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Construction compliance guide

Hot Works on Construction Sites: Permits and Fire Prevention

Hot works are one of the leading causes of fire on construction sites. Here is what counts as hot works, how the permit system works, and what you need to do to stay compliant and insured.

What counts as hot works

Hot works is the term used for any operation that produces sparks, naked flames, or enough heat to ignite nearby combustible materials. On a construction site, this covers a wide range of everyday activities:

  • Welding. All types — MIG, TIG, arc, and oxy-acetylene. Welding produces sparks, molten metal, and intense heat that can travel considerable distances and ignite materials well beyond the immediate work area.
  • Flame cutting and oxy-fuel work. Cutting steel with oxy-acetylene or oxy-propane equipment produces showers of sparks and molten slag. The slag can stay hot for a long time and can fall through gaps in floors, igniting materials on levels below.
  • Grinding and disc cutting. Angle grinders and abrasive cutting discs throw sparks up to several metres. On a site with sawdust, packaging, or insulation nearby, a single spark is all it takes to start a fire.
  • Brazing and soldering. These produce less dramatic heat than welding, but a blowtorch directed at pipework near a timber frame, insulation, or plastic fittings can easily cause ignition.
  • Blowtorches and bitumen heating. Roofing work involving bitumen boilers and blowtorches is a common cause of construction site fires, particularly on refurbishment projects where existing combustible materials are close to the work.

Why hot works cause fires on construction sites

Hot works are consistently one of the top causes of fire on UK construction sites. Industry data from the Fire Protection Association shows that hot works account for a significant proportion of large construction site fires, with individual losses regularly running into millions of pounds. Insurance claims related to hot works fires are among the most costly and the most frequently disputed in the construction sector.

The reason hot works are so dangerous on construction sites is straightforward: you are generating sparks and extreme heat in an environment full of combustible materials — timber, packaging, insulation, solvents, waste — and usually without the fire barriers and suppression systems that finished buildings rely on. Sparks from a grinder can travel several metres. Molten slag from a cutting torch can fall through gaps in floors. Conducted heat from a blowtorch can ignite materials on the other side of a wall. And because construction sites change constantly, a work area that was clear of combustibles in the morning may not be clear by the afternoon.

The Joint Code of Practice

The Joint Code of Practice on the Protection from Fire of Construction Sites and Buildings Undergoing Renovation (JCoP) is the recognised industry standard for managing fire risk on construction sites. Published by the Fire Protection Association and endorsed by insurers and the construction industry, it is not law — but it represents best practice, and most construction insurance policies require compliance with the JCoP as a condition of cover.

The JCoP sets out detailed requirements for hot works, including the permit system, clearance distances, fire watch procedures, and the training and competence of operatives carrying out hot works. If you follow the JCoP, you will satisfy the expectations of your insurer and be well on the way to meeting your legal obligations under the Regulatory Reform (Fire Safety) Order 2005 and the Health and Safety at Work Act 1974.

The hot works permit system

A hot works permit is a formal, written document that authorises a specific person to carry out hot works at a specific location for a defined period. The permit system works in three stages:

Who issues the permit

The permit must be issued by a competent person — usually the site manager, site supervisor, or a designated fire safety coordinator. The issuer must physically inspect the area before signing the permit. They should not be the same person carrying out the hot works. On larger sites with multiple contractors, it is good practice to have a single person or team responsible for all hot works permits to maintain consistency and oversight.

What the permit covers

The permit should record the name of the person carrying out the work, the exact location, the type of hot works being done, the start and finish times, the hazards identified, and the precautions in place. It should list the combustible materials that have been removed or protected, confirm that a fire extinguisher is available at the point of work, and specify the fire watch arrangements. A copy of the permit should be kept on site for inspection.

Duration

A hot works permit is typically valid for a single shift or a specific period — never open-ended. At the end of the permitted period, the area must be re-inspected before a new permit can be issued. If conditions change during the work (for example, new combustible materials arrive in the area or the wind picks up), the work must stop and the permit must be reviewed.

