> Disclaimer: SiteKiln gives you plain-English information, not legal or health and safety advice. Always follow your site-specific risk assessments and talk to a qualified professional.
The short version
On construction sites, any hot work (welding, cutting, grinding, torch-on roofing, etc.) should only go ahead under tight control, usually using a hot-work permit system and proper fire precautions.
HSG168 and the Joint Code of Practice both put the duty on those in control -- client, principal contractor, and site management -- to avoid hot works where possible, and where they can't, to control them through permits, competent people and fire watches.
Why it matters
Most of the big construction fires you read about start with hot works: roof torches, grinders, cutting, soldering, welding, or brazing near combustibles.
Once a fire takes hold in timber frames, voids or cladding, you can lose an entire block and put lives at risk, with the principal contractor, key subs and sometimes the client in the frame under fire and health and safety law -- and insurers leaning hard on the Joint Code.
So insurers, HSG168 and the Joint Code now expect hot works to be treated as high-risk and only done when justified, controlled and watched -- not as just another job on the list.
What counts as "hot work" on site
HSG168 and the Joint Code treat hot work as any activity that uses or creates open flames, high temperatures or sparks that could start a fire.
Typical examples:
- Gas or electric welding and cutting.
- Grinding, disc cutting and metal cutting that throws sparks.
- Soldering, brazing and burning off.
- Torch-on roofing and some drying operations.
- Some use of hot-air tools where they can ignite materials.
The Joint Code also pushes for design and method choices that avoid hot works on site where possible -- e.g. prefabrication, mechanical fixings, cold-applied products.
Who is responsible for hot works controls
Between HSG168 and the Joint Code, responsibilities look roughly like this:
Client and designers:
- Expected to design out hot works where reasonably practicable -- e.g. specify cold-applied roofing systems or mechanical fixings instead of torches and naked flames.
Principal contractor / main contractor:
- Must include hot-work controls in the fire safety plan and Construction Phase Plan.
- Decide where hot works are allowed, and where they are banned or require extra controls.
- Operate a hot-work permit system where needed, and monitor compliance.
Permit issuer / fire safety lead:
- Competent person with authority (often site manager or H&S manager) who reviews each hot-work task, checks controls, and issues/ends permits.
Contractors doing the hot work:
- Must plan the job, provide competent operatives, follow the permit conditions and keep the area safe before, during and after the job.
Fire watch:
- Named person(s) who monitor the area during hot works and afterwards for signs of smouldering, in line with HSG168/Joint Code guidance.
Everyone on site has to obey hot-work rules once they exist -- but the system itself is on those in control.
What a hot-work permit should actually cover
A permit is just a written control system -- but it needs to be real, not just a laminated template in the folder.
A decent hot-work permit will normally specify:
Exact location and nature of the work
- Where, what process, and for how long the permit is valid.
Permit issuer and competent operative
- Who authorised it and who is doing the work -- both should be competent for hot works and the risks.
Pre-work fire checks
- Combustibles cleared from the area, including behind/under/above the work where sparks or heat could travel.
- Openings and gaps covered with fire-resistant materials where needed.
- Gas and fuel systems safe and stable; cylinders upright and secured.
- Nearby detectors/sprinklers managed appropriately (isolated and then re-enabled once work is done, as per the fire plan).
Fire-fighting equipment
- Suitable extinguishers present, in date, and close at hand (e.g. water/foam for general materials, CO2 for electricals).
- Operatives and fire watch trained in how to use them.
Fire watch and post-work checks
- Named fire watch responsible during the work and for a continuous watch for at least 60 minutes after hot works stop, plus a further re-inspection around an hour later (as per updated HSG168/Joint Code guidance).
- Any increased fire watch time where the risk assessment says so (e.g. voids, timber frames).
Sign-off
- Confirmation that the area has been checked, hot works stopped, gear made safe, and the permit closed.
The Joint Code and HSG168 now both stress the importance of that post-work fire watch -- many big fires start long after the bloke with the torch has gone home.
Your responsibilities if you're doing hot works
If you or your firm are the ones with the torch, welder or grinder:
- Make sure there is a permit where the site rules or risk assessment require one -- if there isn't, ask the site manager; don't just crack on.
- Read it and follow it -- including clearing combustibles, protecting openings, having the right extinguishers, and stopping when conditions change (e.g. wind, materials moved).
- Stay in the area for the agreed fire-watch period after finishing and do the re-check -- don't sign off and drive away immediately.
- If the work can be done safely using cold methods instead (mechanical fixings, cold-applied products, pre-fabrication), raise that as an option -- both HSG168 and the Joint Code push for hot works to be a last resort.
If a site has no hot-work rules at all and you're being asked to torch or weld in risky places with no controls, that's a red flag for both fire safety and insurance compliance.
Is this hot work under control?
Before you light up, check:
Is hot work actually necessary? Have you confirmed there isn't a reasonably practicable cold method (mechanical fixing, cold-applied product, prefabrication) instead?
Is there a valid permit for this job and location? Has a competent person authorised today's hot work, for this exact area and task, with clear conditions and time limits?
Is the area properly prepared? Combustibles cleared or protected (including behind/under/above), gas/fuel set up safely, and any affected fire protection managed as per the fire plan.
Is suitable fire-fighting kit and a fire watch in place? Correct extinguishers are at hand and operatives/fire watch know how to use them; a named fire watch will stay during the job and for at least the specified post-work period (typically 60 minutes plus a re-check).
If you can't honestly say yes to all four, the hot work isn't being controlled to the standard HSG168 and the Joint Code expect.
What to do next
- Check whether a cold method (mechanical fixing, cold-applied product) could replace hot works on your next job -- both HSG168 and the Joint Code push for this.
- If hot works are unavoidable, make sure you've got a working permit system and that a named fire watch will stay for at least 60 minutes after the work stops.
- Clear all combustibles from the area before you light up, including behind, under and above the work point.
- Make sure the right extinguishers are at hand and that everyone involved knows how to use them.
- If the site has no hot-work rules at all, raise it with the site manager before you start -- don't just crack on.
Sources
- Regulatory Reform (Fire Safety) Order 2005 -- fire safety duties on the responsible person.
- Construction (Design and Management) Regulations 2015 -- planning and management duties.
- Health and Safety at Work etc. Act 1974 -- general duties.
- HSE -- HSG168 Fire Safety in Construction (3rd edition).
- Joint Code of Practice on the Prevention and Management of Fire in Construction Sites and Buildings Undergoing Renovation.
Disclaimer
This guide is general information for small UK construction businesses and trades, not formal legal, insurance or fire-engineering advice.
SiteKiln is not a law firm and this page is not a substitute for getting advice on your specific situation.
Fire safety law and guidance, including HSG168 and the Joint Code, are updated from time to time, and how they apply will always depend on the exact facts on your project and your role.
If you're dealing with high-risk hot works, complex sites, insurer warranties or a fire incident, get specific advice from a competent fire safety professional and/or solicitor before you make big decisions.
Know someone who needs this?
Was this guide useful?
Didn't find what you were looking for?
Spotted something wrong or out of date? Email us at hello@kilnguides.co.uk.
In crisis? Samaritans 116 123 ·