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Trench Shoring & Protective System Selector

OSHA 1926.652 decision-tree for excavation protection by soil type and depth

OSHA requires protective systems for all trenches 5 feet deep or greater, and recommends them for shallower trenches where conditions warrant. The standard (29 CFR 1926.652) gives employers four options: sloping, benching, shoring, and shielding. Which options are available depends on the soil classification and trench depth.

Soil classification is the critical first step. OSHA defines three soil types: Type A (most stable, such as caliche, hardpan, or stiff clay), Type B (medium stability, such as angular gravel or disturbed Type A), and Type C (least stable, such as granular sand or submerged soil). Each soil type has different maximum allowable slopes, benching configurations, and shoring load requirements. Getting the soil classification wrong can be fatal.

This tool walks through the OSHA decision tree step by step. Enter your trench depth, soil classification (or use the built-in identification guide), and groundwater conditions. The calculator shows which protective systems are permitted, the required slope angles or shoring pressures, and references to the applicable OSHA appendix tables.

Pro Tip: The biggest field mistake is classifying previously disturbed soil as Type A. Any soil that has been excavated and backfilled, even if it was originally stiff clay, is automatically Type B or worse. Trench collapses kill more construction workers per incident than any other hazard. When in doubt, classify one grade worse than you think — the cost of wider slopes or heavier shoring is trivial compared to a cave-in.

Calculate OSHA slope angles by soil type

Trench Sloping Calculator →

Estimate excavator production rates for the dig

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Check soil bearing capacity at the trench bottom

Soil Bearing Capacity Calculator →

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Trench Shoring & Protective System Selector
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How It Works

  1. Classify the Soil

    Use the built-in soil classification guide based on OSHA Appendix A. Answer questions about soil cohesion, plasticity, grain size, water conditions, and prior disturbance to determine Type A, B, or C.

  2. Enter Trench Dimensions

    Enter trench depth, width, and whether groundwater is present. Groundwater automatically downgrades Type A soil to Type C per OSHA rules.

  3. Review Permitted Systems

    The tool shows which protective systems (sloping, benching, shoring, shielding) are permitted for your soil type and depth. Each option includes the required dimensions, angles, or load ratings.

  4. Select and Document

    Choose a protective system and print the specification sheet for the competent person's documentation. Includes OSHA appendix references for each requirement.

Features & Capabilities

OSHA Decision Tree

Full OSHA 1926.652 decision tree with Appendix A soil classification guidance. Walks through the standard step by step.

Slope Angle Tables

Maximum allowable slopes per Appendix B: Type A (3/4H:1V, 53 degrees), Type B (1H:1V, 45 degrees), Type C (1-1/2H:1V, 34 degrees).

Timber Shoring Data

Tabulated timber shoring data from OSHA Appendix C covering trench depths from 5 to 20 feet.

Hydraulic Shoring Tables

Aluminum hydraulic shoring tables from OSHA Appendix D with waler spacing and cylinder sizing.

Trench Shield Ratings

Trench shield (trench box) minimum rating requirements calculated from soil lateral pressure at the specified depth.

Soil Type Rules

Automatic disqualification of benching for Type C soil per OSHA requirements. Groundwater presence auto-downgrades Type A to Type C.

References

  • Soil lateral pressure: Type A = 25 psf/ft depth, Type B = 45 psf/ft depth, Type C = 80 psf/ft depth
  • Maximum allowable slopes: Type A = 53 degrees (3/4H:1V), Type B = 45 degrees (1H:1V), Type C = 34 degrees (1-1/2H:1V)
  • Tabulated shoring data covers trenches from 5 to 20 feet deep
  • Trench box rating = soil unit weight x depth x spacing factor

Frequently Asked Questions

OSHA requires a protective system (sloping, benching, shoring, or shielding) for all trenches 5 feet deep or greater, unless the excavation is made entirely in stable rock. For trenches less than 5 feet, a competent person must determine if protection is needed based on soil conditions.
No. OSHA specifically prohibits benching in Type C soil. The only options for Type C soil are sloping at 1-1/2H:1V (34 degrees), shoring designed for 80 psf per foot of depth, or shielding with a trench box rated for the soil pressure.
Type A is the most stable: cohesive soil with unconfined compressive strength of 1.5 tsf or greater (stiff clay, caliche, hardpan). Type B has lower strength (0.5 to 1.5 tsf) or is granular cohesionless soil like angular gravel. Any previously disturbed soil (even if originally Type A) is automatically downgraded to at least Type B.
Disclaimer: This tool is an educational reference based on OSHA 29 CFR 1926.652 and its appendices. It does not replace a competent person's on-site evaluation. Actual soil conditions, surcharge loads, adjacent structures, and changing weather may require more conservative protective systems than the tabulated minimums. A registered professional engineer must design protective systems for trenches deeper than 20 feet.

Learn More

Safety

Trench Safety: OSHA Protective System Requirements

OSHA 1926.652 trench protection requirements explained. Soil classification, sloping angles, shoring options, and trench box selection by depth and soil type.

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