Fire safety is non-negotiable in commercial construction. Spray polyurethane foam (SPF) is a combustible plastic material, and building codes impose strict requirements on how and where it can be installed. Understanding ASTM E84 (surface burning characteristics), ASTM E119 (fire-resistance ratings), and UL assembly listings is essential for spec compliance and passing inspections.

Here’s what you need to know about spray foam fire ratings, code requirements by occupancy, and when you need intumescent coatings or thermal barriers.

ASTM E84: Surface Burning Characteristics (Steiner Tunnel Test)

ASTM E84 is the primary test method for evaluating the flame spread index (FSI) and smoke-developed index (SDI) of building materials, including spray foam insulation.

What the Test Measures

A 25-foot-long sample of the material is placed in a horizontal tunnel furnace and exposed to a controlled flame for 10 minutes. Sensors measure:
– Flame Spread Index (FSI): How quickly flame propagates across the surface (scale: 0-100+)
– Smoke Developed Index (SDI): Density and obscuration of smoke produced (scale: 0-450+)

The material is compared to two reference standards:
– Red oak lumber: Assigned FSI = 100
– Cement board: Assigned FSI = 0

Fire Rating Classes

Based on FSI and SDI, materials are classified as:

Class Flame Spread Index (FSI) Smoke Developed Index (SDI) Common Materials
Class 1 (Class A) 0-25 0-450 Gypsum, cement board, mineral wool, some spray foams
Class 2 (Class B) 26-75 0-450 Treated plywood, some rigid foam boards
Class 3 (Class C) 76-200 0-450 Untreated wood, some insulation materials

Most building codes require Class 1 (Class A) spray foam for most commercial and residential applications. Class 2 is acceptable in limited cases (see below).

Do All Spray Foams Meet Class 1?

Closed cell spray foam: Most closed cell polyurethane foams are formulated with flame retardants and can achieve Class 1 (FSI <25) when tested per ASTM E84. Typical results:
– FSI: 15-25
– SDI: 300-450

Open cell spray foam: Open cell foams generally have higher flame spread (FSI 20-35) and may fall into Class 1 or Class 2 depending on formulation and fire retardant content. Some low-density open cell foams require a thermal barrier or intumescent coating to meet Class 1.

Check the manufacturer’s ICC-ES Evaluation Report (ESR) or UL listing for your specific product’s ASTM E84 results. Do not assume all foams are Class 1.

ASTM E119: Fire-Resistance Ratings for Assemblies

ASTM E119 tests entire wall, floor, or ceiling assemblies (not just the insulation material) to determine how long they can resist fire exposure before structural failure or flame/heat transmission occurs.

What the Test Measures

A full-scale assembly is subjected to a standardized time-temperature curve (reaching 1,700°F in one hour, 2,000°F in four hours). The assembly is rated based on:
– Structural integrity: Does the assembly collapse?
– Flame transmission: Do flames penetrate to the unexposed side?
– Heat transmission: Does the unexposed side reach unsafe temperatures?

Ratings are expressed in hours: 1-hour, 2-hour, 3-hour, or 4-hour fire-resistance.

How Spray Foam Fits Into ASTM E119 Assemblies

Spray foam itself does not have an E119 rating—assemblies do. A 2-hour rated wall assembly might include:
– 2 layers of 5/8″ Type X gypsum board (each side)
– Steel studs at 16″ o.c.
– Closed cell spray foam cavity insulation
– Specific fastener schedule and joint treatment

The spray foam is one component of the assembly. The gypsum provides the fire resistance; the foam provides thermal and air barrier performance.

To meet fire-resistance requirements, use spray foam only in assemblies with published UL or Intertek test results.

UL Assembly Listings: Finding Code-Compliant Designs

The International Building Code (IBC) and International Residential Code (IRC) allow spray foam insulation in fire-rated assemblies only if the assembly has been tested and listed by an accredited lab (UL, Intertek, FM Global).

Where to Find UL Assembly Listings

Search by:
– Assembly type (wall, floor, ceiling)
– Fire-resistance rating (1-hour, 2-hour, etc.)
– Construction type (wood frame, steel stud, concrete)

Example: 2-Hour Fire-Rated Steel Stud Wall with Spray Foam

UL Design U425:
– 3-5/8″ 20-gauge steel studs at 24″ o.c.
– Two layers 5/8″ Type X gypsum board each side
– Closed cell spray foam in cavity (up to 3.5″)
– Screws per specific schedule
– Joints taped and finished

This assembly has been fire-tested and meets IBC 2-hour fire-resistance requirements. Substituting materials (different foam, thinner gypsum, wider stud spacing) voids the listing.

Always build exactly to the tested assembly specs. Do not improvise.

Class 1 vs Class 2: Code Requirements by Occupancy

The IBC and IRC have different requirements depending on occupancy type, building height, and whether the foam is exposed or covered.

