Trench Shoring Systems: Hydraulic, Timber and Engineered Shoring

Shoring is a support system that holds the trench walls in place so they cannot cave in. Unlike a trench box, which protects workers if the wall fails, shoring is designed to stop the wall from failing in the first place. That makes it the system of choice next to buildings, roads and existing utilities, where any soil movement causes damage.

The parts of a shoring system

A kickout is the accidental release or failure of a cross brace, one of the main reasons OSHA requires members to be securely connected.

Aluminum hydraulic shoring

Aluminum hydraulic shores are the most common shoring in utility work. Each shore is a pair of aluminum rails connected by hydraulic cylinders. A worker standing outside the trench lowers the shore into place and pumps the cylinders to press the rails against the walls.

Why crews like it:

• It is installed and removed from the top, so nobody enters an unprotected trench.
• It is lightweight and fast to move along a pipe run.
• The cylinders preload the soil, actively restraining it before it starts to move.

Appendix D to Subpart P gives tabulated data for aluminum hydraulic shoring by soil type and depth, including maximum vertical and horizontal spacing of shores and when wales or sheeting (such as plywood) are needed to control raveling. Manufacturers also publish their own tabulated data, which must be followed.

Timber shoring

Timber shoring uses wood uprights, wales and cross braces sized from the tables in Appendix C, which cover soil Types A, B and C to 20 feet deep. Timber is still used for odd shapes, short runs and places where hydraulic shores do not fit, but it is labor-intensive and installers must work from a protected position. Appendix E shows alternatives to timber shoring such as hydraulic, pneumatic and screw-jack systems.

Other engineered systems

Deep, wide or wet excavations often use systems that need manufacturer or engineer design:

• Slide rail systems: steel panels that slide down vertical posts as the excavation deepens.
• Sheet piling: interlocking steel sheets driven before digging, common in water-bearing soils.
• Soldier piles and lagging: steel H-piles with timber or concrete lagging between them.

See our guide to the types of trench shoring for a side-by-side comparison.

How shoring must be designed

1926.652(c) gives four design options for support systems, shields and other protective systems:

1. Appendices A, C and D: classify the soil, then use the timber or aluminum hydraulic tables.
2. Manufacturer's tabulated data: use the system exactly as the manufacturer specifies. Any deviation needs the manufacturer's specific written approval, and the data must be kept at the jobsite during construction.
3. Other tabulated data: tables approved by a registered professional engineer, kept at the jobsite.
4. Design by a registered professional engineer: a written design, kept at the jobsite.

Installing and removing support systems

1926.652(e) sets the rules:

• Members must be securely connected to prevent sliding, falling, kickouts or other predictable failure.
• Install and remove support systems in a way that protects workers from cave-ins and structural collapse.
• Never load a member beyond what it was designed for.
• Before temporarily removing any member, take additional precautions, such as installing other structural members.
• Removal starts at the bottom of the excavation and works up. Members are released slowly, and workers watch for signs of possible failure.
• Backfilling progresses together with removal of support systems.
• Installation is closely coordinated with excavation, so the trench is never dug far ahead of the shores.
• Excavating up to 2 feet below the bottom of the support system is allowed only if the system is designed for the full depth of the trench and there is no sign of soil loss from behind or below it.

Key takeaways

• Shoring holds the walls in place. Shields protect workers if a wall fails.
• Components: uprights, wales, cross braces and sheeting.
• Aluminum hydraulic shoring is installed and removed from outside the trench and preloads the soil.
• Designs come from Appendices C and D, manufacturer's data, other approved tables, or a PE, and the data stays on site.
• Install as you dig, remove from the bottom up, and backfill as you go.

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.