Pre-work checks and fire watch

Before hot works begin, the permit issuer and the operative must carry out a thorough check of the work area. Getting this right is the single most effective way to prevent a fire.

  • Remove combustibles. Clear all combustible materials from within at least 10 metres of the work area. This includes timber, packaging, waste materials, insulation, solvents, and anything else that could catch fire. If materials cannot be moved, they must be covered with fire-resistant sheeting.
  • Check adjacent areas. Inspect rooms on the other side of walls, floors above and below, and any voids or cavities that sparks or heat could reach. Molten slag from cutting can fall through gaps in floors, and conducted heat from a blowtorch can ignite materials on the far side of a partition.
  • Fire-resistant sheeting. Where combustible materials cannot be removed, cover them with fire-resistant blankets or sheeting. Ensure the sheeting is properly secured and fully covers the materials, including edges and gaps where sparks could penetrate.
  • Fire extinguisher at the point of work. A suitable fire extinguisher must be positioned within immediate reach of the operative — not at the nearest fire point 30 metres away. The operative must know how to use it.
  • The 60-minute fire watch. After hot works finish, a competent person must remain in the area and monitor it for a minimum of 60 minutes. Many fires start after the operative has packed up and left, when a smouldering ember finally ignites nearby material. Some insurers require a fire watch of up to four hours, particularly in roof spaces and concealed voids.

Occupied buildings and insurance requirements

Hot works in occupied buildings — for example, refurbishment or fit-out work in a building that is still in use — require extra precautions. The building’s occupants may not be aware that hot works are taking place, and the building’s fire detection and suppression systems may be affected by the work. You must coordinate with the building manager, notify occupants where appropriate, and ensure that any fire alarms or sprinkler systems that are temporarily disabled are reinstated as soon as possible. The fire watch period may need to be extended in occupied buildings, particularly where work is being carried out in concealed spaces.

On the insurance side, the position is clear: most construction insurance policies require a formal hot works permit system as a condition of cover. If a fire occurs and you cannot demonstrate that a permit was in place, that the area was properly prepared, and that a fire watch was carried out, your insurer is likely to refuse the claim. The financial consequences can be devastating — not just the cost of the fire damage, but the loss of the contract, delays to the programme, and potential liability claims from the client and other affected parties. Running a proper hot works permit system costs almost nothing. Not running one can cost you everything.

How The Site Book handles hot works in RAMS

When you describe your project in The Site Book, the system automatically identifies whether hot works are likely to be involved. If your project includes welding, cutting, grinding, roofing with bitumen, or any other activity that qualifies as hot works, your RAMS will include the relevant fire prevention controls: hot works permit requirements, clearance of combustibles, fire-resistant sheeting, fire extinguisher provision, and fire watch procedures.

Your Construction Phase Plan will reference the hot works permit system and include it within the wider fire safety arrangements for the project. This is exactly what an HSE inspector, a fire and rescue officer, or your insurer will want to see if they ask for your documentation.

The result is a set of professional compliance documents that already account for hot works fire risk — with the right controls, procedures, and precautions built in. You review it, adjust anything specific to your site, and download documentation that covers your obligations.

Frequently asked questions

Common questions builders ask about hot works permits and fire prevention on construction sites.

What is a hot works permit and when do I need one?

A hot works permit is a formal, written authorisation that must be issued before any work involving flames, sparks, or significant heat is carried out on a construction site. Hot works include welding, flame cutting, grinding, brazing, soldering, the use of blowtorches, and bitumen heating. You need a hot works permit whenever these activities take place outside a permanent, purpose-built workshop with appropriate fire protection. On a typical construction site, that means you need a permit virtually every time hot works are carried out. The permit documents the location of the work, the person carrying it out, the specific hazards identified, and the precautions taken — including clearance of combustibles, provision of fire extinguishers, and arrangements for the post-work fire watch. The permit is usually valid for a single shift or a defined period, after which it must be renewed. Hot works permits are a core requirement of the Joint Code of Practice on the Protection from Fire of Construction Sites, and most construction insurance policies make them a condition of cover. Failing to use a hot works permit system is one of the most common reasons insurers refuse fire-related claims on construction sites.

