This is an extract of our concise Risk Assessment for working in high heat:-

Legislative and Guidance Framework

This assessment has been prepared with reference to the following UK legislation, Approved Codes of Practice (ACOPs), and industry guidance applicable to construction:

• Health and Safety at Work etc. Act 1974 (HSWA) — section 2 places a general duty on employers to ensure, so far as is reasonably practicable, the health, safety and welfare of employees, including site operatives and subcontractors.
• Construction (Design and Management) Regulations 2015 (CDM 2015) — requires principal contractors and contractors to plan, manage and monitor construction work to ensure it is carried out without risk to health and safety, and to maintain welfare facilities under Schedule 2.
• Management of Health and Safety at Work Regulations 1999 — requires suitable and sufficient risk assessment and implementation of preventive and protective measures.
• Workplace (Health, Safety and Welfare) Regulations 1992, Regulation 7 and ACOP — temperature in indoor workplaces (welfare cabins, site offices) must be “reasonable”. Note: these Regulations do not apply to most open-air construction operations, but the principle of providing reasonable working conditions is reflected through CDM 2015 welfare provisions.
• CDM 2015, Schedule 2 — welfare facilities requirements, including provision of drinking water, rest facilities, and shelter from adverse weather conditions on site.
• Control of Substances Hazardous to Health Regulations 2002 (COSHH) — relevant where heat increases volatility of substances (e.g. solvents, bituminous products) or where PPE/RPE use in heat increases physiological strain.
• Personal Protective Equipment at Work Regulations 1992 — relevant to selection of PPE that balances protection with heat strain, particularly high-visibility clothing and head protection.
• HSE Guidance — “Temperature in the workplace”, “Heat stress”, and HSE construction-specific guidance on working in hot weather (no statutory maximum working temperature exists in UK law for outdoor work; the duty is risk-based).
• Working Time Regulations 1998 — entitlement to rest breaks, relevant to break scheduling during periods of high heat.
• HSE Thermal Comfort Checklist and WBGT (Wet Bulb Globe Temperature) methodology — used as supporting assessment tools for heat stress evaluation on site.

Note: There is no legal maximum working temperature in the UK, indoors or outdoors. The duty on principal contractors and employers is to assess and manage heat-related risk so far as is reasonably practicable, with particular regard to the unique exposure of construction operatives to direct sun, radiant heat from materials/plant, and physically demanding manual work.

Hazard Identification — Construction-Specific

• Heat stress / heat exhaustion from prolonged exposure to direct sun and high ambient temperature during manual labour (groundworks, block/brick laying, concreting).
• Heat stroke — severe, potentially life-threatening progression, particularly amongst operatives working at height or in confined/enclosed spaces (plant rooms, ducts, roof voids).
• Dehydration from sustained physical exertion, often compounded by limited access to welfare facilities on larger or remote sites.
• Radiant heat from materials and surfaces — roofing materials, scaffold tube, steelwork, tarmac/asphalt, and plant/machinery can significantly exceed ambient air temperature.
• Heat combined with mandatory PPE — hard hats, high-visibility clothing, harnesses, and RPE (e.g. for cutting/grinding tasks) restrict heat dissipation and increase core body temperature.
• Loss of concentration and slower reaction times increasing risk of falls from height, contact with moving plant, and manual handling injuries.
• Sunburn and long-term UV exposure risk (skin cancer) for operatives working outdoors for extended periods, particularly those with reduced shirt/clothing coverage.
• Increased risk to operatives working in confined spaces, roof spaces, or plant rooms where ventilation is poor and temperatures can exceed external ambient levels significantly.
• Dust and dehydration interaction — hot, dry conditions on groundworks/demolition sites increasing both dust exposure and dehydration risk.
• Pre-existing medical conditions — cardiovascular, respiratory, renal conditions, certain medications, and reduced fitness/acclimatisation in seasonal or agency labour.

Who Might Be Harmed

• Operatives undertaking groundworks, bricklaying/block laying, concreting, and general labouring.
• Roofers and those working at height with prolonged direct sun exposure and radiant heat from roofing materials.
• Scaffolders and steel erectors working with metal materials that retain significant heat.
• Plant and machinery operators in cabs without effective climate control.
• Operatives wearing mandatory PPE/RPE (hard hats, hi-vis, harnesses, respiratory protection).
• Lone workers and those on remote or temporary sites with limited welfare facility access.
• New starters, agency workers, and seasonal labour not yet acclimatised to heat or site conditions.
• Vulnerable individuals — pregnant workers, older workers, those with underlying health conditions or on relevant medication.

Site visitors, supervisors, and members of the public adjacent to the site boundary.

The full 6 page Risk Assessment is available HERE