Structural steel fireproofing is one of those elements of commercial building design that is mandatory, technically well-established, and yet frequently under-specified or poorly co-ordinated on Irish construction projects. The consequences of getting it wrong range from building control delays at completion to costly remedial work on site, and in the worst cases to fire protection installations that do not achieve the required fire resistance period despite appearing complete.
This article is written specifically for architects and structural engineers who specify structural steel fireproofing on commercial construction projects in Ireland and Northern Ireland. It covers the specification process, the choice between spray-applied and intumescent systems, the information required to specify correctly, the procurement and programme considerations that affect how the fireproofing element of a project runs, and the documentation that must be in place for building control sign-off.
FireShield Ireland carries out structural steel fireproofing on commercial construction projects across all 32 counties of Ireland and throughout Northern Ireland, using both Monokote spray applied fireproofing and intumescent coating systems. As the only licensed Monokote applicator in Ireland, we are the primary contact for spray-applied fireproofing on Irish construction projects. Full details of our structural steel fireproofing service are at https://fireshieldireland.com/services/structural-steel-fireproofing/.
The Specification Decision: What the Regulations Require
The starting point for specifying structural steel fireproofing on any Irish commercial project is the fire resistance requirement for elements of structure. In the Republic of Ireland this is determined by reference to Technical Guidance Document B, Fire Safety, which gives the required fire resistance period in minutes for different purpose groups and building heights. In Northern Ireland the equivalent reference is Technical Booklet E.
The required fire resistance period is an outcome requirement. It specifies what the structural element must achieve, specifically the period in minutes for which it must maintain its load-bearing capacity, integrity, and insulation under standard fire exposure conditions. It does not specify how that outcome is to be achieved. The choice of fireproofing system is a design decision made by the specifier within the constraints set by the required fire resistance period, the structural section sizes, and the other project-specific requirements that affect system selection.
Getting the required fire resistance period right for each element of structure on the project is the essential first step in the specification process. Errors in the required fire resistance period, whether specifying too short a period and failing to comply with the regulations, or unnecessarily specifying a longer period than required and incurring unnecessary cost, both cause problems later in the project. The required period for each structural element should be clearly established at design stage and confirmed with the fire authority or building control officer where there is any ambiguity.
System Selection: Spray-Applied Fireproofing vs Intumescent Coatings
The two main structural steel fireproofing systems used on Irish commercial construction projects are spray-applied cementitious fireproofing, of which Monokote is the principal product specified in Ireland, and thin film intumescent coatings. Each system has characteristics that make it more appropriate in different situations, and many projects use both systems in different areas of the building.
The fundamental criterion for system selection is whether the structural steel is concealed or exposed in the finished building. This is not simply a matter of whether the steel will be seen by building occupants. It is a question of whether the fire protection system needs to provide an acceptable surface finish as well as fire resistance performance.
For concealed steelwork, above suspended ceilings, within service voids, or in areas not accessible to building occupants, Monokote spray applied fireproofing is the appropriate and cost-effective choice in the majority of cases. Monokote does not provide a surface finish quality suitable for architectural applications. It has a characteristic rough, textured appearance that is entirely acceptable in concealed locations but would not meet the visual quality requirements of an occupied space or a publicly visible area of the building.
For exposed and architectural steelwork, where the structural steel is visible in the finished building and forms part of the architectural design, thin film intumescent coatings are the standard specification. Applied at the required dry film thickness and finished with a topcoat in the specified colour, an intumescent coating provides a surface finish comparable to a conventional paint that is appropriate for reception areas, atria, open-plan office floors with expressed structure, retail spaces, sports facilities, and all other architectural applications.
Where a building has both concealed and exposed structural steel, which is the case on most significant commercial projects in Ireland, the specification should identify clearly which system applies to which elements and what the interface conditions are between the two systems.
What the Specifier Needs to Provide
Specifying structural steel fireproofing correctly requires specific information about the structure. Without this information the fire protection contractor cannot confirm that their system achieves the required fire resistance period for the specific structural members on the project, cannot produce the project-specific thickness schedule required for the installation, and cannot provide the documentation required for building control sign-off.
