5 Whys
[edit] Introduction
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.
[edit] 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).
Question | Answer | |
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.
A form to help use the 5 Whys quality tool can be downloaded here.
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)
[edit] 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
BSRIA Statutory Compliance Inspection Checklist
BG80/2025 now significantly updated to include requirements related to important changes in legislation.
Shortlist for the 2025 Roofscape Design Awards
Talent and innovation showcase announcement from the trussed rafter industry.
OpenUSD possibilities: Look before you leap
Being ready for the OpenUSD solutions set to transform architecture and design.
Global Asbestos Awareness Week 2025
Highlighting the continuing threat to trades persons.
Retrofit of Buildings, a CIOB Technical Publication
Now available in Arabic and Chinese aswell as English.
The context, schemes, standards, roles and relevance of the Building Safety Act.
Retrofit 25 – What's Stopping Us?
Exhibition Opens at The Building Centre.
Types of work to existing buildings
A simple circular economy wiki breakdown with further links.
A threat to the creativity that makes London special.
How can digital twins boost profitability within construction?
The smart construction dashboard, as-built data and site changes forming an accurate digital twin.
Unlocking surplus public defence land and more to speed up the delivery of housing.
The Planning and Infrastructure Bill
An outline of the bill with a mix of reactions on potential impacts from IHBC, CIEEM, CIC, ACE and EIC.
Farnborough College Unveils its Half-house for Sustainable Construction Training.
Spring Statement 2025 with reactions from industry
Confirming previously announced funding, and welfare changes amid adjusted growth forecast.
Scottish Government responds to Grenfell report
As fund for unsafe cladding assessments is launched.
CLC and BSR process map for HRB approvals
One of the initial outputs of their weekly BSR meetings.
Building Safety Levy technical consultation response
Details of the planned levy now due in 2026.
Great British Energy install solar on school and NHS sites
200 schools and 200 NHS sites to get solar systems, as first project of the newly formed government initiative.
600 million for 60,000 more skilled construction workers
Announced by Treasury ahead of the Spring Statement.