Standardizing guidelines to specify IFRMs

by arslan_ahmed | October 16, 2023 6:00 am

[1]

By Max Tritremmel

Architecturally exposed structural steel (AESS) (Figure 1) is a popular design feature that can complement the strength and beauty of steel to other architectural features. However, as a key part of what provides the integrity of the structure, that steel must be protected to ensure it retains its strength in the event of a catastrophic fire.

Traditional fire protection materials were sprayed fire-resistive materials (SFRMs), commonly referred to as cementitious fire protection (CFM), which were not well-suited to complement the beauty of exposed steel. The unsightly finishes often required concealment in the form of drop ceilings, sheetrock, or covers to ensure architects could meet their aesthetic design objectives. The material is also messy when left uncovered, contributing to a large amount of dust in spaces that creates a constant cleaning nuisance, and can quickly clog HVAC filters.

The advent of intumescent fire-resistive materials (IFRMs), which are smooth in appearance, finally allowed for the expression of exposed steel in new and creative ways, and new material innovations continue to support this change. IFRMs allow designers to strip away the unnecessary elements that were common in construction in the last century and create new, simpler buildings—delivered with greater speed, total cost efficiency, and sleeker appearances.

Given the emphasis on beauty with AESS, it is to be noted, no single global standard exists for specifying the finish appearance of the IFRM coating for this element in building design. The American Institute of Steel Construction (AISC) offers a detailed category system for specifying the overall finish quality of exposed steel, based on member visibility, viewing distance, location, lighting, coatings, style, adjacency, and cost.¹ However, the AISC guidelines make only minimal reference to IFRM coatings in the AESS category system, generally referring to these coatings as “smooth.” Establishing better guidance for the appearance of IFRMs on exposed structural steel will help the construction and coatings industries deliver better outcomes for AESS.

[2]

Current IFRM finish standards

Historically, the fire protection industry has concerned itself with performance defined by code compliance, rather than the finish. Architects and contractors bear the shared responsibility for the look and finish quality of AESS surfaces, as well as compliance with those codes. In the absence of a defined coating standard for the appearance of IFRMs applied to AESS, they have no real objective or straightforward way to define the look of an AESS finish in advance for the building owner to approve.

[3]

With no overarching standard to reference, some architects initially turned to makeshift standards, such as the GA-214-2021, Levels of Finish for Gypsum Panel Products guidelines.² It made sense when considering the adjacent role of gypsum wallboard in fire containment and the interaction of it in wall systems when attaching to and encasing SFRMs. While GA-214-2021 may provide a useful analogue for finish quality; the materials, processes, and tools used to apply gypsum-based products are quite different from those used with IFRMs applied to exposed steel surfaces and, ultimately, the correlation was poor with the desired outcomes often being off the mark.

An important reason is, it is not aligned with AESS and does not take observer distance into account to differentiate between the levels. Further, the references to tape and the number of coats of compound make differentiating between GA-214 Levels 2 and 4 difficult for IFRMs as the addition of more coats would not necessarily ameliorate appearance in the case of IFRMs. Lastly, the premium Level 5 finish requires a skim coat of a differentiated material, something which is not permitted in the fire protection world without a corresponding fire test with the topping material.

In Europe, where IFRMs have surpassed SFRMs in cellulosic fire protection applications, the guidance is a bit more advanced and closer to the mark. The Association for Specialist Fire Protection (ASFP) Technical Guidance Document 16 (TGD 16), Code of Practice for Off-Site Applied Thin Film Intumescent Coatings,³ outlines three categories of finishes—basic, decorative, and bespoke—and promotes cost-saving, off-site IFRM applications so pre-coated beams arrive at the jobsite ready for assembly.

This ASFP standard is a dramatic improvement over the use of the AWCI/GA 214 standard. It is built to cater to IFRMs, including application variations such as orange peel. It also considers observer distance, which will be critical to identify when the use of the standard is appropriate. However, the use of this standard is problematic for several reasons.

The AESS standard describes five specific levels of finish—with each dramatically increasing in cost and the last one being a custom finish—whereas TGD 16 outlines three levels. The first two levels line up well with Level 1 and Level 2 for AESS, but would leave Levels 3, 4, and custom all in extreme variation of the “bespoke” category.

In AESS, the biggest increase according to the cost matrix comes between Levels 3 and 4; much more so than between Levels 1 and 2; and this would be equally the case when determining the variation between appearing smooth from less than 5 m (16 ft) away—the only observer distance referenced in the decorative finish guidelines in TGD 16—or being actually smooth, which is the expectation of AESS Level 4. These discrepancies in the finer points of the “bespoke” category would likely further lead to less predictability in estimating within this category.