The information required for spray-applied fireproofing specification includes the structural section designations and weights for all members requiring fire protection, the required fire resistance period for each element or group of elements, the primer specification for the structural steelwork, the ambient conditions in which the fireproofing will be applied, and any project-specific requirements for the application programme or phasing.
For intumescent coating specification the same structural information is required, plus the specified colour and finish for the coating, the required surface preparation standard, whether the topcoat is to be applied by the intumescent coating contractor or by a separate decorative contractor, and any specific quality or inspection requirements for the coating application.
The earlier in the design process this information is available, the earlier the fire protection contractor can confirm the specification, raise any technical questions, and provide reliable pricing. Waiting until the tender documents are complete before engaging the fire protection contractor is a common approach on Irish projects but it introduces a risk of specification errors or incompatibilities that are identified after the contract is awarded rather than during the design process when they are easier and cheaper to resolve.
NBS Specification for Structural Steel Fireproofing
The National Building Specification is the standard specification system used by architects and engineers on Irish and UK construction projects. Structural steel fireproofing is specified under NBS work section Z22, which covers protective coatings.
An NBS clause for Monokote spray applied fireproofing should reference the specific Monokote product grade, require application in accordance with the manufacturer’s current application specification and the relevant industry application standards, specify the minimum applied thickness for each structural section type or cross-reference a project-specific thickness schedule, require quality control procedures including thickness and density verification in accordance with the manufacturer’s requirements, and require comprehensive completion documentation including fire resistance calculations, installation records, and a completion certificate.
An NBS clause for thin film intumescent coatings should specify the product system by manufacturer and product reference, the required surface preparation standard, the compatible primer system, the required dry film thickness for each structural section type or cross-reference a project-specific thickness schedule, the specified colour and finish for the topcoat, the quality control and inspection requirements, and the documentation required at completion.
We provide NBS clause content for both Monokote and intumescent coating specifications on request and are available to advise on specification content at any stage of the design process.
The Structural Engineer’s Role in Fireproofing Specification
The structural engineer has a critical role in the fireproofing specification that goes beyond simply identifying the required fire resistance period. The structural information provided by the structural engineer is the basis for the thickness calculations that determine how much fireproofing is applied to each structural member on the project.
The section factor, which is the ratio of the heated perimeter of the structural section to its cross-sectional area, is the primary variable in the thickness calculation for both spray-applied and intumescent systems. The section factor varies significantly between different structural section sizes and between different exposure conditions. An exposed universal beam with four faces exposed to fire has a different section factor from the same beam spanning between floors with its top flange embedded in a concrete deck and only three faces exposed.
Providing the fire protection contractor with accurate structural information, including section designations, weights, and exposure conditions, early in the design process allows the thickness calculations to be carried out accurately and the project-specific thickness schedule to be prepared before the specification is finalised. This avoids the situation where the thickness schedule is prepared after the tender and reveals that the specified thickness in the specification documents is incorrect for some of the section sizes on the project.
Where the structural engineer carries out a fire engineering calculation to demonstrate that a reduced fire resistance period can be assumed for some structural elements based on their load ratio, this information must be communicated to the fire protection contractor clearly. The load ratio affects the required thickness of both spray-applied and intumescent systems and must be correctly incorporated into the thickness calculations.
Programme Implications for Specifiers
The fireproofing programme is frequently underestimated on Irish commercial construction projects. Understanding the programme implications of structural steel fireproofing at the design stage helps specifiers and project managers ensure that adequate time is allowed in the construction programme.
For spray-applied fireproofing with Monokote, the key programme activities are the confirmation of the primer compatibility, the mobilisation of the application team and equipment to site, the application itself with the required coverage rate, the thickness and density verification after application, and the drying period before follow-on trades can work in the fireproofed area. The application rate for Monokote depends on the thickness required and the complexity of the steelwork geometry. Simple column and beam grids in regular open areas can be applied relatively quickly. Complex connection details, haunched beam ends, and areas with restricted access take longer.
