Graphical Construction Glossary >> Temporary Work. >> formwork >> Back Propping

Back Propping

The technique of stripping the formwork in a suspended slab while still keeping it supported.

The structural engineer may require that a newly poured concrete slab should be supported by props for a certain amount of time until it has gained enough strength to support the loads to be imposed upon it.

At the same time the builder wants to strip the formwork and use it on the next slab.

The answer is to remove the formwork while at the same time never leaving the slab unsupported.

This is a fairly easy task, but it does take longer than just simply stripping the slab in the normal way and then sticking a few props up after everything has been cleared out.

For this reason or maybe because of ignorance a lot of formworkers do not back-prop correctly.

• The basic principal is to place the required number of extra props on the plywood only. before anything else is removed.
• Then, and only then, are the rest of the supports, beams, joists and the ply with no props holding it.
• New props are then placed under the bare concrete.
• Then the props that are left holding up just the ply sheets are removed one at a time, the ply is removed and the prop is put back against the concrete before the moving on to the next one.
• In this way the slab is always supported.

For non glossary articles of a general and how to nature go to the formwork section on this site.

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