A heatwave does not arrive on a construction site as a weather event. It arrives as a duty holder responsibility.
Under the Construction (Design and Management) Regulations 2015 (CDM 2015), principal contractors must plan, manage, monitor and coordinate health and safety across the construction phase. That responsibility does not pause in hot weather – it intensifies.
On multi-contractor sites during peak summer, where workers from multiple trades operate in direct sun exposure, heat risk becomes more complex and more critical to manage.
For public sector clients and procurement teams, expectations are also evolving. Following Procurement Policy Note (PPN) 03/24, the Common Assessment Standard (CAS) is now the preferred pre-qualification route for many construction projects above the threshold. This means health and safety capability – including how contractors manage environmental risks such as heat – is subject to structured scrutiny.
This guide explains:
- What CDM 2015 requires in hot weather
- What a compliant construction phase plan should include
- What “good” heat safety management looks like to procurement teams and HSE inspectors
What should be in a construction phase plan for hot weather?
Under CDM 2015, the construction phase plan must be prepared before work starts and regularly reviewed to remain fit for purpose.
Heat is a foreseeable seasonal hazard. A plan that has not been updated for summer conditions may not meet compliance expectations.
A robust construction site heat safety plan should include:
Site-specific cheat risk assessment
- Reflects project type, environment and exposure
- Considers trade-specific risks (e.g. roofing vs groundworks)
- Accounts for PPE requirements and workload intensity
Defined roles and responsibilities
- Named individuals responsible for monitoring temperatures
- Clear authority for modifying work (e.g. rescheduling or stopping tasks)
- Assigned responsibility for worker welfare checks
Welfare provision (CDM-compliant)
- Readily available cool drinking water
- Shaded rest areas
- Heat-aware first aid arrangements
- Scheduled breaks for cooling down
Communication processes
- Clear method for communicating changes across all contractors
- Daily briefings during high heat periods
- Documented toolbox talks
Trigger points and decision protocols
- Defined thresholds (e.g. temperature or Met Office alerts
- Pre-agreed actions (adjust hours, extend breaks, pause work)
- Escalation pathways
The multi-contractor site challenge
Managing heat risk becomes significantly more complex on multi-contractor sites.
Under CDM 2015, principal contractors must ensure all appointed contractors have the skills, knowledge, experience and organisational capability to work safely.
In hot weather, that includes confidence that subcontractors can manage heat risk effectively.
Effective coordination requires:
- Pre-appointment due diligence on environmental risk management
- Site inductions that include heat safety
- Shared welfare facilities accessible to all workers
- Clear escalation routes for raising concerns
- Ongoing review of heat control measures during prolonged hot periods
Public sector procurement: What contracting authorities expect
PPN 03/24 has strengthened expectations around contractor competence.
The Common Assessment Standard provides a consistent baseline for evaluating health and safety systems.
While heat may not always be assessed explicitly, procurement teams are effectively assessing whether contractors can:
- Identify foreseeable risks
- Implement practical control measures
- Maintain safe working conditions under changing environments
The key question is not simply:
“Does this contractor hold certification?”
It is:
“Are their management systems robust enough to manage real-world risks, including heat?”
CHAS assessment focuses on evidence-based capability, not self-declaration. It evaluates whether systems are credible, implemented and aligned with legislative requirements.
HSE inspection readiness in hot weather
Construction remains a high-enforcement sector.
During a heatwave, HSE inspectors are likely to examine:
Construction phase plan
- Includes heat as a recognised hazard
- Updated to reflect current conditions
Worker briefing evidence
- Toolbox talks
- Induction records
- Supervisor logs
Functional welfare facilities
- Accessible shade
- Cool (not warm) drinking water
- Maintained and in use
Identification of vulnerable workers
- New starters
- Workers in heavy PPE
- Individuals with health considerations
Incident and near-miss records
- Documented heat-related cases
- Evidence of response and review
If documentation is missing, it cannot be recreated retrospectively. This creates significant exposure in the event of enforcement action.
How CHAS certification supports heat safety management
CHAS has been assessing contractor health and safety management since 1997 and is recognised by over 1,000 public and private sector organisations.
CHAS certification supports heat safety management by ensuring:
Robust risk management systems
Contractors must demonstrate credible processes for identifying and managing workplace hazards, including environmental risks.
Verified pre-qualification capability
For principal contractors and buyers, CHAS provides a trusted, independently assessed baseline of compliance capability.
This reduces reliance on self-reported evidence and strengthens procurement decisions.
The standard that stands up under scrutiny
The true test of a health and safety system is not routine conditions – it is how it performs under pressure.
A heatwave is exactly that test.
The organisations that manage it well are those that:
- Plan in advance
- Document clearly
- Implement consistently
- Review continuously
That is the standard increasingly expected across construction and procurement. And it is the standard CHAS assessment is designed to validate.
To understand how CHAS certification strengthens your compliance and pre-qualification position, visit CHAS or speak to our team.
