When a CDZ is allowed
A controlled decking zone (CDZ) is an area where metal decking is first being installed and forms the leading edge. Under 29 CFR 1926.760(c), a CDZ may be set up only where leading-edge workers are over 15 ft and up to 30 ft above a lower level.
The traps:
- 6 to 15 ft is below the Subpart R trigger in 1926.760(a)(1), so no CDZ is needed there.
- Above 30 ft a CDZ is not allowed at all.
- 48 ft is the four-floor unfinished-bolting limit in 1926.754(b)(2), not a CDZ figure.
- Restricting access is one CDZ condition under (c)(2), but it does not remove the height limits.
Size and unsecured decking
Two separate limits apply, and they measure different things:
- Zone size, 1926.760(c)(3): no more than 90 ft (27.4 m) wide by 90 ft deep from any leading edge.
- Unsecured decking, 1926.760(c)(5): no more than 3,000 sq ft (914.4 m2) at one time, however large the zone is.
Worked example: a zone laid out at the full 90 ft × 90 ft covers 8,100 sq ft, but only 3,000 sq ft of it may be unsecured decking. Answering 8,100 sq ft confuses the zone's area with the decking limit.
Keep the look-alike numbers apart: 60 ft is the joist span in 1926.757(a)(3) that one employee can release without erection bridging; 4,000 lb is the decking bundle limit on joists in 1926.757(e)(4); 1,000 lb is the bridging bundle limit in 1926.757(e)(3).
Who and what is allowed inside
- Access is limited to leading-edge workers, 1926.760(c)(2).
- Those workers must have completed CDZ training under 1926.761, (c)(4).
- Each deck panel needs at least two safety attachments. That is a requirement, not a prohibited act.
- Final deck attachments and shear connectors may not be installed inside a CDZ. This is the one activity on the list that is barred.