In construction, shoring means a temporary structure that supports something so it doesn't move or collapse. In excavation work, shoring supports the sides of the trench so the soil can't cave in. OSHA's definition (1926.650) calls it a structure such as a metal hydraulic, mechanical or timber shoring system that supports the sides of an excavation and is designed to prevent cave-ins.
(You'll also hear "shoring" for supports under formwork and slabs during concrete work, and for propping damaged structures. This guide is about trench and excavation shoring.)
Why choose shoring over a trench box or sloping?
Shoring prevents the wall from moving. That's why it's the go-to system when:
- The trench runs next to buildings, foundations, roads or sidewalks that could settle.
- Live utilities cross or parallel the trench and can't tolerate soil movement.
- There's no room to slope and no room to swing a trench box.
The main types at a glance
| System | How it works | Typical depth and use | Design basis |
|---|---|---|---|
| Aluminum hydraulic shores | Aluminum rails pressed against the walls by hydraulic cylinders, installed from the top | Utility and service trenches, often to about 15 to 20 feet | OSHA Appendix D or manufacturer's tabulated data |
| Timber shoring | Wood uprights, wales and cross braces | Short runs, odd shapes, to 20 feet per tables | OSHA Appendix C or a PE |
| Screw jacks (trench jacks) | Adjustable steel screw struts with timber or rails | Small, shallow jobs | Manufacturer's data or Appendix E alternatives |
| Pneumatic shores | Air-pressurized struts locked mechanically | Utility trenches | Manufacturer's tabulated data |
| Slide rail systems | Steel panels slide down vertical posts as excavation deepens | Deep pipe, pits, pump stations, wide trenches | Manufacturer's data and/or a PE |
| Sheet piling | Interlocking steel sheets driven before excavation | Deep, wet or soft soils, cofferdams | Engineered design |
| Soldier piles and lagging | Steel H-piles with timber or precast lagging placed as the dig deepens | Building excavations, deep cuts next to structures | Engineered design |
Aluminum hydraulic shoring
The workhorse of utility shoring. Each shore is two vertical aluminum rails connected by one or more hydraulic cylinders. A worker at the surface lowers the shore with a pole or the machine, then pumps fluid to extend the cylinders until the rails press against both walls.
Advantages: installed and removed without entering the trench, light enough to handle by hand or with a small machine, and the cylinders preload the soil. Appendix D sets maximum vertical and horizontal spacing by soil type and depth. In weaker soils the tables call for closer spacing, wales and sheeting such as plywood to stop raveling between shores.
Watch for: leaking cylinders, bent rails, missing or damaged pins, and shores spaced farther apart than the tables allow.
Timber shoring
Traditional timber shoring uses uprights against the walls, wales running along the trench, and cross braces spanning it. Appendix C tables give member sizes and spacing by soil type and depth up to 20 feet. Timber can be built to fit irregular shapes, but it takes skilled carpenters, more time, and care to make sure installers are always working from a protected position.
Screw jacks and pneumatic shores
Screw jacks (trench jacks) are adjustable steel struts used with uprights or wales. They're inexpensive and simple, but they're installed by hand and don't preload the soil the way hydraulic shores do. Pneumatic shores use air pressure to extend and then lock mechanically. Both must be used per the manufacturer's tabulated data. Appendix E illustrates several of these alternatives to timber shoring.
Slide rail shoring
Slide rail systems use vertical steel posts (rails) with heavy steel panels that slide down channels in the posts. The crew digs a little, pushes the panels down, digs again, and so on, keeping the support close to the bottom of the excavation. They handle deep, long or wide excavations and pits with large open spans for pipe and structures, and they're common on large sewer and pump station work. They're designed from manufacturer's data, often with a site-specific engineering review.
Sheet piling
Interlocking steel sheet piles are driven or vibrated into the ground before excavation, creating a continuous wall that also helps cut off groundwater. Deeper cuts use internal wales and struts or tiebacks. Sheet piling needs an engineer's design and attention to vibration effects on nearby structures.
Soldier piles and lagging
Steel H-piles (soldier piles) are drilled or driven at intervals, and horizontal lagging (timber or precast) is placed between them as the excavation deepens. Common for building basements and excavations next to existing structures. Engineered design required.
OSHA rules that apply to every shoring system
- Design under one of the four options in 1926.652(c): Appendices C and D, manufacturer's tabulated data, other approved tabulated data, or a registered professional engineer. Keep the data at the jobsite.
- Keep members securely connected to prevent kickouts, and never overload them.
- Install as you dig and remove from the bottom up, backfilling as you go.
- You may excavate up to 2 feet below the bottom of the support system only if it's designed for the full trench depth and no soil is lost from behind or below.
- A competent person inspects daily, after rain and after any event that changes conditions.
Choosing the right system
Learn the fundamentals in our free shoring systems lesson.
Sources and official references
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.