Concrete Formwork and Shoring Failures

Why it matters

Wet concrete is a liquid that weighs 150 pounds per cubic foot, and formwork is the dam holding it back. When forms or shores fail, they fail suddenly, dropping decks and blowing out walls with crews on top and underneath. OSHA requires formwork designed, installed, and removed under proper supervision. Today we cover what the crew controls: installation to the drawings, inspection during the pour, and never stripping early.

Hazards

• ⚠ Shore legs on mud sills that settle or on frozen ground that thaws
• ⚠ Missing cross-bracing turning shore towers into dominoes
• ⚠ Pour rates faster than the wall form design pressure
• ⚠ Vibrating close to form ties and blowing out panels
• ⚠ Stripping forms before the concrete reaches strength
• ⚠ Reshores omitted under fresh decks loaded with material

Controls and safe practices

• ✓ Erect formwork and shoring to the drawings: spacing, bracing, and bearing exactly as designed.
• ✓ Firm bearing under every shore: sills sized for the soil, no shimming with scrap.
• ✓ Watch during the pour: a designated worker monitors forms and shores and can stop the pour.
• ✓ Respect the design pour rate on walls and columns; fast pours multiply pressure.
• ✓ Strip only on the supervisor go-ahead based on strength data, not the calendar.
• ✓ Reshore per plan before loading fresh decks with material or equipment.
• ✓ Report any settlement, lean, or crushing sound immediately and clear the area.

Crew discussion questions

1. What are our shore spacing and bracing requirements on this deck, and do they match what is built?
2. Who watches the forms during the pour, and how do they stop it?
3. What tells us the concrete has reached stripping strength?
4. Where are we storing material on fresh decks, and is it over reshores?

Applicable OSHA standards

29 CFR 1926.703

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