How to Manage Contractor Hot Works
Most fires caused by hot works begin with a routine job. A contractor is on the roof replacing a section of membrane, cutting out an old bracket or welding a new pipe support, and the work goes to plan until a spark or a piece of hot slag lands somewhere nobody checked. Hours later, after the contractor has packed up and left, a smouldering fire in a roof void or a pile of packaging finally takes hold.
Hot works are one of the most common causes of serious fires in commercial and industrial buildings in the UK, and most of those fires are preventable. The controls are well established and need no expensive equipment. What they do need is a responsible person who treats contractor work as a change to the building's fire risk, and a permit system that is followed on the day as well as on paper.
In this article we explain what counts as hot works, where the legal duties sit, and how to manage contractors safely from the first conversation to the final sign-off. We also return to a fire much closer to home, at Roberts Bakery in Northwich, which shows how much is at stake when construction work takes place on an occupied site.
What counts as hot works?
Hot works are any work that uses or produces heat, flame or sparks capable of igniting materials nearby. Welding and flame cutting are the obvious examples, but the category is much wider than most people expect. It includes angle grinding, brazing and soldering, torch-applied roofing felt, hot air guns used to strip paint or seal membranes, and thawing frozen pipes with a blowtorch.
The danger is rarely confined to the spot where the work is happening. Sparks from a grinder can travel several metres and drop through gaps in floors, into wall cavities and behind cladding. Heat also travels along steel beams and pipework, so a weld on one side of a wall can ignite insulation or stored goods on the other side. Hot slag can sit in dust or debris for a long time before it produces visible smoke, which is why so many hot work fires are discovered after the workers have gone home.
Who is responsible when a contractor is on site?
In England and Wales, the Regulatory Reform (Fire Safety) Order 2005 places duties on the responsible person for the premises, usually the employer or whoever has control of the building. Bringing in a contractor does not transfer those duties. The responsible person still has to make sure the fire risk assessment reflects what is happening in the building, including temporary work that introduces new ignition sources.
The Order also expects co-operation where more than one party has duties in the same premises. Article 22 requires responsible persons who share premises to co-operate and coordinate their fire safety measures, and Article 20 requires contractors working on site to be given information about the risks and the precautions in place. In practice, the site should explain its alarm system, escape routes, assembly point and any restricted areas before work starts, and the contractor should explain exactly what their work involves.
Where the work counts as construction work, the Construction (Design and Management) Regulations 2015 also apply, and they include a specific duty to prevent fire on construction sites. Scotland has equivalent requirements under the Fire (Scotland) Act 2005. The detail varies, but the principle is the same across the UK, which is that hot works need to be planned, authorised and supervised by someone with the authority to stop them.
Case study: the Roberts Bakery fire, Northwich
On 5 June 2023, fire broke out at Roberts Bakery on Gadbrook Park in Northwich. Cheshire Fire and Rescue Service described a well-developed fire in a temporary roof structure, involving a ceiling joist and scaffolding boards, which spread into the production area below. Twelve fire engines attended, and all staff and contractors were evacuated safely.
We covered the incident and its aftermath in detail in our earlier article, The Roberts Bakery Northwich Fire: Fire in a Temporary Roof Structure. The official cause has not been published, so we are careful not to say that hot works started this fire. What the published details do show is a fire that began in materials associated with roof works on a building that remained in production, which is exactly the situation where contractor activity needs the closest control.
The consequences went far beyond the building. The fire put two-thirds of the company's production out of action for more than a year, and many customers who found other suppliers during the rebuild did not return. In October 2025 the 138-year-old family business entered administration, and it was sold in a pre-pack deal that saved around 433 jobs.
Why this matters for every site: Roberts had insurance, other production sites and the scale to attempt a recovery. A smaller, single-site business facing a fire of this size would have far fewer options. Good control of contractor work is one of the most effective ways to make sure that situation never arises.
Before the work starts
The first question is whether hot work is needed at all. Many jobs can be done with cold methods, such as bolted connections in place of welds, mechanical pipe cutters in place of disc cutters, or cold-applied roofing systems in place of torch-on felt. Where an item can be removed and worked on in a workshop, that is almost always safer than working on it in place.
Where hot work cannot be avoided, the responsible person should review the fire risk assessment before the contractor arrives. The review should consider what is above, below and on the other side of the work area, whether there are hidden combustibles such as insulated panels or roof voids, and whether the work will affect fire detection, sprinklers or escape routes.
