Structural Steel Fire Protection

Intumescent Paint

Intumescent-PaintThin film Intumescent coatings can provide a durable and attractive surface, similar to a paint finish. However, in a fire the Intumescent will expand to many times its original thickness. This provides an insulating foam-like char to protect the steelwork against heat build-up.

Intumescent basecoats are available in Water or Solvent based systems and when applied to correctly prepared & primed steel will offer a robust and cost effective solution for fire ratings of 30, 60, 90 & 120. When calculating the product requirements the following key factors will apply:

Fire rating required:
30, 60, 90 or 120 minutes

Type of section:
Universal, hollow, beams or columns

Steel exposure:
Partial exposed, 3-sided or 4 sided

Size and weight of steel:

The Hp/A value is known as the section factor of the steel section. This section factor is directly related to the heating rate of the steel section under a fire condition.

Hp – The perimeter of the steel exposed to the fire
A – The cross sectional area of the section

The larger the surface area relative to the cross sectional area, the higher the Hp/A value, the higher the Hp/A value, the more material required. This means that the thicker the section, the slower it is to heat up consequently the less thickness of material required.


All manufacturers are able to offer a comprehensive range of protective and decorative topcoats to protect the Intumescent basecoat from corrosion attack and are available in a wide range of RAL and BS4800 colours. All structures have a Corrosion building classification depending on the environments they are as follows:

C1: Very low corrosion risk, warm dry interior such as offices, schools & hospitals etc,
C2: Low corrosion risk, steelwork exposed to moisture such as vehicle depots, sports halls etc
C3: Medium corrosion risk, steelwork exposed to moisture and pollution such as Breweries, swimming pools

Within a Category 1 environment a topcoat will not be required unless the Intumescent will be visible and the client requires a decorative/coloured finish.

Fire Boarding

Whilst not undertaking any wall, floor or ceiling linings, MGN have and will undertake steelwork encasement to universal beams and columns upon request using robust boarding systems such as Glasroc F from British Gypsum and mineral fibre boards from Rockwool