Specifying Fire Resistive Coatings

Specifying Fire Resistive CoatingsPresented by:

Jayson L. Helsel, P.E.KTA-Tator, Inc.

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Learning ObjectivesComprehension of the webinar will enable the participant to:

•Describe how intumescent coatings protect underlying steel from heat exposure

•List two fire rating classification tests that are used to qualify intumescent coatings for use in building construction

•Identify two primary resin types that are used to formulate intumescent coatings

•Explain how steel size and structure design affect specified thickness and number of coats

Fire Resistive Coatings

• Sprayed Fire Resistive Materials (SFRM) are broad group of materials including:– Cementitious and gypsum based

materials– Intumescent coatings

(Note: There is a separate category for “Fire Retardent” coatings, which are not reviewed here)

Fire Resistive Coatings

• Intumescent Coatings:– Are categorized as SFRMs– Similar to conventional coatings – Have unique fire resistant properties

Intumescent Coatings

• How they function: – Intumescent coatings char and swell

when exposed to fire/heat– The charred layer acts to insulate the

steel from fire

Intumescent Coatings

• Performance ratings– Coatings rated by how long steel is

protected at specified thickness– Ratings from 1 to 3 hours (at 30

minute intervals– Specific to shape/size of steel,

e.g. W10 x 49 column

Fire Resistance Classifications

• Underwriters Laboratories (UL) is recognized authority that evaluates and approves intumescent coatings for a certain classification and fire rating

• Certifications can be verified online at www.ul.com


• Certifications are “design” specific by coating manufacturer

• Numbering system defines an alphanumeric design number


• Beams– W, M or S shaped steel sections (AISC)– Minimum beam size for fire resistance is

expressed as W/D ratio• W = weight of beam per lineal foot• D = perimeter of protection material

– Beams of same configuration with greater W/D ratio may be used in design


• Columns– Minimum column size and configuration

specified in X and Y series designs– Same hourly rating applies when section

with equal or greater W/D ratio is substituted for same configuration


• Beams and Columns– Required coating thickness increases as

weight of steel decreases• Lighter steel heats up more rapidly and

requires more protection


• ANSI/UL 263– Used for resistance to cellulosic fire (e.g.

combustion of wood or building materials)

– Slower rise in temperature• 1000 F at 5 min.; 1550 F at 30 min.; 1700 F

at 60 min.; 1925 F at 180 min.; 2000 F at 240 min.

– Interior and exterior exposures


• ANSI/UL 263 Classified Coatings– Typical use for structural steel in

commercial structures


• ANSI/UL 1709– Used for resistance to a hydrocarbon fire– Rapid rise in temperature

• 2000 F at 5 minutes – Interior and exterior exposures

• Environmental tests include, accelerated aging, high humidity, salt spray, thermal cycling for exterior exposure


• ANSI/UL 1709 Classified Coatings– Typical use for steel structures at

petrochemical facilities, e.g.• Chemical plant• Refineries• Offshore oil platforms

Other Approvals• Intumescent coatings may also need

approval by city building codes• Coating manufacturers should

provide approvals as applicable

Generic Coating Types• Intumescent coatings are generally

the following generic resin types:– Acrylic/vinyl– Epoxy

• Intumescents are also generally categorized as “thin-film” or “thick-film” coatings

Generic Coating Types• Acrylic/vinyl

• Thin-film coating• Solvent or water-based• Single component • Typically rated under UL 263

Generic Coating Types• Acrylic/vinyl

• Applied in several coats• Time-frame for a complete application may

span several days• Additional time may be needed before

application of any required exterior finish coat.

Generic Coating Types• Epoxy

• Thick-film coating• Applied by plural component spray

equipment in one or two coats• Rapid cure• Typically rated under UL 1709

Generic Coating Types• Epoxy

• May require mesh reinforcement (e.g. metal, fiberglass, carbon)

• Typically requires the use of applicators licensed or approved by the coating manufacturer

Generic Coating ComparisonCoating

TypeRequired Thickness

(mils)

Number of Coats

Recoat Time (between

coats) @50F

Time to Finish Coat

@50FSolvent based acrylic

130 5 24 hours 25 days

Solvent based vinyl

375 4 4 hours 20+ days

Water based acrylic

180 6 8 hours 10+ days

Epoxy 180 1 n/a 24 hours

Epoxy w/mesh

340 1-2 n/a 48 hours

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Testing for Coating Cure• Intumescents may require testing for

proper cure• Typical test is Durometer Hardness

(Shore D)– Resistance of coating film to indentation

by Durometer instrument– ASTM D2240, “Standard Test Method for

Rubber Property-Durometer Hardness”

Testing for Coating Cure

Coating Appearance• Intumescents generally have a rough

or orange peel appearance• Methods to improve include:

• Back rolling following spray application• Sanding (not recommended)• Finish coat application (may be required)

• Test sections recommended

Coating Systems• Intumescent design approvals

typically include a primer and/or finish coat– When included in design primer/finish

must be applied to meet fire rating• Primer/finish must be endorsed by

intumescent coating manufacturer– Preference always for same

manufacturer

Use of Primers• Intumescent coating manufacturer

may have approved list of primers– Types include alkyd, acrylic, epoxy and

zinc-rich– Application thickness important

Primers• Function of primer

– Provides adhesion to substrate – Provides suitable surface for

intumescent– Provides additional barrier protection

• Can also provide inhibitive or sacrificial protection

Use of Finish Coat• May be required in design approval

for exterior exposure• Intumescent coating manufacturer

must endorse finish material– Types include 100% acrylic and aliphatic

urethane coatings• May affect/improve appearance

Finish Coats• Function of topcoat

– Color and gloss– Abrasion resistance– Chemical resistance– Washability– Resistance to the environment

Finish Coats• Acrylics

– Advantages• Single component• Ease of application• Color & gloss retention• Flexibility• Low VOC content for waterbased

Finish Coats• Acrylics

– Limitations• Limited alkali and solvent resistance• Moderate abrasion resistance• Application temperature >50ºF for

waterbased

Finish Coats• Urethanes

– Advantages• Color & gloss retention (aliphatic)• Adhesion• Acid, alkali resistant• Chemical resistant• Impact/abrasion resistant

Finish Coats• Urethanes

– Limitations• Multi-component• Short recoat intervals• Limited pot life• Moisture sensitive during cure• Difficult to recoat

Fire Resistive Coating Inspection

• Technical Manual 12-B– Published by Association of the Wall and

Ceiling Industries (AWCI International)– Individual measurement = average of 3

gauge readings (similar to SSPC-PA 2)– Testing frequency one bay per floor or

one test per 10,000 square feet (further defines required shapes)

Fire Resistive Coating Inspection• Technical Manual 12-B

– Scope– General Information– Substrate Conditions– Site Conditions– Inspection Procedures– Method of Tests– Conditions of Finished Application– Patching

Fire Resistive Coating Inspection

• Intumescent (and Mastic) Coatings– Coating thickness specification in a

design is minimum average thickness measured in accordance with Technical Manual 12-B• Average thickness should not exceed

maximum thickness published (if listed) in individual designs

• No individual measurement <80% of specified design thickness

Summary of Key Points• When specifying intumescents

consider:– Required UL approval– City building code approval– Include required primer and finish coats– Applicator certification if needed (e.g.

plural component materials)– Include test sections to evaluate

appearance

Specifying Fire Resistive Coatings

• Questions?

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Specifying Fire Resistive Coatings