March 29, 2018

Control Zones – An Underrated Option for Rooftop Safety

What Is a Control Zone?

A control zone is the interior part of a large low-rise roof (4 degrees horizontal rise or less, according to Alberta Labour), which is at least 2 metres in from the edge. Specific standards on this are difficult to find, as not all provinces have officially defined what they consider to be the control zone.

That’s why we wanted to bring you an article on this. The “control zone” concept offers a method of indicating a safe distance from the roof edge. At W.S. Safety, we see this concept as a missed asset. If you have a large roof, there may not even be any need to invest in an anchor system at all. Instead, marking out the zone might be all that is needed.

Anchor Systems vs. Warning Lines

Many rooftop construction projects in Canada currently include the installation of permanent anchor systems with harnesses. While this anchor system is widely accepted and approved, there are some drawbacks.

Drawbacks of anchor systems

  • Require holes to be drilled in the roof
  • Require annual inspection
  • Require harness training for any roof workers
  • Can negate the roof warranty (if the warranty is a “manufacturer’s material warranty”)

With these drawbacks, a close look at Canadian regulations will show that an alternate system is available. This system is based on the “control zone” regulation.

Often “warning lines” can just as effectively serve this purpose. W.S. Safety offers two types of warning lines: Tech-Flag and PermaLine.

Benefits of warning lines

  • Less expensive
  • Less setup time needed
  • Do not need to be inspected as often
  • Do not require specific training for workers who go up onto the roof
  • Can be non penetrating (as are Tech-Flag and PermaLine)
  • Do not negate your roof warranty

Control Zone Options

The Canadian Centre for Occupational Health and Safety states, “Control zones involve setting raised warning lines at a safe distance ” 2 metres (6.5 ft.) ” from unguarded edges” (2015).

In codes province to province, there is a middle zone of the roof called a “control zone.” These are generally 2 metres from the roof edge, as are all of the provinces, for example, below.




Alberta Labour


WorkSafe BC


Occupational Health and Safety


General Health and Safety Requirements


Fall Prevention and Roof Safety Program


Fall Protection Guide


Queen’s University Environmental Health & Safety

Instead of making anchor systems your “go to choice,” the control zone system gives rooftop options to fit your budget.

Further, the According to Manitoba’s Workplace Safety and Health Division, “If working outside the warning barrier/control zone, the lifeline of the fall-arrest system must be secured to an anchor.” This then only requires a lifeline for workers who go beyond the barrier/control zone.

For example, if HVAC maintenance has to be performed periodically on top of a large flat roof, and the unit is not close to the edge of the roof, it is possible to install warning flags to demarcate a “control zone” and then to install another set of warning flags to demarcate a buffer zone. (A buffer zone, according to The Department of Environmental Health & Safety of Queen’s University, is “The (2) two meter border around the edge of a flat roof or platform.” The central zone is then called the “safe zone.”)

Why Setup a Control Zone?

The Occupational Health and Safety Guidelines for Farming Operations in Ontario states that a fall protection system is, “A system designed to protect workers from the risk of falling between levels when working at heights. Examples of fall protection systems include safety harnesses and lifelines; the use of guardrails or barriers; and, travel restraints that limit a worker’s movement to a safe area.”

Here the Ministry offers “barriers” as an acceptable form of fall protection. This highlights the option of using warning flag systems.

Features of Tech-Flags

  • OSHA compliant
  • Zinc-plate steel base, to blend in with the building when looking from the ground
  • Comes with a pin for quickly securing post to base
  • Non penetrating

Features of PermaLine

  • OSHA compliant
  • Highly visible warning barrier
  • Designed for permanent placement on a roof
  • Non penetrating

W.S. Safety offers

  • Quick response times
  • Quality, certified products
  • Excellent pricing with options to suit your budget
  • Compliant product with the relevant standards and codes for individual areas

This article is based on the research and opinion of the writer and should not be used as legal advice.

Related Links:

What You Should Know About Roof Warranties. Highland Commercial Roofing.

Part 9 Fall Protection. Section 161 Control zones. Alberta Labour. July 2009.

Guidelines Part 11 – Fall Protection. WorkSafe BC.

The Occupational Health and Safety Regulations, 1996.

General Health and Safety Requirements. Government of Newfoundland and Labrador 2014.

Fall Protection Guide. Manitoba. p. 57. May 2011.

Fall Prevention and Roof Safety Program. March 2004.

Queen’s University Environmental Health & Safety. May 2016.’s/SOP-Safety-18__roof_access.pdf

Health and Safety Report. Canadian Centre for Occupational Health and Safety. April 2015.

About W.S. Safety.

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