ISSN: 1195-5228

Issued: June 22, 2015

The purpose of this alert is to provide important information regarding mast-climbing work platform safety. The recent death of two Ontario workers who were on a mast-climbing work platform (MCWP) when it collapsed prompted Ministry of Labour, Training and Skills Development Inspectors and Engineers to undertake a review of similar mast-climbing platforms. Any serious defects in the structural elements of mast-climbing work platforms could, if not addressed, significantly increase the likelihood of failure.

Suppliers and employers, including those who own, use, or allow such equipment to be used at a workplace or project are advised of the significant potential for these structures to collapse if they are not properly inspected and maintained in accordance with good engineering practice and manufacturer’s instructions.

Hazard summary

Welds in the structural components of the work platform may have cracks, and in some cases may be missing. Weld defects may not be detectible by visual examination and non-destructive testing may be required to determine if cracks in welds are present. Critical welds may not be readily accessible for inspection and non-destructive testing without partially removing the deck and partially dismantling the platform.

Any structural deficiencies identified during an inspection of a mast-climbing work platform in load carrying members, including mast sections, platform sections and ties, will require the platform to be taken out of service immediately.

Corrective action to address structural deficiencies must be taken before the equipment is placed back in service.


MCWPs have become a common type of access equipment in the construction industry primarily in the restoration, masonry and related sectors, replacing traditional scaffold systems. Under the Occupational Health and Safety Act (OHSA), employers and supervisors are required to take every precaution reasonable in the circumstances for the protection of workers (OHSA, clauses 25(2)(h) and 27(2)(c)). Parties must also comply with the requirements of the Construction Projects Regulation (O. Reg. 213/91).

Users of MCWP platforms should ensure that:

  • A MCWP is used only in accordance with the written instructions of the manufacturer.
  • A MCWP is not overloaded or used in a manner that would affect the platform’s stability or endanger a worker.
  • The rated working load of the MCWP is indicated on a sign visible to the operator at its controls.
  • A MCWP is maintained in such a way that the safety factors of the original design are maintained.
  • A MCWP is inspected each day before use, in accordance with the manufacturer's instructions.

The OHSA imposes the following requirements regarding the maintenance of equipment:

  • Employers must ensure that the equipment, materials and protective devices are maintained in good condition.
  • Suppliers of machines, devices, tools or equipment under any rental, leasing or similar arrangement must ensure that the items are maintained in good condition, if it is the supplier’s responsibility under the rental, leasing or similar arrangement to do so.

Best practices

CSA standard B 354.5-07(R2011), Mast-Climbing Work Platforms, provides current best practices for the design, manufacture, maintenance and testing of MCWP. However, based on the ministry’s recent observations of mast-climbing work platforms currently being used on construction projects, in addition to the annual inspection recommended in section 7.5 of CSA standard B354.5-07 it is recommended that:

  • The person doing the inspection be an engineer or be designated in writing as competent for the task by a professional engineer.
  • Critical welds be appropriately inspected, including using non-destructive testing in accordance with applicable methods recognized by the Canadian General Standards Board.

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This resource does not replace the Occupational Health and Safety Act (OHSA) and its regulations and should not be used as or considered legal advice. Health and safety inspectors apply and enforce these laws based on the facts they find in the workplace.