If you're planning a construction project that involves structural steel, intumescent fire protection is almost certainly going to be a requirement. But how much should you budget for it? In this guide, we break down the real costs involved and explain what drives the price up or down.
What is Intumescent Fire Protection?
Intumescent coatings are specialist fire protection paints applied to structural steel. When exposed to heat, they expand (intumesce) to form an insulating char layer that protects the steel from reaching its critical failure temperature. Without protection, structural steel can lose its load-bearing capacity within minutes during a fire.
Building regulations require structural steel to achieve fire ratings of 30, 60, 90, or 120 minutes depending on the building type, occupancy, and use. Intumescent coatings are the most common method of achieving this.
Typical Costs Per Square Metre
Intumescent fire protection is typically priced per square metre of steel surface area. The cost varies significantly depending on the fire rating required, the complexity of the steel, and site access conditions.
| Fire Rating | Cost per m² (supply & apply) | Typical DFT |
|---|---|---|
| 30 minutes | £25 – £45/m² | 250 – 500 µm |
| 60 minutes | £40 – £75/m² | 500 – 1,200 µm |
| 90 minutes | £65 – £110/m² | 1,000 – 2,000 µm |
| 120 minutes | £90 – £150/m² | 1,500 – 3,500 µm |
Note: These are guide prices for 2026. Actual costs depend on project-specific factors outlined below.
What Affects the Price?
1. Fire Rating Required
The higher the fire rating, the thicker the coating needs to be. A 120-minute rating can require 3–4 times the material thickness of a 30-minute rating, meaning more coats, more material, and more labour time.
2. Section Factor (Hp/A)
The section factor is the ratio of the heated perimeter to the cross-sectional area of a steel member. Lighter, thinner sections have higher section factors and require thicker coatings to achieve the same fire rating. A UC152x152x23 column will need significantly more coating than a UC305x305x137 column for the same fire rating.
3. Access and Working Conditions
If the steel is at height, in confined spaces, or requires scaffold access, costs increase. Working around other trades on a live construction site also affects productivity. The ideal scenario is coating steel at ground level before erection — but this isn't always possible.
4. Surface Preparation
New steel with a clean shop primer is straightforward. Existing steel that's been painted, corroded, or contaminated requires additional preparation — wire brushing, grinding, or even blast cleaning — which adds to the cost.
5. Location and Mobilisation
Travel distance, accommodation, and the number of mobilisations required all factor into the price. A single mobilisation for a large project is more cost-effective than multiple visits to a smaller site.
6. DFT Testing and Certification
All intumescent coatings must be independently tested for dry film thickness (DFT) and certified. This includes DFT readings on every member, batch certificates, fire test certificates, and a certificate of conformity. Reputable contractors include this in their price — be wary of quotes that don't.
Example Project Costs
To give you a real-world sense of pricing, here are some typical project scenarios:
| Project Type | Steel Area | Fire Rating | Budget Range |
|---|---|---|---|
| Small extension (8 columns) | 15–20 m² | 60 min | £4,000 – £7,000 |
| Care home conversion | 40–60 m² | 60 min | £8,000 – £14,000 |
| Commercial warehouse | 150–300 m² | 60 min | £20,000 – £40,000 |
| Multi-storey residential | 200–500 m² | 90–120 min | £35,000 – £80,000 |
How to Get an Accurate Quote
To provide an accurate quotation, a specialist contractor will need:
- Structural drawings showing steel sizes and locations
- Fire engineering report or building control requirements (fire rating per member)
- Site access information and programme
- Whether the steel will be coated before or after erection
With this information, a contractor can calculate the exact DFT required for each member, determine the surface area, and provide a fixed-price quotation rather than a budget estimate.
What Should Be Included in a Quote?
A professional intumescent coating quotation should include:
- Full steel schedule with section sizes and surface areas
- DFT schedule showing required thickness per member
- Coating system specification (product, primer, topcoat)
- Surface preparation method
- DFT testing and certification
- Programme and mobilisation details
- Clear inclusions and exclusions
If a quote doesn't include these elements, it's likely either incomplete or the contractor doesn't fully understand the specification.
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