When concrete formwork and shores may be removed

Concrete reaching a certain age does not by itself authorize stripping forms or shores. The controlling question is whether the concrete can safely carry its own weight and the superimposed loads after support is removed.

Two permitted bases for removal

OSHA §1926.703(e)(1) requires the employer to determine that the concrete has gained sufficient strength. The determination must be based on one of two routes: the plans and specifications state the conditions for removing forms and shores and those conditions have been followed; or the concrete is properly tested using an appropriate ASTM standard test method designed to indicate compressive strength, and the results show sufficient strength. The rule does not establish one universal waiting period for every mix, span, temperature, or loading condition.

Consider the actual loads

The concrete must support both its own weight and superimposed loads. Those loads can include workers, stored materials, construction equipment, and loads from upper floors or later phases of work. If the construction sequence changes or the expected loads increase, a calendar-based assumption is not a substitute for checking the design conditions and capacity.

Reshoring has a separate removal threshold

When original forms and shores are removed, reshoring must be erected whenever the concrete is required to support loads beyond its capacity. Under §1926.703(e)(2), reshores cannot be removed until the concrete being supported has adequate strength to carry its own weight and all loads then in place. The sequence must maintain support; taking away shores first and planning to add reshores later defeats the purpose.

Do not confuse inspection with permission to strip

Shoring is inspected before erection and immediately before, during, and immediately after concrete placement under §1926.703(b). These inspection points check the shoring system and do not replace the separate strength determination required before form and shore removal. A sound shore can still be supporting concrete that is not ready to stand without it.

Exam traps

• Treating a fixed number of hours or days as OSHA's universal stripping rule.
• Checking only concrete self-weight and ignoring loads placed on the structure.
• Removing reshores before the supported concrete has adequate capacity.
• Confusing pre-pour shore inspections with the post-cure removal decision.
• Assuming the absence of visible cracking proves adequate compressive strength.

Key takeaway

Remove support only after a documented strength basis shows the concrete can carry its weight and current loads. Follow the specified plans or qualifying test results, and keep reshores until their supported concrete is ready.