Choosing the contractor matters just as much. Ask for a method statement and risk assessment that describe the hot work specifically, and check that the operatives are trained and experienced in the process they will use. Many insurers and clients now expect hot work operatives to hold a recognised qualification, such as the Fire Protection Association's Hot Work Passport. It is also worth confirming that the contractor's own insurance covers hot work, since some policies exclude it or attach conditions.
The hot work permit
A hot work permit is a written authorisation that links a specific task to a specific place and time, with the precautions confirmed before work begins. It is the central control for contractor hot works, and most commercial insurance policies require one. A good permit records:
- the exact location and nature of the work, and the equipment being used
- the start and expiry time, normally within a single shift
- the precautions checked by the person issuing the permit
- the name of the person providing the fire watch
- the fire watch times and the final sign-off
The permit should be issued by a competent person on the site's side, someone who knows the building and has the authority to refuse or stop the work. When contractors write and sign their own permits and nobody from the site checks the area, the permit becomes paperwork and stops working as a control. A separate permit should be issued for each job and each area, so a permit for welding on the ground floor cannot be stretched to cover cutting work on the roof later the same afternoon.
Preparing the work area
Preparation is where most hot work fires are prevented. Combustible materials should be moved well away from the work, commonly at least ten metres, and anything that cannot be moved should be covered with fire-resistant blankets. Gaps in floors and walls should be sealed, and the area below the work should be checked and protected, because sparks and hot debris fall and can land on stored goods or packaging.
Suitable fire extinguishers should be at the work position, and both the operatives and the fire watch should know how to use them. If fire detection has to be isolated to prevent false alarms, only the affected zone should be isolated, for the shortest possible time, with a named person responsible for reinstating it. Sprinkler systems should stay in service throughout. Everyone involved should know how to raise the alarm and where the nearest call point is.
Sites that handle flammable dusts, solvents or gases need extra care, and this includes food production, woodworking and printing. Flour and other fine dusts settle on high surfaces such as beams and ducting, where sparks can ignite them, so cleaning and, where needed, atmosphere testing should form part of the permit checks.
Fire watch and sign-off
The fire watch is the part of the system most often cut short. The person on fire watch observes the work area and its surroundings during the work and afterwards, ready to raise the alarm and tackle a small fire. They should be someone other than the person doing the hot work, whose attention will be on the task.
Guidance from RISCAuthority, published by the Fire Protection Association, recommends a continuous fire watch for at least 60 minutes after work finishes, followed by checks at intervals of no more than 20 minutes until two hours have passed. The fire risk assessment may call for longer periods, for example where work has taken place near roof voids or insulated panels. This has a practical consequence for scheduling. Hot work should finish early enough in the day for the full fire watch to be completed while the site is still staffed.
The permit should only be closed once the fire watch is complete and the area has been checked, including the spaces above, below and on either side of the work.
Temporary structures, scaffolding and roof works
Roof refurbishment on an occupied building brings its own risks, as the Northwich fire showed. Scaffolding boards, timber decking, protective sheeting and stored roofing materials add combustible material to the outside and top of a building, often in places that fire detection does not cover. Roof voids, built-up roofs and insulated panels can also allow fire to spread out of sight before anyone notices.
Where roof works are planned, the responsible person and the contractor should agree how materials will be stored, how much will be kept on the roof at any one time, how the area will be checked at the end of each day, and how the fire service would gain access if needed. Torch-on roofing should be treated as hot work in every case, and the fire watch should include the underside of the roof deck wherever that can be reached.
Making it routine
For most sites, hot works happen regularly. Maintenance contractors return again and again, and familiarity can lead to shortcuts. The most reliable sites treat the permit system as a normal part of how contractors work, review completed permits from time to time to check the fire watch was carried out properly, and make sure their own staff understand the procedure through fire safety training. The fire risk assessment should refer to the hot work procedure, and it should be reviewed whenever significant building work is planned.
For warehouse and industrial premises, where fuel loads are high and buildings are large, a hot work fire can mean lost production, lost customers and, as Roberts Bakery found, a threat to the future of the business itself. Our article on what causes warehouse fires covers the wider picture.
Planning building work or maintenance on site?
We can review your fire risk assessment before contractors arrive, help you put a practical hot work procedure in place, and train your staff to manage permits with confidence. If you would like support, please get in touch.
This article provides general guidance only and does not constitute legal advice. Responsible persons should seek professional advice tailored to their specific premises and circumstances. Fletcher Risk Management Ltd is registered in England and based in Chester.