s Value:
• Accurate quantities are integral for determining the overall cost of the project.
• Supports clients, contractors, and stakeholders in understanding the financial scope of the construction endeavour.

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Accurate Quantities - Importance

• Final Account Measurements and Variations:
• Serves as a reference point for measuring the actual work done during construction.
• Enables the assessment of variations and adjustments in the final account based on the actual quantities executed.
• Ordering Materials:
• Accurate quantities are essential for placing accurate orders for construction materials.
• Prevents overordering or shortages, optimising cost-effectiveness and minimising wastage.
• Producing a Quotation for a Work Element:
• Provides a foundation for contractors to generate precise quotations for specific work elements within the project.
• Allows clients to compare quotes accurately and make informed decisions during contractor selection.

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Bibliography

AECOM Ltd (2022) Spon’s Architects’ and Builders’ Price Book. 147th edn. Oxon: Taylor & Francis.

Pearson (2017) BTEC national construction student book. London: Pearson.

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