Concrete Formwork: Safe Removal and Stripping

Tips & Advice

The beauty of engineered formwork is its durability. Unlike conventional formwork (usually wood), concrete formwork does not warp, shrink or swell with temperatures or varying weather conditions.

Though the up-front investment may be higher for engineered formwork over conventional, the return on investment is very high. For one, engineered formwork can be reused up to 2,000 times if the material is properly maintained. Second, it saves valuable time during set-up and tear down. Engineered formwork is already shaped and reinforced; conventional formwork often needs to be measured, cut, put into place, and secured before it can be used. Engineered formwork also requires less on-site labor.

Taking down, or stripping, formwork is also a less costly endeavor with engineered material. It’s not a task without risks, however. If removed incorrectly, or done without care, severe injuries can occur. Workers have strained muscles, injured limbs, and been crushed removing formwork.

Formwork should be left as long as possible, as its insulation helps in curing the concrete, but when the time comes to strip engineered formwork structures, here are 5 things to keep in mind.

Ensure the Concrete is Cured

We’ve previously discussed wait times for removing concrete formwork The curing of concrete is actually defined as “providing adequate moisture, temperature, and time to allow the concrete to achieve the desired properties for its intended use.” This is different from simply letting concrete dry, which is to allow concrete “to achieve a moisture condition appropriate for its intended use,” for things like flooring.

The curing process requires monitoring and maintenance of moisture and temperature within the formwork. For this reason, it’s very important to leave the formwork in place as long as possible. Generally, the American Concrete Institute recommends the following:

  • ASTM C 150 Type I cement seven days
  • ASTM C 150 Type II cement ten days
  • ASTM C 150 Type III cement three days
  • ASTM C 150 Type IV or V cement 14 days
  • ASTM C 595, C 845, C 1157 cements variable

Keep in mind that climate, temperatures, and the type of concrete (not to mention the size and shape of the concrete structure) can all impact the length of time it takes for concrete to set.

Step-by-Step

  1. Begin by stripping the face of walls and the sides of beams and columns first. These pieces of formwork are not load-bearing; their purpose is simply to hold the concrete in place. This process can typically begin at around 48 hours.

  2. Second, begin to remove the soffit, or underside, of slabs. This can begin around day 3 or 4. Props should be left under the slabs at this time.

  3. The beam soffits can be removed at around day 7.

  4. At around day 14, the props supporting the slabs can be examined for removal. Whether or not the props can be removed will depend on the size of the slab.

  5. Props for beams and arches should always be removed last. For spans under 20 feet, the recommended wait time is 14 days. For spans 20 feet or greater, wait at least 21 days.

All of the times above are estimated based on Ordinary Portland Cement usage. Always follow the advice of the engineer. Once the concrete formwork is removed, the structure should be able to withstand twice the stress it may be subjected to at the time of formwork removal

Important things to keep in mind:

Formwork Removal Should NOT…

  • Happen before the concrete is completely cured
  • Occur in a busy work zone; when working at an elevated level, there’s always a chance tools or debris can fall and injure someone below
  • Happen all at once; it’s best to avoid transferring the entire load to the structure at the same time
  • Damage the structural member upon removal; remove formwork slowly and carefully

Buy and Sell Used Concrete Formwork with Eiffel Trading

We have a large selection of used concrete formwork for sale.

All of our listings are constantly being updated, but if you don’t see what you’re looking for, create a wanted listing for free.

Ready to sell your used heavy equipment or construction material? List your products today for free on Eiffel Trading’s online marketplace.

If you have any questions or would like additional information, please call us at 1-800-541-7998 or email sales@eiffeltrading.com.