Construction Site Fire Risk Assessments

A construction site is the hardest kind of premises to assess, for one structural reason: everything the assessment depends on is temporary. Escape routes move as the build progresses. Compartmentation is usually installed late, so the building spends months without the protection its design assumes. Fire load arrives in pallets and accumulates as packaging. And the ignition sources are not incidental — cutting, welding and grinding are the work.

On top of that, two regimes can apply at once, and which duties bite depends on whether anyone is still occupying the building.

This article summarises UK fire safety law and guidance for educational purposes and is not legal advice. Duty-holders carry the legal liability for fire safety on site. For specific compliance questions, consult a competent fire risk assessor or your local fire and rescue authority.

Two Regimes, and How to Tell Which Applies

This is the part that gets conflated, so it is worth separating carefully.

CDM 2015 is law. The Construction (Design and Management) Regulations 2015 govern construction work as an activity. Three regulations carry the fire-specific duties.

Regulation 30 — Emergency procedures:

"suitable and sufficient arrangements for dealing with any foreseeable emergency must be made and, where necessary, implemented"

including evacuation procedures, taking account of the type of site, its size, the number of people on it, the work equipment and the hazardous materials present — and requiring that affected people understand the arrangements and that they are tested periodically.

Regulation 31 covers emergency routes and exits. Regulation 32 — Fire detection and fire-fighting:

"suitable and sufficient fire-fighting equipment and fire detection and alarm systems must be provided and located in suitable places"

with equipment examined, tested at suitable intervals and properly maintained, non-automatic equipment easily accessible and indicated by suitable signs, workers instructed in the correct use of equipment they may need to use, and high-fire-risk activities restricted to suitably instructed people.

HSG168 is guidance, not law. Fire safety in construction (HSG168, third edition 2022) says so on its own imprint page:

"This guidance is issued by the Health and Safety Executive. Following the guidance is not compulsory, unless specifically stated, and you are free to take other action. But if you do follow the guidance you will normally be doing enough to comply with the law. Health and safety inspectors seek to secure compliance with the law and may refer to this guidance."

Treating HSG168 as if it were regulation overstates the position; ignoring it because it is "only guidance" understates it. It is the benchmark against which an inspector or an insurer will read a site's arrangements.

The Fire Safety Order may also apply — and often does. HSG168 records that the Fire Safety Order "applies in England and Wales", and at paragraph 21 records that where the responsible person implements preventive and protective measures they must do so on the basis of the principles in Part 3 of Schedule 1 to the Order.

The practical test is whether there are premises in use. A greenfield site with nothing occupied sits principally under CDM. But refurbishment of an occupied office, works to a block of flats with residents still living there, a fit-out in a shop trading through it — in all of those, the premises remain premises, the responsible person under Article 3 still holds their duty, and the Article 9 assessment has to account for the works rather than be suspended for their duration.

That overlap is where liability tends to be argued after the event: the principal contractor assumed the building's responsible person was covering the occupied part, the responsible person assumed the contractor's site plan covered everything, and the interface between them was nobody's.

What the Assessment Has to Cover

The structure is the familiar one — identify hazards, identify who is at risk, evaluate, act, record, review — but three inputs behave differently on a construction site.

Sources of ignition are the work itself

Hot work is not a peripheral hazard here. HSG168's recommended controls are specific and worth following closely:

• Substitute where reasonably practicable. The guidance suggests substituting hot works processes with cold systems where reasonably practicable — for example, roof systems that avoid naked flames.
• Designate an area. Conduct routine hot works such as steel cutting in a designated area away from combustible material and the main structure, and consider fire-resisting enclosures for hot work processes.
• Permit to work. Strictly control hot processes and hot work by operating permit-to-work schemes.
• Fire watch, including breaks. Maintain a careful watch for fire while hot work is being carried out, and during breaks in the working day.
• And after. A continuous fire watch of the hot work area for at least an hour after the end of hot work, followed by at least one more check two hours after.

That last one is the detail most site plans miss. The fire that starts from hot work frequently does not start during it.

