Trench Protective Systems — The 5 ft Rule

OSHA 1926.652 in one page: every excavation 5 ft or deeper, unless made entirely in stable rock — and under 5 ft, protection is still required when the competent person finds any indication of a potential cave-in. Below that trigger sit two menus of four design options each. Federal law, life-safety; the competent person makes the site calls, and state plans can be stricter.

Sloping & benching — the four design options

OSHA 1926.652(b)
Any one option satisfies the standard. Option 1 needs no soil classification; Options 3 and 4 put an engineer's stamp on the design.
OptionRuleCite
Option 1Slope everything at 1½H:1V (34°) — no soil classification required (the Type C worst case)652(b)(1)
Option 2Classify the soil per Appendix A and slope per the Appendix B tables652(b)(2)
Option 3Other written tabulated data approved by a registered professional engineer (copy on site)652(b)(3)
Option 4Site-specific design by a registered professional engineer652(b)(4)

Support & shield systems — the four design options

OSHA 1926.652(c)
The same four-option structure for shoring and shields. Option 1 is the OSHA appendices themselves; Option 2 — manufacturer tabulated data — is how nearly every trench box is actually deployed.
OptionRuleCite
Option 1Timber shoring per Appendices A and C; aluminum hydraulic shoring per Appendix D652(c)(1)
Option 2Manufacturer’s tabulated data (deviations only with the manufacturer’s written approval)652(c)(2)
Option 3Other written tabulated data approved by an RPE (copy on site)652(c)(3)
Option 4Site-specific design by an RPE652(c)(4)

Picking a system in practice

Room decides: open ground gets sloped (cheap, per the slope chart) or benched (benching chart); streets and tight easements get a box or shoring. Past 20 ft, every road leads to an engineer — the deep excavation rules cover that line. And whatever the system, the daily-driver rules of 1926.651 (quick rules) still apply on top.

Common questions

At what depth does a trench require protection?

5 feet — every excavation 5 ft or deeper needs a protective system unless it is cut entirely in stable rock. The under-5 framing matters just as much: a shallower trench still requires protection whenever the competent person finds any indication of a potential cave-in. "Under 5 ft is exempt" is not what the standard says.

Can you slope a trench without classifying the soil?

Yes — that is Option 1: slope everything at 1½:1 (34°), the Type C worst case, with no classification at all. It trades dirt for paperwork. The moment the cut gets steeper than 34°, someone is on the hook for a classification (Option 2), engineer-approved tabulated data (Option 3), or an engineered design (Option 4).

What counts as a protective system?

Three families: sloping/benching (cut the ground back so it cannot fall), support systems (shore the faces — timber or aluminum hydraulic per the OSHA appendices, or manufacturer tabulated data), and shields (trench boxes — which protect the workers inside rather than preventing the collapse). Each family has its own chart here, and each must resist every load that could reasonably reach it.