Construction sites carry a fire risk profile unlike any other workplace environment. Layouts change daily, fire compartmentation does not yet exist, multiple contractors share the same space, and fire-intensive activities such as hot work and temporary electrical installations sit alongside large quantities of combustible material. This guide brings together the latest construction-related fire data from the Ministry of Housing, Communities & Local Government (MHCLG), the Health and Safety Executive (HSE) and the Fire Industry Association (FIA), and sets out the legal duties that principal contractors and employers must meet.
Key facts and figures
- ~25% of all UK workplace fires in 2024/25 occurred in industrial premises.
- 180+ workplace fires in 2024/25 were caused by hot work — welding, cutting, grinding and brazing.
- £657,074 is the average loss from a major business fire, per FIA data.
- ~6% of the UK workforce works in construction, yet the sector accounts for a disproportionately high share of workplace fatalities.
- 58% of fire safety audits nationally were judged satisfactory in 2024/25.
Construction site fire risk: dynamic, dangerous and demanding
Construction sites carry a fire risk profile unlike any other workplace environment. They are dynamic — the layout changes daily as the build progresses, and the passive fire protection and compartmentation that would contain a fire in a finished building does not yet exist. They are diverse, with multiple employers and contractors sharing the same space, often without a single shared understanding of the risks present on any given day.
They are also inherently fire-intensive. Hot work, temporary electrical systems and large volumes of combustible material — timber framing, packaging, insulation and solvents — are routinely stored close to potential ignition sources. The result is an environment where a single uncontrolled spark can spread rapidly through an unprotected structure.
Construction site fire causes
Construction fires tend to stem from a recurring set of causes, most of which are preventable with the right controls and a trained fire marshal on site:
- Arson — the leading cause of fire on vacant or partially occupied sites. Timber frameworks and packaging materials are readily combustible and make sites an attractive target.
- Hot work — welding, cutting, grinding and brazing generate sparks that can travel considerable distances and smoulder unnoticed. Hot work caused over 180 workplace fires in 2024/25.
- Temporary electrical installations — generators, temporary distribution boards and site cabins degrade rapidly in the harsh site environment.
- Flammable materials storage — timber, solvents, adhesives, insulation and fuel can accumulate and provide ample fuel for ignition.
- Smoking — despite site restrictions, smoking remains a persistent cause of accidental fires.
Legal requirements for construction site fire safety
Four regulatory frameworks govern fire safety on construction sites, and principal contractors and employers must satisfy all of them:
- The Regulatory Reform (Fire Safety) Order 2005 — principal contractors must conduct a fire risk assessment for the site.
- The Construction (Design and Management) Regulations 2015 — require fire safety to be embedded within the Construction Phase Plan.
- The Electricity at Work Regulations 1989 — govern the safety of temporary electrical installations.
- Hot Work Permit Systems — a necessary control requiring formal authorisation and documented precautions before any hot work begins.
The CDM fire safety obligation
Under CDM 2015, the Construction Phase Plan is the central document for managing fire safety throughout the build. It must identify the significant fire hazards on site and set out the control measures, together with the arrangements for fire detection and alarm, evacuation procedures, firefighting provisions and the methods for contacting the fire and rescue service.
Critically, the plan must also assign clear fire safety roles, including named fire marshals responsible for prevention, raising the alarm and assisting with evacuation. Appointing and training those competent persons is a legal expectation, not an optional extra.
Arson on construction sites
Construction sites are among the most targeted property types for deliberate fire-setting. The combination of combustible materials, limited out-of-hours occupation and easy access makes them attractive to arsonists, and the financial consequences of a deliberate fire can be severe — the average major business fire loss stands at £657,074.
Effective preventive measures include robust perimeter security, out-of-hours surveillance, removal or secure storage of combustible materials, CCTV monitoring and active liaison with the local fire and police services. Treating arson as a foreseeable risk — rather than an act of misfortune — is central to a defensible fire risk assessment.
| Measure (UK, 2024/25) | Figure |
|---|---|
| Share of workplace fires in industrial premises | ~25% |
| Workplace fires caused by hot work | 180+ |
| Average major business fire loss | £657,074 |
| Construction share of UK workforce | ~6% |
| Fire safety audits judged satisfactory | 58% |
Sources & references
- Ministry of Housing, Communities & Local Government (MHCLG) — Detailed Analysis of Fires (April 2024 to March 2025) — Gov.uk
- Ministry of Housing, Communities & Local Government (MHCLG) — Primary Fires on Construction Sites (Ad-Hoc Statistics) — Gov.uk
- Health and Safety Executive (HSE) — Construction (Design and Management) Regulations 2015 — HSE
- Fire Industry Association (FIA) — Fires and Their Economic Toll on UK Businesses — FIA
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Mark writes about workplace fire safety, compliance and accredited training for Fire Marshal Training, part of Online CPD Academy.