Sloping and Benching: OSHA Appendix B Ratios, Angles and Worked Examples

Sloping protects workers by cutting the walls back so they cannot collapse into the excavation. Benching does the same job with a series of steps. Neither needs equipment, but both need room, and both depend completely on a correct soil classification.

Reading a slope ratio

OSHA writes slopes as horizontal to vertical (H:V). A 1½:1 slope means that for every 1 foot of depth, the wall must lay back 1½ feet horizontally. The angle in parentheses is measured from the horizontal.

These slopes apply to excavations 20 feet deep or less. Sloping or benching for anything deeper must be designed by a registered professional engineer.

Calculating the setback and top width

The math is the same for every soil type:

• Horizontal setback on each side = depth × H value
• Top width = bottom width + 2 × setback

Notice how fast the footprint grows. A 10-foot Type C cut needs a 34-foot-wide opening, which is why sloping often isn't practical next to roads, buildings and other utilities. Try your own numbers in the trench slope calculator.

Remember the 2-foot rule too: spoil and equipment must stay at least 2 feet back from the top edge of the slope, not the trench bottom.

Short-term slopes in Type A soil

Appendix B allows a steeper ½:1 (63°) slope in Type A soil for excavations 12 feet deep or less that are open for 24 hours or less (short-term exposure). For short-term excavations deeper than 12 feet in Type A soil, the maximum slope is ¾:1.

When the actual slope must be flatter

The maximum allowable slope is a ceiling, not a target. Appendix B requires a flatter slope when:

• Signs of distress appear (cracks, bulging, sloughing). The slope must be cut back to at least ½H:1V flatter than the maximum. A Type B slope of 1:1 would become 1½:1.
• Surcharge loads from spoil, stored material, equipment or traffic are present. The competent person decides how much flatter the slope must be.

Option 1: the simple default

Under 1926.652(b)(1), an employer who has not classified the soil can slope at no steeper than 1½:1 (34°), the Type C slope, in the Type C configurations shown in Appendix B. It wastes some digging, but it removes classification errors from the equation. The other options are Appendices A and B (classify, then slope), other tabulated data approved by an engineer, or a design by a registered professional engineer.

Benching

Benching cuts the wall into steps instead of a smooth slope. The rules:

• Type A: benching is allowed. The overall slope from toe to top cannot be steeper than ¾:1.
• Type B: benching is allowed in cohesive Type B soil only. The overall slope cannot be steeper than 1:1.
• Type C: benching is not allowed.

Appendix B's figures also limit the height of each vertical step and of any unsupported vertical side at the bottom of the cut. Use the figure that matches your soil type and configuration, and do not freehand bench heights.

Working on slopes

1926.652(f) bars employees from working on the faces of sloped or benched excavations above other employees unless the workers below are protected from falling, rolling or sliding material.

Key takeaways

• Max slopes under 20 feet: stable rock vertical, Type A ¾:1, Type B 1:1, Type C 1½:1.
• Setback = depth × H value. Top width = bottom width + twice the setback.
• Type A can use ½:1 for short-term excavations 12 feet or less.
• Signs of distress require at least ½:1 flatter. Surcharges also require flattening.
• Benching: yes in Type A and cohesive Type B, never in Type C. Anything over 20 feet needs an engineer.

Last reviewed: October 25, 2026 · Free general education based on OSHA 29 CFR 1926 Subpart P. It does not replace the site-specific training and competent person your employer must provide, and it does not issue a certificate. Nothing you enter on this page is saved or sent.