ULC Fire-Rated Design Numbers Explained for Ontario Structural Steel & Decks (2026 CAN/ULC-S101 F900, D900 & Z600 Spec Guide)

ULC Fire-Rated Design Numbers Explained for Ontario Structural Steel & Decks (2026 CAN/ULC-S101 F900, D900 & Z600 Spec Guide): 2026 Ontario Overview & Code Essentials

When an architect, structural engineer, or municipal plans examiner in Toronto, Mississauga, Brampton, Vaughan, Hamilton, or Ottawa reviews a Part 3 commercial building permit, specifying "1-hour or 2-hour fireproofing on structural steel" on the general notes sheet is never sufficient for occupancy sign-off. Under Ontario Building Code Division B Section 3.1.7 (Fire-Resistance Ratings) and CAN/ULC-S101 (Standard Methods of Fire Endurance Tests of Building Construction and Materials), every protected steel column, wide-flange girder, open-web steel joist (OWSJ), and fluted composite concrete floor deck must reference an exact Underwriters Laboratories of Canada (ULC) Fire-Rated Design Number—such as ULC Design No. F906, ULC Design No. D902, ULC Design No. Z608, or ULC Design No. O905—and be installed by a qualified cementitious fireproofing and intumescent fire coating contractor.

At Sprayfoam Solutions Toronto Inc., we serve Ontario general contractors, steel fabricators, and industrial developers as a Single-Source Certified Spray Foam & Fire Coating Contractor with Caliber Certified (CAN/ULC-S705.2 Licensed) Installers and specialized Division 07 fireproofing crews. Whether your project requires pumping standard or medium-density cementitious Spray-Applied Fire-Resistive Materials (SFRM) across a multi-storey steel deck, spraying architectural thin-film intumescent coatings onto exposed W-shapes and HSS columns, or coordinating a Turnkey 2 lb Closed-Cell Spray Foam + 18-Mil DC315 Thermal Barrier Package with IFTI DC315 fire coating at the exterior envelope transition, decoding ULC design numbers before tender close prevents five-figure change orders. Get a $250 Credit on Your Estimate — Check Your Price in 60 Seconds (/price-chat) • No Site Visit Required, or send your structural steel schedule and architectural fire matrix to our General Contractor & B2B Estimating Desk.

2026 ULC Fire-Resistance Assembly & Cost Table (45-Min to 4-Hr Structural Steel & Deck Ratings in Ontario)

In 2026, installed commercial pricing for CAN/ULC-S101 structural steel fireproofing in Ontario ranges from $2.25 to $5.85 per square foot for cementitious fireproofing (SFRM) (MasterFormat 07 81 16) and $5.50 to $10.50+ per square foot for thin-film intumescent fire coatings (MasterFormat 07 81 23), while 18-mil IFTI DC315 thermal barrier coating over spray foam (CAN/ULC-S124) averages $1.75 to $3.25 per sq ft. The exact thickness and square-foot cost depend on the specified ULC Design Number, the required hourly fire-resistance rating (45 min, 1 hr, 1.5 hr, 2 hr, 3 hr, or 4 hr), and each steel member’s Weight-to-Heated-Perimeter (W/D or M/D) ratio:

Decoding ULC Fire-Resistance Design Number Prefixes (F, D, Z, O, W, I & P Series Explained)

In the UL Product iQ / ULC Online Directories and the National Building Code / Ontario Building Code Division B Appendix D, every fire-resistance design number begins with an alphabetical prefix that identifies the exact structural assembly type and test geometry, followed by a three-digit series code indicating the protection category (900-series and 600-series typically denote spray-applied cementitious or intumescent coatings directly applied to steel without a suspended lath-and-plaster ceiling):

Restrained vs. Unrestrained Beam & Assembly Ratings in CAN/ULC-S101 (Why It Changes Your Coating Thickness by 30%–50%)

One of the costliest mistakes general contractors and estimators make when pricing a ULC D902 or ULC F906 specification is confusing Restrained Assembly / Restrained Beam ratings with Unrestrained Assembly / Unrestrained Beam ratings. During a fire, structural steel loses approximately 50% of its yield strength at 538°C (1,000°F) (CAN/ULC-S101 critical temperature criteria). When a steel beam is welded or shear-connected to a heavy cast-in-place concrete floor slab and surrounded by rigid structural bays that resist thermal expansion, rotational thermal stresses are absorbed by the surrounding frame (Restrained). Conversely, simple-span roof joists, cantilevers, or light framing that can expand freely must support the dead load purely through the steel’s own flexural capacity (Unrestrained):

