The Definition of Controlled Access Zone (CAZ)

Definition of Controlled Access Zone (CAZ)

A controlled access zone (CAZ) is an area in which certain construction work may take place without guardrails, personal fall arrest systems or safety nets, and where access is controlled. OSHA defines it in 29 CFR 1926.500(b). The zone is usually marked by a control line set back from an unprotected or leading edge, and only workers who are authorized to do the specific work are allowed inside.

A CAZ does not stop a fall. It is an administrative control that limits who is exposed to the edge. For that reason, OSHA permits controlled access zones only in specific situations, such as overhand bricklaying, certain leading edge work and precast concrete erection, and work covered by a written fall protection plan when conventional fall protection is shown to be infeasible or more hazardous.

When a Controlled Access Zone Can Be Used

• Overhand bricklaying: Under 1926.501(b)(9), workers doing overhand bricklaying 6 feet or more above lower levels may be protected by a CAZ instead of guardrails, nets or fall arrest, as long as they do not reach more than 10 inches below the level of the walking surface.
• Fall protection plans: Under 1926.502(k), when an employer can show that conventional systems are infeasible or create a greater hazard for leading edge work, precast concrete erection or residential construction, the written plan must use a CAZ for workers not protected by conventional systems.
• Leading edge areas: A control line set for leading edge work can also stand in for a guardrail along the edge that parallels it, for workers nearby who are not doing leading edge work.

OSHA Requirements for Controlled Access Zones

Control Line Placement

Under 29 CFR 1926.502(g), when control lines are used:

• Leading edge work: The control line must be set not less than 6 feet nor more than 25 feet from the unprotected or leading edge, except during precast concrete erection.
• Precast concrete erection: The line must be not less than 6 feet nor more than 60 feet from the leading edge, or half the length of the member being erected, whichever is less.
• Overhand bricklaying: The line must be not less than 10 feet nor more than 15 feet from the working edge.
• Coverage: The line must run the entire length of the unprotected or leading edge, roughly parallel to it, and connect on each side to a guardrail system or wall.

Control Line Construction

• Ropes, wires, tapes or equivalent materials with supporting stanchions.
• Flagged or otherwise clearly marked at intervals of no more than 6 feet with high-visibility material.
• The lowest point, including sag, no less than 39 inches and no more than 45 inches above the walking surface, or up to 50 inches during overhand bricklaying.
• A minimum breaking strength of 200 pounds.

Access Rules

Only workers engaged in the permitted work may enter the zone. On overhand bricklaying jobs, additional control lines must be set on each side to enclose the zone, and no materials other than those being used may be stored there. Where a CAZ is part of a fall protection plan, a safety monitoring system is often used to watch workers inside the zone.

Good Practices for Controlled Access Zones

• Use it only where allowed: A CAZ is not a general substitute for guardrails or harnesses. Confirm the work falls within OSHA's permitted uses.
• Keep the zone small: Limit the number of workers inside to those who truly need to be there.
• Brief everyone on site: Other trades should know what the control line means and that they may not cross it.
• Inspect daily: Check that stanchions, flags and line height are still correct after wind, deliveries and moving equipment.
• Move the line with the work: As the leading edge advances, reposition the control line so the distances stay within limits.

Example of Controlled Access Zone (CAZ)

A masonry contractor is building an exterior wall on the fourth floor of a concrete-frame building using overhand bricklaying from the slab. The foreman sets a control line 12 feet back from the working edge with stanchions every few feet, flags at 5-foot intervals and the line at 48 inches above the slab. Side lines enclose the zone, and a sign at the entrance states that only bricklayers on the crew may enter.

During the afternoon, an electrician steps over the line to reach a junction box near the slab edge. A mason stops him, and the foreman reviews the access rules with the general contractor so other trades schedule work near the edge after the masonry crew moves on and guardrails are reinstalled.

Frequently Asked Questions: Controlled Access Zone (CAZ)

Is a controlled access zone a form of fall protection?

It is a recognized fall protection method only in the limited situations OSHA allows. It works by restricting access, not by stopping a fall.

How far from the edge must a control line be?

For leading edge work, between 6 and 25 feet. For overhand bricklaying, between 10 and 15 feet. Precast concrete erection has its own range.

Can any worker enter a CAZ?

No. Only workers engaged in the specific work the zone was set up for may enter, and they must follow the employer's fall protection plan or work rules.

How is a CAZ different from a warning line system?

A warning line system is used on low-slope roofs during roofing work. A CAZ is used for leading edge work, overhand bricklaying and work under a fall protection plan, and has different distance and height rules.