Formwork
Also called Shuttering, Shutters, Form work, Formwork and falsework
Formwork — shuttering, in most UK site usage — is the temporary mould that holds wet concrete in shape and carries its weight and its pressure until the concrete has gained enough strength to stand up on its own. It is a temporary works item like any other: designed, checked, briefed and permitted before it is loaded, and removed once it is no longer needed.
In practice
The parts have their own names and it is worth being able to use them. The soffit is the face the slab sits on; the sides are the vertical faces that contain a wall, beam or column; a stop-end is the shutter that closes the end of a pour, and so decides where the construction joint falls; a kicker is the short concrete upstand cast with the slab to locate the wall or column shutter that follows it. Falsework is the structure holding all of that up — props, frames, beams and their bases — and it is the half that carries the load down to something able to take it. Two quantities govern the design and neither is a site decision. The first is the pressure fresh concrete exerts on a vertical face, which rises with pour rate, temperature, workability and the admixtures in the mix. The second is striking time, which is a concrete strength question rather than a clock question. BS 5975-2:2024, Temporary works — Falsework: design and implementation, is the British Standard code of practice for the design side of it.
Where this comes from: UK site practice, framed against the temporary works regime. The design rules for falsework are in BS 5975-2:2024, a paywalled document; nothing from inside it appears here, and no pour rate, concrete pressure or striking time is given anywhere on this page, because those are design outputs for a specific pour rather than general figures.
Where it matters on site
The usual failure is not a collapse, it is drift. A shutter is reused from the last pour, the pump is going well so the pour rate goes up, an extra prop is left out because it was in the way — and the design that was done for the original arrangement is never re-checked against the arrangement actually standing there. If a shutter or its falsework has been altered, propped differently or loaded faster than the design assumed, it is a different temporary works item and belongs back with the temporary works coordinator before it is filled. The second recurring one is quieter: moving a stop-end to suit the day’s pour moves a construction joint, and construction joint positions are structural decisions about reinforcement continuity and shear transfer, not convenience. Our own shuttering products sit at the small end of this — the Instant Pipe Shutter for the annulus around a waste pipe, the Shutter Clip for the joint between hollowcore unit ends — where the traditional answer is a piece of timber cut on site and the risk being designed out is hand-arm vibration, silica dust and working at height rather than collapse.