Trench Boxes: Installing & Moving

A trench box (also called a trench shield) doesn’t hold the trench walls up. It protects the workers inside it if the walls cave in. It only works if it’s the right box for the depth and soil, set correctly, and workers stay inside it.

• Construction
• Pipe layers
• Equipment operators

Use the tabulated data

• Every box has manufacturer’s tabulated data showing the maximum depth it’s rated for in each soil type. Keep a copy at the jobsite.
• The box must be designed for the full depth of the trench and the soil conditions. See Soil Classification.
• Don’t load it beyond its design; that includes surcharge from equipment and spoil near the edge.

Setting the box

• Nobody inside the box while it’s being installed, removed or moved vertically.
• Limit side movement: set it so it can’t shift sideways in a cave-in; backfill gaps between the box and the trench wall if needed.
• Digging below the box: you can dig no more than 2 feet below the bottom of the box, and only if the box is designed for the full trench depth and there’s no sign of soil loss behind or below it.
• Above the box: if the trench is deeper than the box is tall, slope or bench the soil above it, or stack boxes as the maker allows. The top of the box should extend at least 18 inches above the surrounding soil where soil slopes toward it.
• Stacked boxes must be connected with the maker’s pins and connectors.

Working in the box

• Stay inside the box. The open ends and the area outside it are unprotected.
• Use a ladder inside the box to get in and out; there must be a way out within 25 feet in trenches 4 feet or deeper.
• Don’t ride the box or the bucket into or out of the trench.
• Watch the ends: soil can slough in from the open ends. Use end plates where needed.
• Get out before the box is dragged or lifted.

Inspect the box

A competent person inspects the trench and box daily and after rain or anything that could change conditions. Look for bent walls or spreaders, cracked welds, missing pins and damaged connectors. See Competent Person Inspections.

Last updated: October 2, 2026