For intumescent coatings the key programme activities are the surface preparation, which for architectural work to the required standard involves blast cleaning and careful preparation of the steel before leaving the fabrication shop, the primer application, the intumescent application in one or more coats with the required drying intervals, the topcoat application, and any final inspection and touch-up work. Intumescent coating applied in the fabrication shop and then transported to site requires careful handling to avoid damage to the coating during transportation and erection, and any damage must be repaired on site before the coating can be signed off.
The interface between the fireproofing programme and the ceiling installation, mechanical and electrical first fix, and other follow-on trades must be managed carefully. In particular, the ceiling installation cannot proceed in any area until the fireproofing has been completed and verified, because once the ceiling is installed access to the steel for verification or remedial work is no longer possible without removing the ceiling.
Design Co-ordination: Common Issues
Several recurring co-ordination issues between the fireproofing specification and other design elements arise on Irish commercial projects and are worth addressing at the design stage rather than on site.
Steel Fabricator Primer Compatibility
Steel fabricator primer compatibility is one of the most common issues. The steel fabricator applies a shop primer to the structural steel at the fabrication stage for corrosion protection during transportation and storage on site. The primer specified by the structural engineer or steel fabricator must be compatible with the fireproofing system. Not all primers are compatible with Monokote and not all primers are compatible with all intumescent systems. If the primer is not confirmed as compatible before the fabricator applies it, the result can be the need to remove and replace the primer on site at significant cost and programme impact. The primer specification should be confirmed with FireShield Ireland at the earliest stage of the project, ideally before the fabricator is briefed.
Interface Between Monokote and Intumescent Coatings
On projects with both concealed and exposed steelwork, the interface between the two systems must be detailed. The interface typically occurs at the point where a structural element transitions from a concealed location above a suspended ceiling to an exposed location below the ceiling line. The specification must address this interface, confirming which system terminates at what point and how the joint between the two systems is detailed and finished.
Fire Protection of Steelwork Connections and Fittings
Fire protection of steelwork connections and fittings is frequently overlooked in the specification. Bolted connections, gusset plates, stiffeners, and moment connection plates are all structural elements that must be fireproofed to the same standard as the main members. These complex geometrical areas are harder to coat than straight beam and column sections and require specific attention in the specification and on site.
Documentation for Building Control: What the Specifier Should Require
The specification for structural steel fireproofing should include a clear requirement for the documentation to be provided at the completion of the installation. This documentation is required for building control sign-off and for inclusion in the building’s health and safety file and operation and maintenance manual.
The minimum documentation that should be required from the fire protection contractor includes the product data sheets and technical certificates for the fireproofing product applied, the fire resistance calculations demonstrating that the applied system and thickness achieves the required fire resistance period for each structural section type on the project, the project-specific thickness schedule showing the required thickness for each section type, the quality control records from the installation showing thickness and density measurements in accordance with the manufacturer’s requirements, a record of any remedial work carried out and the re-verification measurements confirming the remedied areas meet the specification, and a completion certificate signed by the fire protection contractor confirming the installation complies with the specification.
FireShield Ireland provides all of this documentation as standard on every project, prepared in a format suitable for submission to local authority building control authorities in both the Republic of Ireland and Northern Ireland. We are available to liaise directly with building control officers and to attend site inspections where required.
Engaging FireShield Ireland at the Specification Stage
The most effective way to ensure that the structural steel fireproofing on a commercial project in Ireland is correctly specified, efficiently procured, and properly documented is to engage FireShield Ireland at the specification stage rather than at the tender or construction stage.
At the specification stage we can confirm the appropriate system for each area of the project, provide the project-specific thickness schedule based on the structural information available, confirm primer compatibility with the steel fabricator’s specification, provide NBS clause content for the specification documents, and give preliminary pricing and programme estimates for inclusion in the project cost plan and programme.
This early engagement costs nothing and provides significant value to the design team and the project programme. Contact us to discuss any commercial project in Ireland or Northern Ireland at any stage of the design process.
https://fireshieldireland.com/services/structural-steel-fireproofing/
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