Work at height means work in any place where a person could fall a distance liable to cause personal injury. That is the whole definition, and it is why there is no two metre rule in Great Britain: a fall from a low platform onto a spike or into machinery is work at height, and standing on a chair to change a light is too. Falls from height remain the single largest cause of workplace fatalities in Great Britain.
What the law asks first
Regulation 6 of the Work at Height Regulations 2005 requires that work is not carried out at height where it is reasonably practicable to do it safely otherwise. That question is asked before any discussion of ladders or harnesses. Bringing the luminaire down, specifying a fitting that can be maintained from ground level, or assembling at ground level and lifting the finished unit are all better answers than a safer way of going up.
The hierarchy after that
Where work must be at height, prevent falls: use an existing safe place of work, then collective protection such as guardrails, tower scaffold or a mobile elevating work platform, then personal fall prevention such as a work restraint that stops you reaching the edge. Only where a fall cannot be prevented do you move to minimising the distance and consequences, using nets, airbags or a personal fall arrest system. Collective before personal is the ordering principle throughout.
What the risk assessment has to deal with
The access and egress, the working platform and its edges, fragile surfaces, the weather including wind, falling objects and the people below, the duration of the task, the competence of the people doing it, and rescue. Rescue is the half most often missing: a worker suspended in a harness after arresting a fall has a limited time before suspension trauma becomes life threatening, and calling the fire service is not a rescue plan.
Fragile surfaces and the roof
Fragile roof lights and corroded sheeting kill people every year, usually in maintenance rather than construction. The assumption that a roof will bear weight because it looks solid is the recurring cause. Roof work needs the fragile areas identified before anyone goes up, physical protection over or under them, and edge protection, and it needs the assessment to have been made by somebody who saw the roof.
Duration is not a defence
Short duration work is where most falls happen, because the effort of setting up proper access feels disproportionate to a five minute job. The regulations make no exception for short tasks. The practical answer is having the right equipment easily available, because the barrier is almost never that people do not know what they should use.
Questions people ask about work at height
What is the definition of work at height?
Work in any place where, if precautions were not taken, a person could fall a distance liable to cause personal injury. It includes work at or below ground level and access and egress to a place of work.
What height is considered working at height?
There is no minimum height in GB law. The test is whether a fall could cause injury, not how far the fall is.
Is a ladder banned for work at height?
No. Ladders are permitted where a risk assessment shows the work is low risk and short duration, or where site features mean higher risk equipment cannot be used.
Does a rescue plan have to be written down?
The arrangements have to be planned and workable, and in practice that means written and rehearsed. A plan that consists of calling the emergency services is not a plan for someone suspended in a harness.