How to Specify Intumescent Coatings for Structural Steel

A clear intumescent coating specification allows the design team, coating manufacturer, tenderers, applicator and inspector to work from the same requirements. A vague specification can produce incomparable quotations and leave important design responsibility unresolved.

This article is a coordination checklist, not a fire-engineering design. The responsible fire engineer, structural engineer and design team should determine the project-specific performance before the application work is procured.

Start with the design basis

State the documents and assumptions that define the structural fire-protection requirement. These may include the fire strategy, structural fire design, relevant drawings, steel schedule and the applicable version of regulatory guidance.

For work in England, refer to the current Approved Document B collection and confirm which edition and transitional provisions apply. Other UK nations have their own regulatory guidance.

The specification should identify the required fire-resistance performance by element or zone. It should not rely on a blanket assumption based only on the building type.

Provide the steel information

Tenderers need an accurate schedule of the members to be protected. Include:

• Member references and section sizes
• Drawings showing the extent of treatment
• Section factors and the number of exposed sides
• The design or limiting temperature used for each member
• Connections, cellular beams or other details requiring specific assessment
• Areas that will be concealed or become inaccessible

Section factor affects the heating rate of the member and therefore the required coating build. SteelConstruction.info explains how section factors are calculated and why exposure conditions matter.

Define the approved coating system

Name the selected product system or provide clear performance criteria and an approval process for alternatives. The submission should include applicable test and assessment evidence and the manufacturer's loading data for the members involved.

Specify the complete system rather than the intumescent layer alone:

• Surface preparation requirements
• Primer product, condition and permitted thickness range
• Intumescent product and project-specific loading schedule
• Compatible topcoat where required
• Environmental exposure during construction and in service
• Repair procedure for damage or out-of-tolerance areas

Any proposed substitution should be checked against the project design and confirmed by the coating manufacturer before use.

Set application and inspection requirements

The specification should define application conditions, hold points, measurement methods, acceptance criteria and responsibility for sign-off. It should also state the records required at handover.

Depending on the project, the record set may include substrate and primer checks, environmental readings, batch information, wet-film readings, dry-film measurements, marked-up drawings, photographs, repair records and independent inspection reports.

The exact inspection regime should follow the selected system's documentation and the contract requirements. Generic measurements or assumptions should not replace manufacturer and project-specific criteria.

Include site and programme information

Access, ventilation, masking, adjacent trades, weather exposure, curing periods and the sequence of follow-on work can affect quality and programme. Identify who provides access and protection, when areas will be released and how damage by later trades will be managed.

Make responsibilities explicit

State who is responsible for the fire strategy, structural design, section-factor schedule, product selection, loading schedule, substrate acceptance, application, inspection and final approval. This prevents design gaps from being passed informally to the applicator.

The Association for Specialist Fire Protection technical library includes industry guidance for the specification, installation and inspection of intumescent coatings.

Requesting an application quotation

Newlook Protective Coatings can review the practical application scope and quote for preparation and on-site intumescent coating when the design basis, steel information, selected system and quality requirements are available.

Newlook does not replace the fire engineer, structural engineer or coating manufacturer. If design information is incomplete, it should be resolved by the responsible project team before the coating build and firm application scope are confirmed.

To send the relevant project documents and request a quote, visit Newlook's Intumescent Coatings service.