How to Write a Permit to Work for Hot Works on Site

The problem with most hot works permits on site

Hot works — welding, grinding, cutting, torch-applied roofing — are responsible for a significant proportion of construction site fires. The permit to work system exists to control that risk, but on most sites the permit is treated as a box-ticking exercise: printed, signed in thirty seconds, and forgotten about until something goes wrong.

If you're a site supervisor, foreman or engineer responsible for issuing permits, this guide walks you through what a hot works permit to work actually needs to contain, how to issue one properly, and how to avoid the mistakes that leave you exposed if there's an incident.

What is a permit to work for hot works?

A permit to work (PTW) is a formal, written document that authorises specific high-risk work to take place under defined conditions. For hot works, it records:

• What work is being done and by whom
• Exactly where on site it's happening
• The date, start time and permitted duration
• Hazards identified and control measures in place
• Who has authorised the work
• The post-work fire watch requirements
• Sign-off when the work and fire watch are complete

It's not a risk assessment, though it should reference one. It's not a method statement, though both should exist alongside it. The permit is specifically about granting controlled, time-limited permission for the work to happen on that particular day, in that particular location.

Step-by-step: how to write a hot works permit correctly

1. Identify the work scope precisely

Start with exactly what hot works activity is taking place. "Welding on Level 2" is too vague. "Oxy-acetylene cutting of structural steelwork on Level 2 grid lines C3–C5, south elevation" is what you need. Vague scope means the operative can interpret the permit broadly — that's how fires start in areas the issuer never considered.

Record the operative's name and their relevant competence or certification (CSCS card type, welder qualification, etc.). If you can't verify their competence, don't issue the permit.

2. Carry out a pre-work inspection of the area

Walk the area before issuing the permit. You're looking for:

• Combustible materials within 5 metres — timber, packaging, insulation, solvents
• Hidden voids, service ducts or gaps in floors and walls where sparks or molten metal could travel
• Nearby flammable substances or gas supplies
• Sprinkler or fire detection systems that may need to be isolated (and whether you have authority to do that)
• Adjacent occupied or sensitive areas

Take photos during this walk. They're evidence that you actually looked — and they're useful if you need to demonstrate due diligence later.

3. Set out your control measures specifically

This is where most permits fall down. "Fire extinguisher on standby" is not adequate. Your permit should state:

• Type and size of extinguisher (CO₂, dry powder, water mist — appropriate to the materials present)
• Exact location of the extinguisher
• Whether a fire watch operative is required and who that person is
• Clearance distances maintained (minimum 5 metres of non-combustible space)
• Whether combustibles have been removed, covered with fire-resistant sheets, or wetted down
• Whether fire detection in the area has been isolated — and if so, the compensatory measures and who authorised the isolation
• Communication method between operative and fire watch

4. Set the permitted time window

A hot works permit should have a clear start time and an end time for the hot works activity itself. Do not issue open-ended permits. If the job overruns, the operative should stop and you should issue a new or extended permit — that forces another check rather than assuming conditions haven't changed.

5. Ensure the right person signs it

The issuing authority must be someone with the knowledge and site authority to assess that the conditions are safe and the controls adequate. That's usually the site manager, site supervisor or a designated permit issuer. The operative doing the work should not be the person issuing their own permit — that defeats the entire purpose of the system.

Both the issuer and the operative should sign the permit before work starts, confirming they've both understood the conditions.

6. Conduct and record the fire watch

This is the step most sites skip or do badly. When hot works stop, the fire watch must continue — typically for a minimum of 60 minutes after work finishes, though some insurers and fire risk assessors require longer (up to two hours for work involving voids or combustible substrates).

The fire watch operative must remain in the area, must have a means of raising the alarm, and should check adjacent areas including below the work location. Record the name of the fire watch operative on the permit.

7. Close the permit out properly

A permit to work must be formally closed. Once the fire watch period is complete and no fire risk has been identified, the issuer or another authorised person signs the permit closed, with the time recorded. File it — do not throw it away. If an insurance claim or HSE investigation ever arises from a fire that started hours after the work, that signed, closed permit is your evidence that the system worked correctly.

Common mistakes that invalidate your permit system

• Pre-signing blank or incomplete permits — this happens when permits are signed at the start of the day before anyone has inspected the work area. Invalid.
• No fire watch, or fire watch done by the operative themselves — the fire watch must be a separate, dedicated person during the watching period.
• Reusing the same permit — each day, each location requires a fresh permit.
• No reference to nearby fire detection isolation — if a detector has been taken offline, this must be recorded and compensatory measures must be documented.
• Permits not retained after completion — retain permits for at least three years as part of your safety records.

Linking your permit to your risk assessment and method statement

Your hot works permit doesn't exist in isolation. It should reference (or be accompanied by) a specific risk assessment for hot works and, where the task is complex or involves multiple operatives, a method statement. The permit is the day-by-day control mechanism; the risk assessment is the underlying evidence that the risks have been properly thought through.

If you need to produce those supporting documents quickly on site, Safety Parrot can generate structured risk assessments and method statements from your site photos in seconds — useful when a subcontractor turns up without the paperwork and work can't start until it's in place.

A template checklist before you sign any hot works permit

1. Work scope and location are specific and unambiguous
2. Operative's name and competence recorded
3. Pre-work inspection of the area completed and documented
4. Combustibles removed or protected
5. Correct extinguisher type confirmed and located
6. Fire watch operative named
7. Fire detection status confirmed (active or isolated with compensatory measures)
8. Start and end time set
9. Both issuer and operative have signed
10. Post-work fire watch duration specified
11. Permit closure signed off after fire watch
12. Completed permit retained in safety file

Getting the permit to work right isn't about paperwork for its own sake. It's about making sure the conversation actually happens — that someone has walked the area, thought through the risks, and confirmed that the right controls are genuinely in place before a flame or a spark enters the equation.