Every October the same question comes up in the site shed: at what temperature do we down tools? The answer surprises a lot of crews. Here is where the law sits, why heat and UV are separate hazards, and how to write controls for both into the SWMS so hot days are planned for rather than argued about at smoko.
There is no legal stop-work temperature on Australian sites. Safe Work Australia and the state regulators are consistent: WHS laws do not set a maximum temperature at which work must stop. What the law sets is a duty to manage the risk – heat is identified, assessed and controlled like any other hazard on the job.
That matters for the SWMS. High risk construction work done in hot conditions – roof sheeting, work at height, trenching, concreting – carries heat and UV hazards on top of those the SWMS already covers. In summer, those controls belong in the method statement, not in a verbal reminder at the pre-start.
Under section 19 of the WHS Act, the primary duty of care, a PCBU must ensure, so far as is reasonably practicable, the health and safety of workers. Heat sits squarely inside that duty. Section 49 adds the duty to consult workers – and the crew on the tools in January usually has the clearest view of which tasks are the problem.
The model WHS Regulations get more specific. Regulation 40(e) requires ventilation that lets workers do their work without risk to health and safety; regulation 40(f) requires that workers in extremes of heat or cold can work without risk to their health and safety. Regulation 41 requires adequate and accessible facilities for workers, including drinking water.
Workers also have a right, under the WHS Act, to cease or refuse to carry out work if they have a reasonable concern that it would expose them to a serious risk to their health or safety. A well-written SWMS makes that conversation easier, because the stop-and-reassess triggers are already agreed.
The key guidance document is Safe Work Australia’s guide, Managing the risks of working in heat. The controls below follow its approach.
Sun and heat behave differently and need separate controls. Heat stress comes from the combination of air temperature, humidity, radiant heat from the sun and hot surfaces, physical effort, clothing and how acclimatised the worker is. Heavy lifting in a tight ceiling space is a very different risk from the same day on an open, breezy slab.
UV radiation is not related to temperature at all. It can be high on cool and overcast days, when nobody feels the need for a hat. SunSmart guidance recommends sun protection whenever the UV Index is 3 or above, which covers most of the working year. A SWMS that only talks about heat leaves UV uncontrolled on the mild, cloudy days when crews skip the sunscreen.
Work through the hierarchy of control: remove or reduce the exposure first; PPE is the last line, not the first.
Three short examples of how that looks written into a job step:
Roof sheeting: sheets laid from first light, with a hard stop on sheet handling through the afternoon peak on forecast hot days; a shaded rest point at the access ladder; cool water carried up with the fixings; long sleeves, brimmed hard hats and sunscreen as standard; buddy pairs on each run.
Concrete pour: an early slot; shade cloth over the finishing area; a second finisher rostered so no one works the screed alone; water and shade at the pour, not at the gate; the supervisor holds the call on pausing if conditions deteriorate.
Trench work: shields and benching already in the SWMS, plus ventilation checks on still days when heat collects in the excavation; rotation between trench and surface; shade beside the excavation; a spotter watching for heat illness as well as ground movement.
Heat illness is a progression, and the early stages are easy to wave away. Heat rash and cramps come first. Next is heat exhaustion: heavy sweating, pale and clammy skin, headache, dizziness, nausea, a weak and rapid pulse and a worker who is clearly not themselves. Left alone, it can tip into heat stroke, where the body stops regulating its temperature: hot and often dry skin, confusion, slurred speech, staggering, collapse or seizures.
Heat stroke is a medical emergency. Call 000 straight away. While you wait, move the worker into shade or somewhere cool, remove excess clothing, and cool them with water, wet cloths and fanning. For the earlier stages, stop work, rest in the shade, cool down and sip water, and do not send the worker back until fully recovered. Write these actions into the emergency section of the SWMS so the crew is not working it out from memory.
Controls on paper only count if the crew knows them. On forecast hot days, open the pre-start with a short hot-weather toolbox talk: the plan for the heavy tasks, where the water and shade are, who is buddied with whom, and the signs to watch for. Our guide to toolbox talks that back up your SWMS covers how to keep them short and record them, and the Toolbox Talk generator will produce a heat-specific talk you can run from the phone.
A forecast heatwave is also a change in conditions. If the SWMS was written in winter and the job is now running through extreme days, the controls need checking against what is happening on site – a review trigger, not a judgment call. See when a SWMS must be reviewed or updated for how to handle the revision and re-sign.
Is there a temperature where work must stop?
No. Australian WHS laws do not set a maximum working temperature. The duty is to manage the
risk from heat, so far as is reasonably practicable, which is why the controls above belong in
the SWMS rather than a single number.
Can workers refuse to work in extreme heat?
Under the WHS Act, a worker may cease or refuse to carry out work if they have a reasonable
concern that it would expose them to a serious risk to their health or safety. Agreeing the
heat triggers in the SWMS means that decision is made together, early, not on the roof.
Do I need a separate SWMS for heat?
No. Heat and UV are hazards of the task in the conditions it is done in, so they go into the
SWMS for that high risk construction work as extra hazards, controls and emergency steps.
Two clear lines in a SWMS the crew has signed beat a separate heat document nobody reads.
How much water should workers drink?
There is no single figure that suits every worker, task and day. The practical rule is cool
water readily available at the work front, drunk regularly and before anyone feels thirsty,
more often as heat and effort increase. Follow Safe Work Australia’s guidance on working
in heat.
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