[4]

In addition, the description of a “decorative finish” in the second paragraph of the ASFP guidance document is largely subjective and may lead to dispute on cost impact and remedial work to achieve a “good standard of cosmetic finish.” The standard would also rely on the bespoke finish for all critical items in close view (AESS categories 3 and 4). Commercially, this is an issue for hard bid work, as the concept of a bespoke finish agreed in the field lends itself more to design build arrangements due to its inherent ambiguity. A contractor may have an issue providing an effective bid for an item for which its level of effort would likely be determined post-award.

In the absence of an objective, industry-accepted standard, coatings manufacturers, applicators, architects, and building owners continue to struggle with all the basic characteristics—material selection, application and finishing procedures, appearance standards, and more. Further, with no allegiance to a single standard, there remains considerable room for subjectivity, bias, and costly disagreement over the finish quality of coated AESS members. Ideally, an appearance standard for IFRM coatings would be built to align with the AISC’s AESS categories and their specific surface quality requirements.

IFRM materials, formulation, application, and finishing criteria

Any workable global IFRM finish standard for AESS must address the three generic types of IFRM coating materials: water-based acrylic, solvent-based acrylic, and plural-component intumescent materials. The comparisons found in Table 1 and 2 highlight key features of these material types and suggest how material capability, formulation, application, dry time, and service environment influence material selection and finish. In general:

• Both water- and solvent-based acrylic intumescent systems are applied in thinner coats than epoxies—typically 30- to 60-mil dry film thickness (DFT)—making them likely to self-level into smoother finishes. In addition, their lower viscosity enables the use of finer spray tips, resulting in better atomization and a more aesthetic finish. Acrylic intumescent materials are typically well suited for interior, general-purpose, and conditioned spaces. These materials may also be used on some exteriors with the help of a topcoat to protect the fire protection coating from atmospheric degradation.
• Epoxy intumescent materials are applied in thicker films, typically around 100-mil DFT or more, but their thixotropic nature makes for a more textured or “orange-peeled” finish. Epoxies provide the best overall long-term performance, especially in corrosive, physically demanding, or severe exterior environments, giving them a substantial life-cycle cost advantage over acrylics in these applications. They also lend themselves to off-site application, making them ideal for new construction projects, particularly for AESS-2 designs.

[5]

While performance requirements and material composition are strong influencers on IFRM coating finishes, three other issues can also play a vital role in the finish quality of IFRMs, including: product formulation, application techniques, and secondary shaping, such as sanding and using rasps. The level of finishing, such as troweling and finish rolling, affect the finish quality as well, along with DFT requirements, as coatings with higher DFTs tend to be rougher and or wavy in appearance.

[6]

Formulation

Finish-related factors in formulation include variables such as fiber content and length, pigment selection and concentration, and the use of thixotropic thickeners or other additives essential for fire-retardance, film build, or other properties. Often, IFRM formulations will need to strike a balance between aesthetics and performance.

More viscous materials will apply in thicker film layers and therefore require fewer application steps, but those films may be more textured in appearance. These high-solids epoxy formulations feature diluents that react and are retained within the final cured coating, allowing for thicker builds. Conversely, acrylics must be applied in multiple thinner coats to allow for diluent evaporation.

Fiber selection and content can also have a significant impact on final appearance. For example, long-strand fibers can improve the strength of the char in a fire test and extend the coating’s insulating time at lower film thicknesses. However, the added fiber content creates texture in the finish, forcing building specifiers to trade the improved performance for some reduced aesthetic appeal.

The key takeaway here is, formulation that may be necessary for performance, may be detrimental for appearance. Oftentimes, it is critical to understand this, as functionally higher performing materials may prove more difficult when achieving the desired performance.

Application

Methods for applying IFRMs include spraying, brushing, rolling (typically for touching up small areas only), or troweling, with the final appearance
of the coating dependent on both, the material’s characteristics, and the skill of the applicator.

Spray applications generally provide the best initial appearance, though the quality of the finish can vary based on the type of equipment used, the film thickness applied, the amount of solvent reduction, spray pressure, and the spray distance to the substrate (Figure 3). Key equipment considerations include using the proper hose diameter, spray gun, and tip size, all of which can affect material flow, atomization, and final appearance.

[7]

Both material and surface temperature are also critical application factors. Materials applied at higher temperatures or to warmer substrates generally build lower films and flow slightly better for a smoother finish due to the higher temperatures mildly reducing the coatings’ viscosity. However, too high temperature may result in accelerated “tacking up” of the coating, which will not allow it to level out. Conversely, at lower temperatures, applicators can increase film builds, but the film appearance may be slightly rougher. The material flow is also reduced at lower application temperatures, reducing efficiency.

Applicator spray distance from the target is a third critical factor; it requires a balance between film texture, which improves at greater spray distances, and film waste, which also increases with distance. Further, an applicator who is too close to a target can “push” material with the force of the spray stream and create wavy patterns in the final film. An applicator who is too far from the surface or applies coatings at an acute angle can leave a splattered finish, leading to excessive waste.