• 1. Restrained Beam Thickness Savings (Typically 3/8" to 5/8" SFRM for 1–2 Hr): In a standard composite concrete-over-metal-deck floor (ULC F906 or ULC D902), if the engineer of record confirms the steel framing is thermally Restrained, a W250x49 (W10x33) wide-flange beam (W/D = 0.84) typically requires only 9.5 mm (3/8") to 13 mm (1/2") of standard cementitious fireproofing for a 1-hour to 2-hour rating.
• 2. Unrestrained Beam Thickness Escalation (Often 3/4" to 1-3/8"+ SFRM): If that exact same beam is classified as Unrestrained—which is common in open-web steel joist (OWSJ) roof assemblies, mechanical penthouses, or non-composite retrofits—the required CAN/ULC-S101 limiting steel temperature drops significantly, increasing the required SFRM thickness by 30% to 55% (or adding 30 to 65 mils DFT of intumescent paint).
• 3. How W/D (Weight-to-Heated-Perimeter) & M/D Ratios Drive Material Takeoff: Heavy stocky columns (such as W360x196 with a high W/D ratio of 2.15) act as a massive thermal heat sink and require far thinner fireproofing than slender light sections (W200x36, W/D = 0.69) or thin-wall HSS hollow tubes (C/D ratio). Our commercial estimating team calculates the exact W/D ratio for every steel mark on your structural framing plan so you never over-buy chemical or fail a third-party pin-depth audit.
• 4. Open-Web Steel Joists (OWSJ) Minimum Chord & Web Sizing Rules: Many ULC roof and floor designs (ULC F906, ULC P902) base their standard SFRM or intumescent thickness on a minimum structural joist size (e.g., 10K1 or minimum web rod diameter). Undersized light joists require increased thickness adjustments per the ULC design footnotes.

Matching Approved SFRM & Intumescent Systems (Monokote, Cafco, Pyrocrete, Nullifire & Firetex) to ULC Listings

Under Ontario Building Code Division B Part 3, a ULC design number is not a generic permission slip to apply any brand of plaster or fire paint at an arbitrary depth. Every ULC design listing explicitly names the tested manufacturer product code and required minimum density. As a certified Division 07 fireproofing contractor, Sprayfoam Solutions Toronto Inc. installs and certifies Isolatek Cafco® 300, GCP Monokote® MK-6® / Z-106, Carboline Pyrocrete® / Nullifire® SC902, Sherwin-Williams Firetex® & other ULC-listed structural fireproofing systems:

When to Specify Standard 15 lb Gypsum SFRM vs. 22–40 lb Portland Cement SFRM vs. Thin-Film Intumescent Coating

Selecting the right material class within a ULC design family (F900, D900, or Z600) protects both your construction budget and long-term facility durability. While 15 lb/ft³ gypsum-based SFRM (Monokote MK-6 / Cafco 300) is the lowest-cost solution ($2.25–$4.10/sq ft) for concealed floor plenums above drop ceilings, Ontario building officials and project specifications mandate 22 lb/ft³ medium-density (Monokote Z-106 / Cafco 400) or 40 lb/ft³ high-density Portland cement SFRM (Monokote Z-146 / Pyrocrete 241) in unconditioned underground parkades, loading docks, elevator shafts, and mechanical rooms exposed to humidity, freeze-thaw cycles, or air velocities above 4.0 m/s. Where structural steel remains architecturally exposed to view (AESS lobbies, retail showrooms, offices, or gym mezzanines), intumescent fire coating provides a smooth, paint-like finish at 30 to 145 mils DFT without bulky fibrous texture.

Crucial Code Distinction: CAN/ULC-S101 Structural Steel Fireproofing vs. CAN/ULC-S124 (IFTI DC315) Spray Foam Thermal Barrier

On commercial warehouses, underground parkade soffits, and mixed-use buildings across the GTA, general contractors frequently need both structural steel fire-resistance (CAN/ULC-S101) and spray polyurethane foam thermal barrier protection (CAN/ULC-S124) under the same roof. Evaluated by the Canadian Construction Materials Centre (CCMC #14036-R), IFTI DC315 thermal barrier coating (18 mils WFT / 12 mils DFT) satisfies OBC Section 3.1.4.2 as a 15-minute thermal barrier over 2 lb closed-cell spray foam (see our Turnkey Warehouse Spray Foam + DC315 Guide and Commercial Warehouse Insulation Cost Guide). However, DC315 cannot be substituted for a 1-hour or 2-hour ULC Z600/F900 structural steel rating—and conversely, pumping wet cementitious SFRM directly over closed-cell spray foam violates ULC substrate adhesion rules unless engineered mechanical lath is installed. Because Sprayfoam Solutions Toronto Inc. operates both Caliber Certified (CAN/ULC-S705.2 Licensed) Installers and certified structural fireproofing crews, we sequence the ULC-S101 steel fireproofing before spraying the CAN/ULC-S705.1 foam and 18-mil DC315 envelope.

