Temporary works fail more often than permanent structures for a straightforward reason: they carry real loads, they are assembled quickly by people who did not design them, and they are frequently treated as equipment rather than as structures.

What counts as temporary works

Anything provided to support, contain or give access during construction and then removed: falsework carrying wet concrete, formwork holding its shape, propping supporting a structure during alteration, excavation support, edge protection, hoarding resisting wind, a temporary ramp, a crane base, or a facade retention scheme. The common thread is that each one carries a load, and none of them appear on the permanent drawings, so nobody checks them unless the process explicitly requires it.

Why the failures cluster where they do

Temporary works fail at the moments of highest load and least attention: during concrete pours, when the load rises rapidly and the structure is doing exactly what it was designed for; and during striking, when props are removed in an order nobody planned. They also fail because of what was underneath them. A prop transmits its entire load into whatever it is standing on, and a prop bearing on a slab that has not gained strength, or on a floor with a void below, is not supported at all.

The load path has to continue all the way down

Propping a soffit transfers the load to the floor below, which then has to carry it or pass it on. Where the load is significant, the propping continues through successive floors until it reaches something that can take it, and each level has to line up with the one above. Props offset from the level below convert a direct path into a bending action on a slab that was never designed for it, and this is one of the most common defects found in temporary works inspections.

Design, check and permit to load

The process that prevents these failures is simple in outline: a design produced by someone competent, an independent check proportionate to the risk, an inspection confirming the works were actually built as designed, and a formal authorisation before the load is applied or before striking begins. The independent check exists because a designer cannot reliably check their own assumptions, and the permit exists because the gap between the design and what was built on a wet Friday afternoon is where the failures live.

Substitution and the missing pin

Temporary works components are designed as systems, and the parts are not interchangeable with whatever is to hand. A proprietary prop pin replaced with a bolt or a reinforcement bar, a coupler of a different type, a base plate omitted, or a component from a different system mixed into an assembly all reduce capacity by an amount nobody on site can calculate. These substitutions are almost always made in good faith to keep the job moving, which is why they need to be designed out by having the right parts on site rather than prohibited by instruction.

For excavation support specifically, see when an excavation needs support. For propping during structural removal, see demolition sequence and structural stability.

Related standards

The standards below set the test methods and performance levels behind the protective equipment used for this work.

• EN 397 — Industrial Safety Helmets
• EN ISO 20345 — Safety Footwear
• EN 361 — Full Body Harnesses

Frequently asked questions