Fire Safety · Mandatory · Construction

Hot Works Permit — Fire

A fire-focused permit for hot works activities addressing fire prevention controls.

Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. RRO 2005 / MHSWR remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.

Legal basis	Regulatory Reform (Fire Safety) Order 2005 (RRO) — fire precautions / Management of Health and Safety at Work Regulations 1999 (MHSWR) — risk assessment and control
Hot works defined	Any operation involving open flames, sparks, or heat that could ignite surrounding materials — including welding, cutting, grinding, brazing, soldering, torch-applied roofing, bitumen boilers, and use of heat guns
Spark travel	Sparks and hot particles from grinding and cutting operations can travel up to 10 metres from the work location and can ignite combustible materials at that distance
Smouldering risk	Hot works can cause smouldering fires that do not become visible for hours after the work has finished — fires have started overnight after hot works carried out during the day
Insurance condition	Most construction insurance policies require a formal hot works permit system as a condition of cover — failure to operate a permit system may void the policy
Permit requirement	Each hot works permit must be operation-specific and time-limited — blanket authorisations are not acceptable

1. Hot Works Permit

Hot works are the single most common cause of fires on construction sites. The hot works permit is the primary control measure for managing the fire risk associated with welding, cutting, grinding, brazing, soldering, torch-applied roofing, and any other operation that produces open flames, sparks, or sufficient heat to ignite surrounding materials. A formal permit-to-work system ensures that every hot works operation is individually assessed, that appropriate precautions are in place before work begins, and that post-work fire watch and inspection procedures are followed.

Sparks and hot particles generated by grinding and cutting can travel up to 10 metres from the point of work. They can pass through gaps in floors, walls, and partitions, and can ignite combustible materials that are not visible to the operative. Smouldering fires caused by hot works may not become apparent for hours after the work has finished — construction site fires have started overnight, long after the operatives have left, because a spark lodged in insulation, timber, or packaging material and smouldered until it eventually ignited. This is why the post-work fire watch is so critical.

Most construction insurance policies require a formal hot works permit system as a condition of cover. Failure to operate a permit system, or failure to follow the permit procedures, may void the insurance policy entirely. This means that if a fire occurs as a result of hot works carried out without a valid permit, the insurer may refuse to pay the claim. The permit must be operation-specific (issued for a particular task, in a particular location, for a defined duration) and time-limited. Blanket authorisations that cover multiple operations, locations, or days are not acceptable.

60-minute minimum post-work fire watch

After hot works are completed, a dedicated fire watch must be maintained for a minimum of 60 minutes. The fire watch person must remain in the area, must have a suitable fire extinguisher immediately available, and must check the work area and all adjacent areas (including floors above and below, and the other side of walls and partitions) for signs of fire, smoke, or smouldering. The 60-minute minimum is an industry standard and an insurance requirement — some insurers and site-specific rules require longer fire watch periods. The fire watch must not be combined with other duties during the watch period.

2. Content

A compliant hot works permit must document the specific operation, the precautions in place, and the post-work fire watch arrangements. The following table sets out the required content for a hot works permit.

Item	Detail
Permit reference number	Unique sequential reference number for tracking and audit purposes — permits must be numbered and logged
Location	Precise location of the hot works operation — building, floor, room, grid reference, or marked on a site plan. The location must be specific enough that the fire watch person and any emergency responder can identify exactly where the work is being carried out
Description of works	Clear description of the hot works operation to be carried out — type of work (welding, cutting, grinding, brazing, torch-applied roofing), materials involved, and equipment to be used
Duration	Start time and finish time for the hot works operation — the permit is valid only for the specified duration and expires at the stated finish time. A new permit is required for any extension
Operative	Name of the person carrying out the hot works, their employer, and confirmation that they are competent and trained in the fire risks associated with hot works
Pre-work checks	Checklist of pre-work fire precautions: combustible materials removed or protected within 10 metres, gaps in floors/walls/partitions sealed, fire detection system notified, fire extinguisher in place, fire blankets available, flammable atmospheres tested and clear
Authorised by	Name and signature of the person authorising the hot works — this must be a person with authority to issue permits (typically the site manager, fire safety advisor, or designated permit issuer)
Fire watch during works	Name of the person maintaining fire watch during the hot works operation, confirmation that they have a fire extinguisher, and confirmation that they are not the same person carrying out the hot works (unless the risk assessment specifically permits it for low-risk operations)
Post-work fire watch	Name of the person maintaining fire watch after the hot works are completed, start time and end time of the fire watch period (minimum 60 minutes), confirmation of fire extinguisher provision, and record of checks carried out during the watch period
End-of-day inspection	Confirmation that a final inspection of the hot works area and all adjacent areas has been carried out at the end of the working day, with the name of the person carrying out the inspection and the time it was completed
Permit closure	Confirmation that the hot works have been completed, the fire watch period has been completed satisfactorily, the end-of-day inspection has been carried out, and the permit is closed — signed and dated by the permit issuer or their delegate

3. Common Mistakes

Blanket authorisation instead of operation-specific permits

A hot works permit must be issued for a specific operation, in a specific location, for a defined duration. Blanket authorisations that cover an entire day, multiple locations, or multiple operatives defeat the purpose of the permit system. Each permit must require the authorising person to assess the specific conditions at the specific location before the work begins. A blanket permit means that no one has checked whether combustible materials have been removed, whether gaps in floors and walls have been sealed, whether the fire detection system has been notified, or whether a fire extinguisher is in place. Insurance policies that require a hot works permit system will not accept blanket authorisations.

Post-work fire watch of less than 60 minutes

The industry standard minimum for a post-work fire watch is 60 minutes after the completion of hot works. This is because sparks and hot particles can lodge in combustible materials and smoulder for a considerable time before igniting. A fire watch of 15 or 30 minutes is not sufficient — fires have started well beyond the 30-minute mark. The fire watch person must remain in the area for the full duration, must have a fire extinguisher immediately available, and must check the work area and all adjacent areas (including above, below, and on the other side of walls and partitions). Some insurers and some sites require fire watch periods longer than 60 minutes — the permit must specify the required duration.

No end-of-day inspection

Even with a post-work fire watch, a further inspection of the hot works area must be carried out at the end of the working day before the site is secured for the night. This is because smouldering fires can take hours to develop. If hot works were carried out in the morning and the fire watch was completed by lunchtime, a fire could still start in the evening or overnight. The end-of-day inspection is the final check to ensure that no smouldering has occurred. It must cover the work area and all adjacent areas, and must be documented on the permit. Failure to carry out an end-of-day inspection is a common contributing factor in overnight construction site fires.

4. Frequently Asked Questions

What is a fire watch and who can conduct it?▾

A fire watch is the continuous monitoring of a hot works area during and after hot works operations for the purpose of detecting and extinguishing any fire that may result from the work. The fire watch person must remain in the area for the entire duration of the watch, must have at least one suitable fire extinguisher immediately to hand, and must check the work area and all adjacent and connected spaces (including floors above and below, voids, cavities, and the other side of walls and partitions) for any signs of fire, smoke, heat, or smouldering. The fire watch person must be a competent person who has received training in the use of fire extinguishers and understands the fire risks associated with hot works. They must know the site emergency procedures and how to raise the alarm. During the fire watch period, the fire watch person must not be assigned any other duties — their sole task is to monitor for fire. Any worker who has received appropriate training can act as the fire watch person, but they must not be distracted by other tasks during the watch period.

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