Striking a scaffold: where dismantling goes wrong

Erection gets the attention. Dismantling carries a comparable risk profile and rather less planning, partly because the structure already exists and looks finished, and partly because it happens at the end of a job when everybody has mentally moved on.

You are working on a structure you did not build

The scaffold being struck is frequently not the one that was erected. It has been adapted, possibly by more than one gang, possibly by other trades. Ties may have been moved. Sections may have been altered to get plant through. A gang arriving to dismantle is working on a structure whose current configuration nobody has necessarily written down.

Which makes the adaptation record operationally important at exactly the moment it is least likely to be consulted. A pre-strike inspection — walking the structure before touching it — is the practical substitute where the record is thin.

Sequence matters more, not less

On the way up, removing the wrong component is usually obvious because the thing you need is not there yet. On the way down, components can be removed in an order that leaves the remaining structure unstable, and it is not always visible that it has happened. Ties in particular: removing them ahead of the lifts they restrain is the classic error.

In practice: the strike that ran into Friday afternoon

A strike planned for a full day runs late. At four on a Friday there are two lifts left, a lorry booked, and a gang who would rather finish than come back Monday. The decision to push on is made by people who are tired, and the controls that get shortened are the ones that cost time.

Programming strikes so they do not finish against a deadline is unglamorous scheduling and removes the pressure that produces most of these decisions.

Common mistakes

• –Planning the strike as though the structure matches its original drawing
• –No pre-strike inspection where the adaptation record is thin
• –Removing ties ahead of the lifts they restrain
• –Dropping components rather than lowering them, because the job is nearly done
• –Scheduling a strike to finish against a hard deadline
• –Not updating the register when the structure comes down

Materials coming down are their own hazard

A strike generates a continuous stream of components that have to get to ground level, and the exclusion zone below is doing more work than during erection because the flow is heavier and more constant. Dropping is the obvious failure; a zone that was set up correctly and then encroached on by a delivery or another trade is the commoner one.

Where a structure stands over a footway, the highway licence conditions still apply during the strike — often the point at which pedestrian routing is most disrupted and least supervised.

Getting this right

Update the register as the structure comes down, not weeks later. A struck structure left on the list generates chasing for inspections that cannot happen, and once people learn to ignore that discrepancy the register stops being trusted for anything.

• –Walk the structure before touching it where the adaptation record is thin
• –Keep the exclusion zone supervised, not just established
• –Lower components rather than dropping them, however near the end you are
• –Do not schedule a strike to finish against a hard deadline
• –Maintain licence conditions during the strike, not just while standing
• –Record the strike immediately so the register stays true

Where this connects: the exclusion zone during a strike

A strike produces a continuous flow of components to ground level, heavier and more constant than anything during erection. The obvious failure is dropping. The commoner one is a zone established correctly at the start and then encroached on — by a delivery, another trade, or a client's own staff who were not told.

Where the structure stands over a footway, the highway licence conditions apply throughout the strike, and it is frequently the point at which pedestrian routing is most disrupted and least supervised. Supervising the zone rather than merely establishing it is the whole control.

• –Supervise the exclusion zone, do not merely establish it
• –Brief other trades and the client's staff, not only your own gang
• –Maintain licence conditions during the strike, not just while standing
• –Lower components however near the end of the job you are
• –Do not schedule a strike to finish against a hard deadline
• –Update the register the same day the structure comes down

One practical test: read the adaptation log before you start

Before a gang touches a structure that is coming down, read its adaptation history. If the log is thin or absent, that is the signal to walk the structure first rather than to work from the original drawing.

The specific thing to look for is ties: whether any have been moved, added or removed since erection, and whether the sequence the gang is planning accounts for where they actually are now rather than where they were drawn. Removing ties ahead of the lifts they restrain is the classic error, and an out-of-date drawing is how a competent gang makes it.