- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 19 Sep 2019
The ‘root cause’ is the true or underlying reason why something has happened - usually something that has gone wrong. Finding the root cause enables appropriate action to be taken to prevent a problem from happening again - for example, when a nonconformity report (NCR) is raised. Otherwise, action taken may be focussed on the effect rather than the true cause. Therefore, when undertaking investigations into an incident (whether quality or otherwise), specific attention is given to identifying the root cause.
The ‘5 Whys’ is a very simple but effective way to help determine the root cause of an issue by continually asking ‘why’ until the root cause is identified.
 What is 5 Why’s?
It is not unusual for young children to ask ‘why’ when discussing something. Having been given an answer by the adult, the young child then asks ‘why’ again but this time in relation to the answer given, the adult answers and the child persists asking why again in relation to the next answer and so on. This can be very annoying! However, the child is actually demonstrating the principles of the ‘5 Whys’ very effectively. The child (perhaps unknowingly) is trying to find the basis of the reason for the adult’s decision.
The ‘5 whys’ quality tool is simply a way to delve deeper and deeper into the reasons for what has happened. Each time a question is asked and answered we can refer to this as a ‘level’. When no further answers can be given, theoretically, the ‘root cause’ has been determined.
It is often assumed that asking ‘why’ 5 times allows the root cause to be identified (although this may not always be the case).
|Level 1||Why was the bolt not tightened to the correct torque?||The operative was not aware that the bolt had to be tightened to a specified torque.|
|Level 2||Why was the operative not aware that the bolt had to be tightened?||The operative did not receive information from the supervisor.|
|Level 3||Why did the supervisor not supply information to the operative?||The supervisor did not have the information available.|
|Level 4||Why did the supervisor not have the information available?||The supervisor could not access the network drive system.|
|Level 5 (root cause)||Why could the supervisor not access the network drive system?||There was no power due to electrical testing.|
It is important to recognise that an issue may initially appear to be the result of one thing when actually the root cause is very different. It is the root cause that will enable the problem to be solved and prevent it from happening again.
Original article written by Mike Buss, reviewed by Tony Hoyle on behalf of the CQI Construction Special Interest Group, and accepted for publication by the Competency Working Group on 7 March 2018.
--ConSIG CWG 13:32, 28 Feb 2019 (BST)
 Related articles on Designing Buildings Wiki
- Annex SL
- Change control: a quality perspective
- Compensation event.
- Delay to completion.
- Delay to progress.
- Digital quality management in construction.
- Dispute resolution.
- Disruption claims in construction.
- How to write an inspection and test plan.
- Inspection and test plan.
- International research into the causes of delays on construction projects.
- Lifts and escalators: a quality perspective.
- Mobilisation to site: a quality perspective.
- Relevant event.
- Relevant matter.
- Structural steelwork: a quality perspective.
- Why should quality be important to the construction industry?
Featured articles and news
What future infrastructure provision might look like.
Highlighting the health benefits of home improvement.
Pavilions for music, entertainment, and leisure. Book review.
Broadening our understanding of Dublin’s chequered social history.
The charm of London's Cabmen's shelters.
Future Weather Files research tool looking for feedback.
Exploring the Colour Rendering Index.
Why it's important to find out what went wrong.
ECA reviews the shape of the construction job market.
Why proper room acoustics make a difference.
Initiative puts gas networks on the path to net zero.
WICE Woman Architectural Technologist of the Year 2019.
Traditional low-energy approaches to comfort.
Revisiting the McArthurGlen Designer Outlet in Ashford.
USA In-Use Version 6 is now available.
The rise of architectural barbarism.
In contentious political contexts heritage can be more fractious.