6 Critical GC Submittal, Sequencing & Third-Party QA Rules for ULC Fire-Rated Steel in Ontario

Passing a third-party geotechnical/materials inspection (WSP, EXP, Englobe, Pinchin, or Terraprobe) and municipal building official walkthrough on a commercial building envelope in Ontario requires strict adherence to ULC listing conditions. Here are the 6 non-negotiable field and submittal rules our fireproofing division follows on every project:

• 1. Fireproof Primary Structural Steel Before Spraying Polyurethane Foam or Hanging MEP Ducts: ULC column and beam designs (ULC Z608, ULC F906, ULC D902) require the fireproofing material to bond directly to clean, primed or bare structural steel. Never allow an insulation contractor to bury a fire-rated steel column in spray foam first, and always schedule SFRM or intumescent spraying before wide sheet-metal HVAC ducts, cable trays, and sprinkler mains block nozzle access to the upper beam flanges.
• 2. Verify Shop-Primer Compatibility & Galvanized Deck Bond (ULC Design Footnotes): Standard alkyd or zinc-rich shop primers and cellular/fluted galvanized roof decks can cause cementitious SFRM delamination or intumescent blistering if not matched to the manufacturer’s tested primer table. Where required by the ULC design number (e.g., ULC D902 or ULC P902), we apply approved bond-seal adhesives (Isolatek EBS / Monokote Type S) or compatible epoxy tie-coats before spraying.
• 3. Install Mechanical Hangers, Clips & Roof Deck Fasteners Before SFRM Application: Under OBC Division B Section 3.1.7, cutting or knocking off cured cementitious fireproofing to weld trapeze hangers, conduit clamps, or drywall tracks voids the CAN/ULC-S101 assembly rating. All structural attachments must be installed first, or budgeted for a certified pre-occupancy SFRM Patching & Re-Spray Pass prior to ceiling close-in.
• 4. Respect Cure Roof Loading & Concrete Pour Sequencing on Composite Decks: On fluted steel floor decks (ULC D902, ULC F906), never spray cementitious fireproofing onto the underside of a floor deck before the upper concrete slab is poured and cured, or before rooftop HVAC units are craned onto a roof deck. Mechanical deflection during concrete placement will crack the monolithic SFRM bond.
• 5. Enforce Canadian CCOHS, Ontario OHSA & Negative-Pressure Dust/Overspray Containment: We strictly follow Canadian Centre for Occupational Health and Safety (CCOHS) and Ontario Ministry of Labour (OHSA) commercial construction regulations. Once cured, our fireproofing and spray foam assemblies are chemically stable, fully cured, and odourless—and during application, our crews poly-mask glazing, curtain walls, bridge cranes, and ESFR sprinkler heads.
• 6. Deliver Complete ASTM E605, ASTM E736 & SSPC-PA 2 Inspection Logs: Every project handover includes our GC Submittal & Municipal Inspector Binder: ULC Design Number cut sheets, W/D thickness schedules, ASTM E605 pin-thickness and dry-density core logs (≥15 pcf or ≥22 pcf), ASTM E736 cohesion/adhesion pull-test records, and SSPC-PA 2 calibrated Elcometer magnetic Dry Film Thickness (DFT) reports for intumescent steel.

Cementitious SFRM vs. Thin-Film Intumescent vs. Type X Drywall Enclosures on Structural Steel (2026 Comparison)

When value-engineering a commercial tender or warehouse retrofit (see our Spray Foam for Metal Buildings Guide and DC315 vs. Drywall Comparison), architects and general contractors often weigh three ways to achieve a CAN/ULC-S101 structural steel rating. Here is how Cementitious SFRM, Thin-Film Intumescent Mastic, and Multi-Layer 5/8" Type X Gypsum Drywall Boxing compare in 2026:

Same-Week Commercial Fireproofing & Mobile Rig Dispatch Across Toronto, the GTA & Ontario

Every commercial structural steel fireproofing, intumescent coating, and turnkey spray foam project is executed by Sprayfoam Solutions Toronto Inc. as your Single-Source Certified Spray Foam & Fire Coating Contractor with Caliber Certified (CAN/ULC-S705.2 Licensed) Installers and $0 surrounding GTA travel fee across Toronto, Mississauga, Brampton, Vaughan, Markham, Oakville, Burlington, Hamilton, Pickering, Ajax, Whitby, Oshawa, Milton, and Barrie:

OUR 4-STEP ULC STRUCTURAL FIREPROOFING PROCESS

How We Take Your ULC Design Spec From Blueprint Takeoff to Occupancy Sign-Off

1

60-Second Quote & W/D Schedule Takeoff

Step 1 • Fixed B2B Tender Pricing

Get an instant ballpark at /price-chat or send structural steel plans for an exact W/D thickness takeoff matched to your ULC Design Numbers.

2

Primer Check, Deck Bond & Poly Masking

Day 1 • Substrate Verification

We verify steel surface cleanliness, shop primer compatibility, mechanical clips, and mask MEP equipment, glazing, and sprinkler heads.

3

ULC-S101 SFRM, Intumescent & SPF Application

Days 1–4 • Calibrated Application

High-production application of Monokote/Cafco SFRM, 3,000 PSI airless intumescent mastic, and turnkey 2 lb SPF + 18-mil DC315 transitions.

4

ASTM E605/E736 & Elcometer QA Binder Handover

Day 5 • Engineer & Inspector Sign-Off

Pin-depth, core density, bond pull-tests, calibrated Elcometer DFT logs, site cleanup, and complete ULC compliance binder delivery.