Overview
Intumescent coatings are used to help protect structural elements and support required fire resistance performance. From a client perspective, the risk is usually not “did we apply paint?” - it’s whether the work was planned and checked to the system requirements.
What intumescent coatings are (plain English)
Intumescent coatings are applied to certain structural elements to help delay temperature rise and support a required fire resistance period.
In practice, the client-side questions are:
- what elements are in scope and what rating is required
- what system/product is specified
- how you’ll know the correct thickness and coverage has been achieved
What affects performance
| Factor | Why it affects outcome | What to do client-side |
|---|---|---|
| Substrate + preparation | Poor prep can lead to adhesion failure | Agree preparation standard and inspection hold points |
| Specified system + rating | Product choice depends on required performance | Confirm rating and system reference up front |
| Application conditions | Temperature/humidity can affect curing | Plan working conditions and record them if required |
| Film thickness | Under-thickness can reduce performance | Require thickness checks and a non-conformance process |
| Previously coated/contaminated steel | Unknown compatibility and prep risk | Survey, document, and agree treatment method |
| Follow-on trades | Impact and overcoating can damage coatings | Protect/sequence works and record any touch-ups |
| Access constraints / missed faces | Missed faces undermine the member protection | Use a scope schedule with “faces in scope” clearly shown |
What to ask for (scoping)
- scope schedule: which members, locations, and faces are included
- required fire resistance period (as project documentation/strategy requires)
- system/product reference (including primer/topcoat where applicable)
- access plan (working at height, out of hours, resident/staff coordination)
QA: what “good” looks like
QA should be agreed up front and should usually include:
- surface prep checks
- environmental condition checks (where relevant)
- film thickness verification (dry film thickness checks) to the system requirements
- a process for non-conformances (what happens when thickness is short)
QA outputs you should expect
| QA item | What “good” looks like |
|---|---|
| Scope schedule | Member ID/location + faces treated + required rating |
| Product/system confirmation | Primer/base/topcoat references (as applicable) |
| Prep evidence | Visual checks + notes on contamination/repairs |
| Thickness verification | Dry film thickness readings recorded against locations |
| Non-conformance log | What was short, what was done to correct it |
| Close-out photos | Representative wide shot + close-up per area |
Interfaces that often break the outcome
Even well-applied coatings can be compromised by:
- late design changes (members added/removed or rating changes)
- follow-on trades damaging surfaces
- access constraints leading to “missed faces” (especially near walls/ceilings)
If you’re coordinating multiple contractors, make sure the protection is sequenced and protected.
What to ask for (handover documentation)
- confirmation of the specified system and required rating (as project documentation requires)
- preparation approach (including treatment of previously painted surfaces)
- QA approach and what will be recorded
- close-out documentation for your compliance file
At a sensible minimum, ask for:
- scope summary (what elements were treated)
- product/system details and batch references (as appropriate)
- thickness / inspection records (where applicable)
- photo record of representative areas
- notes on exclusions, access constraints, and follow-on actions
A simple evidence pack checklist
| Item | Why you want it |
|---|---|
| Scope summary | Confirms what was and wasn’t treated |
| System/product references | Lets you defend suitability later |
| Thickness records | Provides measurable assurance |
| Photos | Supports future audits and repairs |
| Constraints/exclusions | Prevents false confidence |
How it works
- Confirm requirements — rating, elements in scope, system reference.
- Survey and plan access — map locations and constraints.
- Prepare surfaces — in line with system requirements.
- Apply and QA — verify thickness and coverage.
- Close out — deliver an evidence pack that is searchable and auditable.
Common problems to watch for
- unclear scope (members missed, faces missed)
- poor preparation leading to adhesion issues
- damage after installation from other trades
- no thickness evidence, making future assurance difficult
If existing coatings have no records
When you inherit previously coated steel with limited documentation, treat it as an unknown and agree a proportionate verification plan.
| Option | When it’s used | What to record |
|---|---|---|
| Targeted verification | Localised areas, low disruption | Locations checked + results + assumptions |
| Engage a specialist / manufacturer advice | Unclear system compatibility | Advice received + product references |
| Strip and re-specify | High uncertainty or poor condition | Scope, disposal/containment approach, new QA pack |
FAQs
Can we just touch up damaged areas?
Sometimes, but compatibility matters. Touch-ups should follow the system requirements and be recorded clearly, especially where thickness is critical.
Do we always need thickness readings?
Where the system relies on achieving specific film thicknesses, thickness verification is typically a key part of QA. Agree the evidence standard up front.
What’s the simplest way to avoid disputes later?
A clear scope schedule and a close-out pack that links each treated element to evidence (records and photos). It’s much easier than reconstructing what happened months later.
What should we do if we discover previously coated steel with no records?
Treat it as an unknown: record locations, photograph conditions, and seek competent advice on verification options and what evidence is reasonable to retain going forward.
Can we paint over intumescent coatings later?
Potentially, but it should be controlled. Overcoating can affect performance and may need to follow the original system guidance. If future decoration is likely, agree how it will be managed and how changes will be recorded.