What is passive fire protection?

Passive fire protection (PFP) refers to materials and systems that protect structural elements from fire without requiring activation. It includes intumescent coatings (which swell in heat), fire protection boards, cementitious sprays and concrete encasement. PFP maintains structural integrity during a fire.

How much does intumescent paint cost per m²?

Intumescent paint for 60-minute protection typically costs £25-£40/m² supply and apply. 90-minute protection costs £40-£65/m² and 120-minute costs £55-£90/m². These prices include primer, intumescent coat(s) and topcoat but not surface preparation or access scaffolding.

What is DFT in intumescent coatings?

DFT (Dry Film Thickness) is the thickness of the intumescent coating after drying, measured in mm. The required DFT depends on the fire rating, section factor (Hp/A) of the steel member and the critical temperature. Higher fire ratings and lighter steel sections require thicker coatings.

When should fire protection boards be used instead of paint?

Fire protection boards are preferred when the steelwork will be concealed (ceilings, risers), when a box profile is acceptable aesthetically, or when higher fire ratings (90-120 minutes) are needed cost-effectively. Boards can also be removed and replaced for inspection, unlike spray systems.

Does structural steelwork always need fire protection?

Not always. Single-storey buildings, portal frames in some industrial buildings, and external steelwork may not need fire protection depending on the fire engineering analysis. Also, concrete-filled hollow sections can achieve fire resistance without additional protection.

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Passive Fire Protection Calculator

Calculate quantities and costs for passive fire protection systems including intumescent paint, fire boards, cementitious spray and concrete encasement for steel and timber.

Protection Type

Intumescent paint for visible steelwork

Element Type

Type of structural member

Fire Rating

Required fire resistance period

Section Perimeter

Heated perimeter of section (Hp)

Member Length

Length of each member

Number of Members

Price per m²

Material cost per m\u00B2

How We Calculate This

This calculator estimates the cost of passive fire protection for structural members.

The formula

Total = (Surface area × Material cost/m²) + Labour + Primer

Surface area = perimeter × member length × number of members
Material rate depends on protection type and fire rating
DFT for intumescent paint depends on section factor and fire rating

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.