Timber Shoring Safety
The Problem
Excavation work is one of the most dangerous tasks on any construction site, with trench cave-ins being a leading cause of serious injuries and fatalities. While less common today due to modern systems, timber shoring still plays a vital role—especially in complex trenches with multiple services. If timber shoring is not installed or maintained properly, it can fail without warning, trapping workers and leading to life-threatening consequences. Today, we’ll focus on the hazards of timber shoring and how to keep ourselves safe while working under its protection.
Identify the Hazards
- Improper Installation: Timber shoring that isn’t installed under the supervision of a Competent Person increases the risk of failure.
- Component Damage: Broken or split timbers, bent screw-jack pipes, or loose cross braces can compromise structural integrity.
- Unstable Soil: Shifting ground around timber shoring may lead to collapse.
- Unsafe Entry/Exit: Climbing on braces or using unapproved access methods increases fall risk and injury.
Safety Practices and Preventative Measures
Competent Person Approval
- Timber shoring must be installed and signed off by a Competent Person.
- Use only WorkSafe-approved systems, or follow an engineered design when required.
Safe Entry and Exit
- Use secured ladders or designated access points only.
- Ladders must extend at least one metre above the trench edge for safe use.
- Never climb on cross braces or screw jacks—they are not designed for access.
Hazard Awareness
- Avoid Unprotected Areas: Only work within the shored section of the trench. Unshored areas can cave in at any moment.
- Inspect for Damage: Look for cracked timbers, shifting braces, or signs of ground movement. Report issues immediately.
Inspection and Maintenance
- Make sure all components—such as pipe screw jacks and braces—are in place and secure.
- Excavation below the bottom of the timber shoring must be inspected and cleared by a Competent Person.
Stability During Excavation
- Ensure uprights are snug against the trench wall to prevent gaps or shifting.
- Any movement, such as dislodged braces or sliding uprights, must be reported and addressed before continuing work.
Real-Life Case or Scenario
Last year, a worker entered a trench where timber braces had come loose due to soft, shifting soil. The trench had not been inspected before re-entry. A partial collapse occurred, burying the worker up to his waist. Quick action by co-workers prevented more serious injury. This incident could have been avoided with a proper inspection and sign-off by the Competent Person.
Employee Responsibilities
- Never enter a trench with timber shoring unless cleared by a Competent Person.
- Use proper access (e.g., ladders)—never climb on braces.
- Report any signs of damage or movement in the shoring system.
- Stay within protected (shored) areas at all times—never walk into unprotected sections.
Employer Responsibilities
- Ensure timber shoring is designed, installed, and maintained in line with WorkSafe NZ guidelines or an engineered plan.
- Appoint a Competent Person to supervise and inspect all trenching work.
- Immediately replace or repair damaged shoring components.
- Provide training and instruction to workers on the safe use of timber shoring.
Discussion & Questions
- “What do you look for when inspecting timber shoring before entering a trench?”
- “Have you seen trench stability issues or problems with timber shoring?”
- “What’s the best way to stay in touch with the Competent Person during trench work?”
Encourage team members to share ideas, experiences, and any questions about the proces
Commitment/Action Plan
Let’s commit to inspecting all timber shoring before entering a trench and ensuring safe entry and exit procedures are followed. Starting today, no one enters a trench without Competent Person approval. If you spot unstable soil, broken timber, or shifting supports—report it immediately.
Wrap-Up
Timber shoring, when used correctly, offers vital protection against trench collapse. But it must be installed properly, inspected regularly, and used safely. By working closely with the Competent Person and following best practices, we can protect ourselves and our co-workers. Thanks for your commitment to safety.
Standards Overview
Under the Health and Safety at Work Act 2015 (HSWA) and WorkSafe NZ excavation safety guidelines, employers and PCBUs must:
- Use protective systems (such as timber shoring) in trenches deeper than 1.5 metres, unless the excavation is cut back to a safe slope.
- Ensure trench work is supervised and inspected by a Competent Person.
- Follow either timber shoring charts or an engineered design when timber systems are used.
- Excavation up to 600 mm below the bottom of timber shores may be allowed, but only under strict supervision and inspection.
Refer to WorkSafe NZ’s Excavation Safety Good Practice Guidelines for detailed requirements.
Disclaimer
These toolbox talks are provided for informational and educational purposes only and are not a substitute for professional legal, health and safety, or regulatory advice.
The content reflects recognised best practices and general industry standards as at the date of publication. However, it may not be applicable to all workplace environments or specific operational contexts.
It is the responsibility of the Person Conducting a Business or Undertaking (PCBU), as well as officers, workers, and other duty holders under the Health and Safety at Work Act 2015 (HSWA), to ensure compliance with all relevant laws, regulations, and WorkSafe New Zealand guidance.
The authors, presenters, and distributors of this toolbox talk disclaim all liability for any loss, damage, or injury arising from the use or reliance on the information provided. Users should seek advice from a suitably qualified health and safety professional or legal advisor for guidance tailored to their specific circumstances.
Always follow your organisation’s policies, procedures, and safe work practices to manage risks and maintain a safe and healthy workplace.
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