What is the 60-minute fire watch rule?

The 60-minute fire watch rule requires that after hot works cease, a competent person must remain in the area and monitor it for signs of fire for a minimum of 60 minutes. This rule exists because many construction site fires do not start during the hot works themselves — they start afterwards, when a smouldering ember or spark ignites nearby material that was not visible during the work. The fire watch must be carried out by someone who knows what to look for: smouldering, discolouration, smoke, or unusual smells. The person on fire watch must have a suitable fire extinguisher immediately to hand and must know how to use it. They must also know how to raise the alarm if a fire does break out. The 60-minute period is the minimum recommended by the Joint Code of Practice, but some insurers and clients require a longer period — up to four hours in some cases, particularly for work in roof spaces, voids, or areas with concealed combustible materials. Always check your insurance policy and site-specific fire plan for the required fire watch duration.

Who can issue a hot works permit on site?

A hot works permit should be issued by a competent person who has the authority and knowledge to assess the fire risks in the area where the work will take place. On most construction sites, this is the site manager, site supervisor, or a designated fire safety coordinator. The person issuing the permit must physically inspect the area before authorising the work. They need to confirm that combustible materials have been removed or protected, that fire-resistant sheeting is in place where needed, that a suitable fire extinguisher is available, and that the operative carrying out the hot works understands the precautions and the fire watch requirements. The permit issuer must also check adjacent areas — including rooms on the other side of walls and floors above and below — for combustible materials that could be ignited by conducted heat or sparks travelling through gaps. On larger sites with multiple contractors, it is good practice to appoint a single person or a small team responsible for all hot works permits, to avoid confusion and ensure consistency. The person issuing the permit should not be the same person carrying out the hot works.

What fire extinguisher do I need for hot works?

The type of fire extinguisher required for hot works depends on the materials present in the immediate area. As a general rule, you should have at least one extinguisher rated for Class A fires (ordinary combustibles such as wood, paper, and textiles) and one rated for Class B fires (flammable liquids) within arm’s reach of the operative. A water extinguisher or water mist extinguisher covers Class A risks, while a dry powder extinguisher covers Class A, B, and C (flammable gas) risks and is the most versatile option for construction site hot works. If hot works are being carried out near electrical installations, a CO2 extinguisher should also be available. The Joint Code of Practice requires that fire extinguishers for hot works are positioned immediately adjacent to the work — not at the nearest fire point 30 metres away. The operative and the fire watch person must both know how to use the extinguisher. Extinguishers must be in-date, serviced, and fully charged. After the hot works, the fire watch person must have the extinguisher with them for the full duration of the fire watch period.

Does my insurance require a hot works permit?

Almost certainly, yes. The vast majority of construction insurance policies in the UK include a hot works warranty or condition that requires you to operate a formal hot works permit system in line with the Joint Code of Practice on the Protection from Fire of Construction Sites. If you carry out hot works without a permit and a fire occurs, your insurer may refuse the claim entirely — even if the fire was not directly caused by the hot works. This is not a theoretical risk: insurers regularly decline claims worth hundreds of thousands of pounds because the contractor could not produce evidence that a hot works permit system was in operation. The typical insurance requirements include: a written hot works permit for every instance of hot works, clearance of combustibles before work begins, provision of fire extinguishers at the point of work, a fire watch of at least 60 minutes after the work finishes, and records of all permits issued. Some policies go further and require specific training for anyone carrying out or supervising hot works. Check your policy wording carefully — and if in doubt, ask your broker. The cost of running a proper hot works permit system is negligible compared to the cost of an uninsured fire.

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