Heat on site: is it time for a maximum working temperature?

Current legislation offers no upper temperature limit for construction work. The Workplace (Health, Safety and Welfare) Regulations 1992 specify minimum temperatures for indoor workplaces, but no equivalent ceiling exists.

That omission is not an oversight. Many industries routinely operate in high-temperature environments, from welding operations to boiler rooms and industrial plants. Introducing a fixed maximum temperature could make some essential activities technically impossible to undertake legally.

However, the absence of a temperature threshold should not be mistaken for an absence of responsibility.

Under the Health and Safety at Work etc. Act 1974, employers must ensure, so far as is reasonably practicable, the health, safety and welfare of their employees. That duty is reinforced by the Management of Health and Safety at Work Regulations 1999, which require employers to identify workplace hazards and implement appropriate controls.

The legal question, therefore, is not “how hot is too hot?” but rather “what are employers doing to manage the risks?”

This risk-based approach has advantages. Construction is an incredibly diverse industry. A site worker carrying blocks in direct sunlight faces very different challenges from a crane operator in an air-conditioned cab or a fit-out team working indoors. A rigid temperature limit would struggle to reflect those differences.

Yet there is also a growing argument that the current system places too much emphasis on judgment and not enough on clear standards.

Climate scientists predict that extreme heat events will become more common in the UK. Temperatures that once occurred once every decade are becoming regular summer occurrences. Construction workers, many of whom spend long periods outdoors performing physically demanding tasks, are among those most exposed.

The industry has become accustomed to planning for cold weather. Winter working procedures are well established. Yet many sites still treat extreme heat as an inconvenience rather than a significant health risk.

Heat exhaustion, dehydration and heat stroke are not minor issues. They affect concentration, decision-making and physical performance. In an industry where safety often depends on workers remaining alert and focused, that should concern every contractor and client.

Perhaps the debate should move beyond whether a single legal maximum temperature is desirable.

A more practical approach might be to establish clearer trigger points that require employers to introduce specific controls. These could include mandatory rest breaks, enhanced welfare facilities, adjusted working hours or restrictions on certain high-intensity tasks once temperatures reach predetermined levels.

Such measures would preserve the flexibility of the current risk-based system while providing greater consistency across the industry.

Importantly, employers should also recognise that heat does not affect everyone equally. Workers with underlying health conditions, pregnant employees and young workers may be particularly vulnerable. Under the Equality Act 2010, some employees may be entitled to reasonable adjustments, while health and safety regulations already require employers to consider those at greater risk.

For workers, there is no automatic right to refuse to attend work during a heatwave. However, where someone reasonably believes they face serious and imminent danger, legal protections may apply. This underlines the importance of robust risk assessments and open communication between management and the workforce.

The most effective response to heat is unlikely to come from sunscreen and water bottles alone. The hierarchy of control reminds us that personal protective equipment should be the last line of defence, not the first. Better planning, engineering controls, shaded work areas, revised schedules and mechanisation of physically demanding tasks are often far more effective.

The question facing construction is not simply whether there should be a maximum working temperature. It is whether the industry’s existing approach is evolving quickly enough to keep pace with a changing climate.

As heatwaves become more frequent, clients, contractors and regulators may soon find that what once seemed an occasional challenge has become a permanent feature of project delivery. Whether through legislation or stronger guidance, the pressure to define what constitutes safe working in extreme heat is only likely to grow.

The construction sector has spent decades learning how to manage cold-weather risks. It may now need to show the same level of seriousness about the dangers of working in the heat.

Adam Annetts is director of technical services at SMAS Worksafe