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Trenches and excavations without shoring

Trenches and excavations are work areas that are hazardous for workers if they are not shored. In the construction sector, foundation work is the main hazardous task.

Workers are sometimes trapped or buried in trenches and excavations as a result of the walls caving in or a landslide. These accidents can cause fractures, internal bleeding, suffocation, crush syndrome or even death.

The employer is responsible for implementing preventive measures to provide safe working conditions for their work team when accessing a trench or excavation. Shoring is the best way to avoid any risk of a cave-in and ensure the safety of workers.

Safety rules

Zero tolerance

If any of these rules are not followed, the CNESST will stop the work and those at fault will be liable to criminal prosecution.

Fiche Tolérance 0 : Tranchées et excavations sans étançon (in French only)

During trench or excavation work, shoring is the best way to prevent a cave-in, but is not required in the following cases:

  • the trench or excavation is dug out of solid rock
  • workers are not required to enter the trench or excavation
  • there is no risk of the walls caving in and their slope is less than 45 degrees from a point less than 1.2 m from the bottom
  • there is no risk of the walls caving in and an engineer certifies that shoring is not necessary

Landslide hazard

There is a risk of a landslide

  • when the slope is greater than the angle of repose of the soil
  • when there are cracks in the soil
  • when there is bulging of the wall
  • when there is a significant amount of water, loose blocks or materials placed within 1.2 m of the top of the walls
  • when vehicles or machinery are driven or parked within 3 metres of the top of the walls
Other mandatory safety measures

Depending on the tasks to be performed, one or more of the following measures must be taken by the employer to ensure the safety of the worker:

  • shoring must comply with the plans and specifications of an engineer
  • materials must be placed more than 1.2 m from the top of the walls
  • vehicles and machinery must be driven or parked more than 3 m from the top of the walls, unless reinforced shoring has been used
  • shoring must extend 300 mm outside the trench or excavation, except when it is dug on a public road and it must be covered to allow for the passage of traffic during periods when work is not in progress
  • when workers are in a trench or excavation, the employer must post an experienced person at the surface to detect faults, falling rocks or any other source of danger
  • during the work, the employer must ensure that the walls are inspected and maintained so there are never any:
  • continuous barriers or barricades or a warning line must be set up at the top of any trench or excavation that is more than 3 m deep or that may constitute a hazard for workers or the public

Protective measures


When there is a risk of rock blocks coming loose or sliding off one of its walls, measures to eliminate the risk must be taken. Shoring is one such measure.

For a trench or excavation that is deeper than 6 m, before work begins, the employer must send the CNESST the installation and dismantling plans and procedures signed and sealed by an engineer from the shoring manufacturer.

Types of shoring

  • Prefabricated steel shoring
  • Timber shoring, built on site
  • Hydraulic shoring, pre-assembled or assembled on site
  • Custom made shoring

Laws and regulations