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Centreline Measurement Convention

Dr Adewale Abimbola, FHEA, GMICE

www.edulibrary.co.uk

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Aim and Objectives

  • Aim: Centreline Measurement Convention

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

• Discuss the significance of calculating centre line in measurement according to NRM2.

• Calculate a mean girth or centre line for a regular and irregular building.

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Introduction

  • • According to NRM2 guidelines, masonry length calculations require measurement along the centreline, regardless of construction type.
  • Some instances, like foundation trench measurements, necessitate calculating the mean girth.
  • Gross building area is measured initially, and deductions, like exterior walls, are made to determine floor space area, always measured on the material's centre line.

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Calculating Girths and Centrelines

The centreline is determined as the midpoint between the external girth and the internal girth.

 

 

 

where, Nr. of corners = Nr. of external corners – Nr. of internal corners

OR

OR

Figure 1. Rectangular-shaped building plan.

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Worked Example 1

  • Calculate the centreline for the regular-shaped building shown.

Figure 2. Rectangular-shaped building plan.

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Solution

Method 1

 

 

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Solution

Method 2

 

 

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Solution

Method 3

 

 

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Worked Example 2

  • Calculate the centreline for the irregular-shaped building shown.

Figure 3. An irregular-shaped building plan.

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Solution

 

 

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Self-assessment Task

  • Calculate the centre lines of the external walls shown in figures 4 – 6.

Figure 4.

Figure 5.

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Self-assessment Task

  • In addition, use AutoCAD to produce the figures and compare your answers with the manual methods.

Figure 6 (The wall is 225 mm thick).

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References /

Bibliography

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  • Designing Buildings Ltd. (2023) Measurement. Available at: https://www.designingbuildings.co.uk/wiki/Measurement (Accessed: 20 November 2023).
  • Lee, S., Trench, W. and Willis, A. (2005) Willis’s elements of quantity surveying. 10th edn. Oxford: Blackwell Publishing.
  • Pearson (2017) BTEC national construction student book. London: Pearson.