Firestopping to structural steel: intumescent coatings
Steel protected to the fire-resistance period your fire strategy asks for, evidenced before cover-up and handed over with a complete evidence pack.
BM TRADA Q-Mark certified firestopping installer · Greater London & the M4 corridor
Third-party certified — BM TRADA Q-Mark
Landmark London projects: The Gherkin, Grosvenor Square, Olympic Park
Specified per member, proved per member
Send the steel schedule and the fire strategy. You get a thickness against every member, and a record that shows what actually went on.
Periods from the fire strategy
Required periods taken from the strategy, not assumed from the storey. Transfer structure can require separate checking.
Section factors taken off
Every member's Hp/A read off the steel schedule, with the correct three or four-sided exposure for how it sits.
Thickness set per member
The system's assessment gives the thickness for that section factor and period. A slender beam and a heavy column differ.
Applied, gauged, recorded
Readings logged against the member reference before anything is boxed in or the ceiling closes the soffit.
The dry film thickness record
Not a certificate saying the work was done. A member-by-member record of what was specified against what was measured on the steel.
Scroll for specified and measured thickness →
| Member | Element | Exposure | Section factor Hp/A | Period | Specified | Measured |
|---|---|---|---|---|---|---|
| Column | Column | 4-sided | — | Per fire strategy | Per assessment | Recorded on site |
| Beam | Beam | 3-sided | — | Per fire strategy | Per assessment | Recorded on site |
Client feedback and enquiry
They were always available to answer any questions and were proactive in keeping me informed throughout the project.
Not sure the steel package is covered?
Send us the steel schedule and fire strategy. We will tell you what is specified, what is missing and where boarding is the better answer.
Contact usCoating or boarding?
Intumescent coatings and board systems both give fire protection of steel for a set fire-resistance period. They differ on appearance, programme position and how easily the finished work can be checked.
Intumescent coating
Sprayed or applied to the profile, then topcoated. The steelwork stays visible as steelwork.
- Keeps the section profile — the usual choice on exposed steel
- Thickness set per member, not one blanket depth
- Can be shop-applied off site to protect the programme
- Finished thickness is measurable, so it can be verified later
Board encasement
Rigid boards fixed around the member to form a box. The steel is enclosed rather than coated.
- Boxes the section — fine where the steel is concealed anyway
- Less sensitive to site conditions during installation
- Often pragmatic for complex junctions and long periods
- Takes up more space, which matters in tight risers
Steel does not burn. It softens.
Intumescent paint is a reactive coating: it stays thin at room temperature, then swells into an insulating char once a fire heats it, slowing a steel member's temperature rise so it holds its strength for the period the fire strategy asks for. Our guide to the intumescent meaning covers the chemistry in more depth. As a member heats through a fire its strength falls away, and design works to a limiting temperature based on how hard that member is working. Unprotected, an exposed beam can reach that limit well inside the period the building has to stand up for. That is a structural fire-resistance question, separate from the What Is Compartmentation? Fire Compartmentation Explained lines that stop a fire spreading between rooms and floors.
On site people often ask for intumescent painting contractors, because the material goes on like paint. Skyline records the work as Intumescent Coatings, because a tested system assessed under the EN 13381 series is what actually gets specified, applied and measured against each member, not a paint job.
How much does intumescent paint cost? It is priced per steel member, not per square metre — the section factor and the required fire-resistance period set the thickness for each member, and the thickness sets the material and labour. A single rate quoted across a whole frame is a warning sign, not a saving. The commercial risk is quieter. Coatings get priced off a schedule, and undocumented application creates risk once it is covered by ceilings. Then the fire engineer asks which system went on which member, and to what thickness. A delivery note is not an answer, and protection that cannot be evidenced becomes Remedial Firestopping rather than a straightforward sign-off. On a higher-risk building that record has to survive into the golden thread and still hold up years later, long after the people who did the work have moved on. Skyline works as intumescent paint contractors and structural steel fire protection specialists, applying intumescent coatings for steel across Greater London and the M4 corridor.
Intumescent coatings, answered
How thick does intumescent coating need to be?
There is no single answer. Thickness comes from each member's section factor and the required period, using the assessment for that system. A single figure quoted across a whole frame should be checked against the member-level take-off, unless the system's assessed specification is genuinely uniform for that project.
Can it be applied off site?
Often, yes. Shop application under controlled conditions takes the work off the critical path and gives a more consistent finish, with transport and erection damage made good on site. It needs agreeing early.
Do you cover our project area?
Greater London and the Thames Valley / M4 corridor, including Reading, Henley, Newbury, Maidenhead, Windsor, Slough, Oxford, Swindon and Watford. If you sit at the edge of that area, call and ask.
Read next
Send us the steel schedule
Send the schedule and the fire strategy. You get section factors, periods and a priced thickness against every member. Where boarding is the better answer, we will say so. BM TRADA Q-Mark certified · experience on The Gherkin, Grosvenor Square & Olympic Park.