Fire resistance and fire safety are crucial considerations to be made during construction planning; it’s the second thing building regulations cover only after ‘Structure’! Structural steel beams can be found in many modern construction projects, so in this blog we take a look at how steel can be made more fire resistant to meet building regulations. So, what are the options for providing additional structural steel fire protection?
Structural steel is inherently fire-resistant, but this property can be increased via:
- Fire protection boards — non-combustible sheets that stick to unpainted steel
- Fire protection sprays — paint-like coating that adds a thin layer of insulation
- Intumescent coatings — paint-like coating that expands when exposed to extreme heat
Keep reading to discover the properties of each structural steel fire protection option, as well as our in-depth guide to fire safety building regulations.
Why Structural Steel Needs Fire Protection
The fire-resistance properties of steel can often fail to meet the requirements for a project. You might find this surprising, considering that steel is still one of the best materials for structural construction because of its inherent elemental resistances.
The fact is, though, that steel loses strength the hotter it gets, with small, fully-loaded sections resisting for as little as 12 minutes before failing when exposed on all sides.
Construction methods and intumescent coatings can be used in the application of structural steel to increase its fire resistance to a more acceptable level as defined by Fire Safety: Approved Document B (usually around 60–120 minutes depending on the specific building type and use).
Common Structural Steel Fire Protection Methods
Passive structural steel fire protection materials are categorised, typically, as either ‘non-reactive’ or ‘reactive’.
| Common fire protection materials | ||||
| Non-reactive | Reactive | |||
| Boards | Sprays | Intumescent coatings | ||
| Thick film coatings | Thin film coatings | Off-site applied coatings | ||
Fire Protection Boards
Boards are used for fire protection in, both, visible and hidden areas, thanks to their versatile shape and aesthetics. The properties of boards that make them great for structural steel fire resistance include:
- Made from non-combustible materials such as calcium silicate, gypsum, or mineral fibre
- Have a consistent thickness
- Can be applied to unpainted structural steel
- Typically affordable and versatile
Fire Protection Sprays
Sprays are an acceptable option for adding fire resistance to a building, but they are not the most popular choice. Sprays can be particularly suitable for projects with lots of exposed steel beams where aesthetics are less of a priority. The properties of fire protection sprays include:
- Able to coat complex shapes such as structural steel beams
- Additional labour is required to deal with overspray and clean floors after spraying
- Not aesthetically pleasing
- Application of sprays is a wet trade which may impact site operations
Intumescent Coatings
Intumescent coatings are paint-like materials that offer incredible fire resistance for complex shapes such as steel beams. Intumescent coatings are inert at low temperatures but expand when exposed to high temperatures to form a low-conductivity char layer, making them distinct from fire-protection sprays.
There are two types of intumescent coatings—thin film and thick film—each with its own material makeup and applications.
Thin Film Intumescent CoatingsThin film intumescent coatings are either solvent- or water-based, and are used for protecting most types of buildings against fire. Most commonly, thin film intumescent coatings are deployed when fire resistance of between 30–90 minutes is required. Thin film coatings typically have an expansion rate of 50:1, meaning a 1mm-thick coating will expand to 50mm when in contact with heat. |
Thick Film Intumescent CoatingsThick film intumescent coatings are typically epoxy-based, drying to form a thicker layer of film that is more durable than thin film coatings, providing a longer fire resistance time. Thick film coatings are used when the environment is too extreme for thin film coatings, such as on a skyscraper’s external steel or in exposed marine environments. Thick film coatings typically have an expansion rate of 5:1, meaning a 1mm-thick coating will expand to only 5mm when in contact with heat |
On-site and Off-site Coating Applications
Intumescent coatings can be applied to steel beams (or other relevant structural components) on-site or off-site, though there are particular benefits to off-site application, such as:
- Better quality control
- Less work timeline disruption
- Cleaner worksites
- Better worksite safety
- Easier installation
The downsides of off-site application are:
- Less aesthetic result
- More expensive than on-site application (though the long-term benefits often outweigh the upfront costs)
- Off-site application of thin film coats can be highly specialised
Fire Regulations For Steel Structures in the UK
The primary building regulations for fire resistance in buildings can be found in Approved Document B; there are two volumes:
Approved Documents are collections of practical advice on how to meet the minimum requirements of Building Regulations 2010 in England, approved by the Secretary of State.
| Following the guidance in the Approved Documents is not the same as meeting the requirements for building regulations, but the Approved Documents do quote relevant requirements to help your understanding. |
Below we have listed the requirements outlined by Building Regulations relating to fire safety in buildings as they appear in Approved Document B:
Requirements of Building Regulations for Fire Safety
Requirement B1
When there is a fire, ensure both:
- Satisfactory means of sounding an alarm
- Satisfactory means of escape for people
Requirement B2
Inhibit the spread of fire over internal linings of buildings.
Requirement B3
The building must be built such that all of the following are achieved in the event of a fire:
- The premature collapse of the building is avoided
- Sufficient fire separation is provided within buildings and between adjoining buildings
- Automatic fire suppression is provided where necessary
- The unseen spread of fire and smoke in cavities is restricted.
Requirement B4
Restrict both:
- The potential for fire to spread over external walls and roofs (including compliance with regulations 6(4) and 7(2))
- The spread of fire from one building to another.
Requirement B5
Ensure both:
- Satisfactory access for the fire service and its appliances
- Facilities in buildings to help firefighters save the lives of people in and around buildings
Regulation 38
Provide fire safety information to the building owner.
Enduring Fire-Resistant Structural Steel from STEELO
If you’re trying to meet your project’s fire resistance requirements, STEELO is here to advise on your best options for structural steel fire protection, as well as fabricate and supply the beams you need.
Get in touch today to discuss your project specifications, or browse our full range of steel beams, prefab structures, and steel finishes online.
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