Secondary procedures

To improve the shape and finish of applied coatings, applicators may perform secondary procedures, such as trowel finishing, finish rolling, rasping, sanding,
or grinding. However, the success of any of these procedures depends on timing, particularly when epoxy IFRMs are involved.

Finish rolling freshly applied sprayed intumescent coatings reduce the initial texture of epoxies and can make them appear smoother from a distance. Rolling must be done at the right time after the initial application—early, but not too early—in the cure. Rolling too early can “push” the material, creating thickness variations and an uneven film build appearance. It can also result in the material sticking to the roller cover, creating a stippled finish. Rolling too late will not smooth the finish at all. Misting, not soaking, the roller cover with solvent may help in finish rolling, provided the solvent can be used in the work environment. It must be noted, using excessive solvent can extend the recoat or dry time of the material or lead to solvent entrapment should it be overcoated too soon.

Rasping can smooth out runs, sags, spits, or other textural defects. However, it must be performed during an intermediate stage of curing, when the material is firm enough to withstand a rasping treatment without deforming, but not so late that rasping is ineffective. Certain well-cured epoxy coatings rasp very well. To facilitate timely coating applications, rasping may need to be done on a follow-up shift, which requires costly additional labor.

Abrasive methods such as sanding or grinding can achieve the smoothest IFRM coating finishes. However, they are far more costly, since they require added labor, and over-application of the coating (around 20 percent), some of it can be removed to create a smoother protective coat while retaining the minimum specified thickness for the structure’s rated fire protection. Adding to the complexity, abrasive processes can be more difficult to manage. Acrylic coatings may heat up and soften, causing abrasives to gum up quickly, while epoxy formulations naturally resist abrasion and surface damage. Optimizing overall cost may require modifying application procedures and using rolling and rasping to reduce the need for abrasive methods.

A proposal for the future

With the proliferation of AESS being used in today’s building designs and the variation and cost associated with meeting finish levels that complement the AESS standard for IFRM materials, new standards should be developed to facilitate the growth of this sector of the coatings industry. This standard should consider both, the AISC AESS standard and the formulation, application, as well as the finishing requirements of the IFRM materials required for fire protection.

Alignment of a new global IFRM finish standard with current AISC AESS standards is essential for several reasons, and could be accomplished through a series of connected endeavors:

• First, the appearance quality of the IFRM coating depends substantially on the specified quality of the AESS. Therefore, standards for IFRM finish quality should be created to align with and complement the steel quality standard. For example, since IFRMs will mirror any defects in the underlying steel, high-quality finishes cannot be achieved on a lower quality steel member.
• A secondary project could be undertaken to evaluate the relative cost of modifying each coating material type to meet requirements for a series of standard finishes. This way, reasonable cost estimates could be established to help with project budgeting and bid validation to mitigate disputes and improve results in field projects. The exception to these rules would be any custom finishes.
• A tertiary project could include standardizing best practice application techniques into an applicator training and certification program, which could be used to qualify applicators.

Taken together, efforts that would produce a new global IFRM finish standard could dramatically improve the accuracy of project proposals involving protected AESS by offering specifiers a more objective mechanism for aligning performance, finish, and cost expectations with the most appropriate materials and well-trained applicators. At the same time, a new IFRM coating finish standard would help to drive the growth of the fire protection coatings industry, while offering architects and owners new options for safe and visually appealing building designs and more consistent outcomes.

A new standard such as this would play a role in minimizing project and material costs, eliminating the need for decorative or covering elements, such as column covers and drop ceilings, and create more beautiful, greener, and more economical structures in the future.

References

¹ See the Code of Standard Practice for Steel Buildings and Bridges, Section 10: Architecturally Exposed Structural Steel p. 65-66 (June 15, 2016), American Institute of Steel Construction (AISC), 130 East Randolph Street, Suite 2000, Chicago IL, 60601.

² See GA-214-2021, Levels of Finish for Gypsum Panel Products (September 30, 2021), Gypsum Association, 962 Wayne Ave., Suite 620, Silver Spring, MD 20910.

³ Refer to the Technical Guide Document 16 (TGD 16), Code of Practice for Off-Site Applied Thin Film Intumescent Coatings (Second Edition), Association for Specialist Fire Protection (ASFP), Spectra House, Westwood Way, Westwood Business Park, Coventry CV4 8HS, U.K.

Author

Max Tritremmel is fire protection market segment director—Americas, for Sherwin-Williams Protective & Marine. For more than 26 years, he has served the coatings industry as a sales representative, business leader, industrial painting contractor, and now marketer. Tritremmel is a Society for Protective Coatings (SSPC) protective coatings specialist, and an SSPC level three certified coatings inspector. He can be reached via email at Max.Tritremmel@sherwin.com.

Source URL: https://www.constructionspecifier.com/standardizing-guidelines-to-specify-ifrms/

---