When Class 1 (Class A) Is Required

IBC Section 2603.3:
– All spray foam insulation in commercial buildings must meet Class 1 (FSI ≤25) when:
– Installed in occupied spaces
– Not separated from the building interior by a thermal barrier (e.g., ½” gypsum)

IRC Section R316.3:
– Similar requirement for residential occupancies

If the spray foam will be left exposed (e.g., underside of roof deck in a warehouse, spray foam on basement walls without finish), it must be Class 1 and often requires a 15-minute thermal barrier or ignition barrier.

When Class 2 (Class B) May Be Acceptable

Class 2 spray foam (FSI 26-75) is allowed in limited cases:
– Covered by a thermal barrier: If spray foam is fully covered by ½” gypsum, ¼” plywood, or equivalent 15-minute thermal barrier, Class 2 may be permitted (check local code)
– Attics and crawl spaces: IRC R316.5.11 allows Class 2 foam in attics if entry is restricted to service access only (not habitable)

Safest practice: Specify Class 1 foam for all commercial applications to avoid code interpretation issues.

When Intumescent Coatings Are Required

Some spray foam products achieve Class 1 fire rating only when coated with an intumescent or fire-retardant coating. These coatings expand when exposed to heat, forming a protective char layer that insulates the foam and slows flame spread.

Intumescent Coating Applications

Typical scenarios:
– NFPA 285 compliance: Certain foam + cladding assemblies require intumescent coating to pass NFPA 285 vertical flame spread testing (see closed cell spray foam commercial for details)
– Exposed foam in occupied spaces: Warehouses, gymnasiums, or industrial buildings where foam is sprayed directly on underside of metal roof deck
– Class 2 foam upgrade: If you have Class 2 foam on-site and need Class 1 performance, intumescent coating can bridge the gap (verify with manufacturer)

Application Details

  • Coverage rate: 15-25 wet mils (depends on product)
  • Cost: $0.40 to $0.80 per sq ft material + labor
  • Dry time: 24-48 hours before foam can be exposed to traffic or finish work
  • Color: Typically white, gray, or red-orange (may require paint topcoat for aesthetics)

Common products:
– DC315 Intumescent Coating (Dow)
– ThermaSafe Fire Barrier Coating (BASF)
– FSI-201 (International Fireproof Technology)

Always apply per manufacturer’s coverage rate and thickness specs. Insufficient coating won’t deliver rated performance.

Code Requirements by Occupancy Type

Occupancy (IBC) Spray Foam Fire Rating Thermal Barrier Required? Notes
A (Assembly) Class 1 Yes (½” gypsum or 15-min equiv) Theaters, churches, lecture halls
B (Business) Class 1 Yes Offices, professional buildings
E (Educational) Class 1 Yes Schools, daycare (strict enforcement)
I (Institutional) Class 1 Yes (often 1-hour assembly) Hospitals, prisons (high life-safety)
M (Mercantile) Class 1 Yes Retail, malls
R (Residential) Class 1 Yes (IRC R316) Apartments, hotels, dorms
S (Storage) Class 1 Depends (may be waived for low-hazard) Warehouses, parking garages
U (Utility) Class 1 or 2 Often not required Sheds, agricultural buildings

High life-safety occupancies (I, E, A) face the strictest scrutiny. Inspectors will ask for:
– ASTM E84 test reports
– UL assembly listings
– Flame spread and smoke-developed certifications
– Intumescent coating certificates (if applicable)

Have this documentation on-site during inspections.

Spray Foam and Thermal Barriers

IBC Section 2603.4 requires a 15-minute thermal barrier between foam plastic insulation and the interior of the building, unless the foam has been tested as part of an assembly or meets specific ignition barrier criteria.

What Qualifies as a 15-Minute Thermal Barrier?

Common approved barriers:
– ½” gypsum wallboard (most common)
– ¼” plywood or OSB
– 3/8″ cement board
– 23/32″ T&G wood structural panels

These materials have been tested per NFPA 275 or equivalent and will resist heat transmission for at least 15 minutes, giving occupants time to evacuate before the foam is exposed to ignition temperatures.

Ignition Barrier (Lesser Standard)

For attics, crawl spaces, and areas not regularly occupied, an ignition barrier (lesser protection than thermal barrier) may be acceptable. Options:
– 1.5″ thick spray foam + intumescent coating
– Specific tested foam products listed for ignition barrier use

Check IRC R316.5 or IBC 2603.4.1.13 for prescriptive ignition barrier details.

Which Foams Pass Which Tests?