The guidance also addresses the everyday sources: no smoking on site except in designated areas away from buildings and combustible materials, no bonfires, and gas cylinders stored outdoors in a secure cage.

Fire load arrives and accumulates

Packaging, offcuts and waste build up during the day and are at their worst at the end of it. HSG168 recommends developing a formal system for the control of combustible waste, ensuring waste materials and rubbish are not allowed to build up and are carefully stored until properly disposed of — particularly at the end of the day, for example in lockable metal skips.

Arson is a real part of the picture on construction sites, which is why waste control, site security and lighting sit alongside the fire precautions rather than separately from them.

Escape routes are provisional

The route that worked last month may now run through an area that is being opened up. Temporary escape routes need the same scrutiny as permanent ones: distance, width, obstruction, lighting, signage and a final exit that opens. Reg 31 makes this a duty; the assessment is where the current arrangement gets recorded.

Compartmentation deserves particular attention because it usually arrives late. A building under construction may have its final layout without any of its final fire resistance, and an assessment that reads the drawings rather than the site will describe protection that does not yet exist.

Sleeping accommodation on site

HSG168 carries a dedicated appendix on sleeping accommodation — both within the building being constructed and in proprietary designed accommodation. If anyone sleeps on the site, the assessment changes character entirely: the detection standard, the escape strategy and the alarm arrangements all have to work for someone asleep, which is the same principle that drives the assessment in HMOs and care homes.

Reviewing It

A fixed-premises assessment can sit for twelve months. A construction site's cannot, because the premises change under it.

Tie the review to the build rather than to the calendar: at each significant phase change, when escape routes are altered, when compartmentation is installed or breached, when a new high-risk process starts on site, and when the occupied/unoccupied boundary moves. The Article 9(3) duty to review where there is reason to suspect the assessment is no longer valid or there has been a significant change fits construction almost too neatly — on an active site, the significant change is continuous.

The free FRA review date calculator will set a baseline interval, and the 30-point fire risk assessment checklist covers the on-site ground that carries across. For pricing a construction-phase instruction, which is typically re-visited more often than a one-off survey, the free FRA cost calculator estimates by building type and complexity.

Summary

Construction fire risk assessment sits across two regimes. CDM 2015 is the binding instrument for the construction activity — regulation 30 for emergency procedures, 31 for escape routes and exits, 32 for detection and fire-fighting. HSG168 (third edition, 2022) is HSE guidance, expressly not compulsory, but it is the standard an inspector will read the site against. And where the works are in or attached to premises still in use, the Fire Safety Order continues to apply and the responsible person's duty does not pause.

The three things that make the assessment different from a fixed-premises one are that ignition is the work, that fire load accumulates daily, and that escape routes and compartmentation are provisional. Control hot work by permit with a fire watch that continues an hour past the end of the job and is checked again two hours after, control waste to a formal system, and re-assess at phase changes rather than annually.

AssessKit doesn't do construction-phase assessments. Where the works are inside a building that's still in use, though, that building's own fire risk assessment still stands and needs reviewing as the works change it. That part is what AssessKit is for: it supports PAS 79-1 for non-domestic premises and BS 9792 for housing, and keeps each site's findings, actions and next review date in one place. Start free — the Free plan covers two assessments a month, no card required. See pricing or read about who is building it.

Sources

• The Construction (Design and Management) Regulations 2015 — SI 2015/51 (legislation.gov.uk)
• CDM 2015, regulation 30 — Emergency procedures (legislation.gov.uk)
• CDM 2015, regulation 31 — Emergency routes and exits (legislation.gov.uk)
• CDM 2015, regulation 32 — Fire detection and fire-fighting (legislation.gov.uk)
• Fire safety in construction, HSG168 third edition 2022 (HSE)
• Regulatory Reform (Fire Safety) Order 2005, Article 3 — Meaning of "responsible person" (legislation.gov.uk)
• Regulatory Reform (Fire Safety) Order 2005, Schedule 1 (legislation.gov.uk)