Not all spray foam products are created equal. Here’s a general breakdown:

Closed Cell Polyurethane Foam

  • ASTM E84: Most pass Class 1 (FSI 15-25, SDI 300-450)
  • NFPA 285: Select formulations pass when installed in approved assemblies
  • Thermal barrier: Required for occupied spaces per IBC/IRC
  • Fire-resistance assemblies: Widely used in UL-listed 1-hour and 2-hour designs

Open Cell Polyurethane Foam

  • ASTM E84: Typically Class 1 or Class 2 (FSI 20-40)
  • NFPA 285: Limited; not commonly used in combustible cladding assemblies
  • Thermal barrier: Required
  • Fire-resistance assemblies: Used in some residential assemblies; less common in commercial high-rating designs

Polyisocyanurate Rigid Foam (For Comparison)

  • ASTM E84: Class 1 with foil or fiber facing; uncoated may be Class 2-3
  • NFPA 285: Many formulations pass
  • Thermal barrier: Required unless part of tested assembly

Bottom line: Verify your specific product’s test data. Do not assume based on foam type.

Fire Rating Checklist for Spray Foam Projects

Before you spray, confirm:

  • [ ] ASTM E84 test report showing Class 1 (FSI ≤25) for your product
  • [ ] Thermal barrier specified (½” gypsum or equivalent) if foam is in occupied space
  • [ ] UL or Intertek assembly listing if fire-resistance rating required (1-hour, 2-hour, etc.)
  • [ ] NFPA 285 compliance verified if building >40 ft with combustible cladding
  • [ ] Intumescent coating spec’d and budgeted (if required)
  • [ ] Local AHJ (building official) approval of assembly design
  • [ ] On-site documentation ready for inspection (TDS, fire test reports, ICC-ES ESR)

Product CTA: Fire-Rated Spray Foam for Commercial Projects

R-Value Associates supplies closed cell spray foam formulations with Class 1 ASTM E84 fire ratings and full technical documentation for code compliance. Whether you’re bidding a UL-listed 2-hour assembly or need NFPA 285-compliant foam for a high-rise, we have:
– ICC-ES Evaluation Reports (ESR)
– ASTM E84 test results
– UL assembly design support
– Intumescent coating coordination (if needed)

Browse our 55-gallon drum options or contact us for project-specific specs.

Frequently Asked Questions

What is a Class 1 fire rating for spray foam?

Class 1 (also called Class A) means the spray foam has been tested per ASTM E84 and achieved a Flame Spread Index (FSI) of 25 or less and a Smoke Developed Index (SDI) of 450 or less. This is the highest fire safety classification for building materials and is required by the IBC and IRC for spray foam in most commercial and residential occupancies. Class 1 foam must still be covered by a thermal barrier (typically ½” gypsum) unless tested as part of an exposed assembly.

Does spray foam insulation meet fire code?

Yes, if the product has been tested per ASTM E84 and achieves at least Class 1 (FSI ≤25) and is installed with a 15-minute thermal barrier (½” gypsum or equivalent) as required by IBC Section 2603 and IRC Section R316. Spray foam used in fire-rated assemblies (1-hour, 2-hour walls/floors) must be part of a UL or Intertek-tested assembly. Always verify product test reports and assembly listings before installation.

What is ASTM E84 and why does it matter for spray foam?

ASTM E84 is the standard test method for measuring surface burning characteristics of building materials. It determines the Flame Spread Index (FSI) and Smoke Developed Index (SDI) by exposing a 25-foot sample to flame in a horizontal tunnel furnace. Building codes use E84 results to classify materials as Class 1, 2, or 3. For spray foam, Class 1 (FSI ≤25) is required in nearly all commercial and residential applications.

When is an intumescent coating required on spray foam?

Intumescent coatings are required when:
– The spray foam product achieves Class 1 fire rating only when coated (per manufacturer TDS)
– The assembly must pass NFPA 285 testing and the tested design includes intumescent coating
– Spray foam is exposed (not covered by gypsum) in an occupied space and local code requires additional fire protection
– You need to upgrade Class 2 foam to Class 1 performance

Always verify coating requirements in the product’s ICC-ES report or UL assembly listing.

Can I use spray foam in a 2-hour fire-rated wall?

Yes, if the complete wall assembly (studs, gypsum, foam, fasteners, joint treatment) has been tested and listed by UL, Intertek, or FM Global for 2-hour fire resistance per ASTM E119. The spray foam is one component of the assembly; it does not provide the fire rating on its own—the gypsum layers do. Use only the foam products and thicknesses specified in the tested assembly design. Substitutions void the listing and violate code.

Suggested Images:
1. Diagram showing ASTM E84 Steiner Tunnel test setup with labeled flame spread measurement — Alt: “ASTM E84 Steiner Tunnel test for spray foam flame spread index”
2. Cross-section of UL-listed 2-hour fire-rated steel stud wall with closed cell spray foam and dual layers of Type X gypsum — Alt: “UL fire-rated wall assembly with spray foam insulation and gypsum thermal barrier”
3. Spray foam with intumescent coating being applied via airless sprayer — Alt: “Intumescent fire barrier coating application on spray foam insulation”