Subfloor for Type I and II construction
Direct answer: Type I and II are the non-combustible construction types, so the structural floor deck must be a non-combustible material (ASTM E-136) — which rules out plywood and OSB. JARA High Performance Subfloor is a fiber-cement structural panel that is non-combustible per ASTM E-136, ASTM E-84 Class A, and UL R15140 classified for 1-hour and 2-hour fire-rated floor/ceiling assemblies, with IBC 2021 Type I/II recognition and California Building Code Chapter 7A compliance for wildfire zones.
Why plywood and OSB do not qualify
IBC Chapter 6 sorts buildings into construction Types I through V, and the dividing line between Types I/II and the rest is combustibility: the building elements in Type I and Type II construction are required to be non-combustible. Non-combustible is not a marketing adjective in this context — it is a pass on ASTM E-136, in which specimens are held in a vertical tube furnace at 750 °C and judged on weight loss, temperature rise, and sustained flaming.
Wood-based panels do not pass that test. Fire-retardant treatment does not change the outcome either: treatment improves surface-burning performance measured under ASTM E-84, but a fire-retardant-treated wood panel is still a combustible material. This is the distinction that most often surfaces late in a project — a product sheet advertising a Class A flame spread is describing ASTM E-84 results, not ASTM E-136 non-combustibility, and only the latter satisfies the Type I/II material requirement.
What a Type I/II subfloor must satisfy
- Non-combustible material
- ASTM E-136 non-combustibility is the defining test for Type I/II elements.
- Surface burning
- ASTM E-84 Class A (flame spread 0, smoke developed 0).
- Fire-rated assembly
- UL R15140 classified assemblies (H502, H504, H511, U449, U487) for 1-hour and 2-hour floor/ceiling ratings.
- Code recognition
- IBC 2021 Type I/II references (§602, §711, §803, Table 601); IAPMO ER-360 evaluation report.
- Wildfire (WUI)
- California Building Code Chapter 7A + §420 for Wildland-Urban Interface zones.
Material property vs. assembly rating
Two separate requirements run in parallel, and a complete submittal has to answer both. The first is the material question — is the deck non-combustible? That is ASTM E-136, and it is a property of the panel itself. The second is the assembly question — does the floor/ceiling carry the hourly fire-resistance rating that Table 601 requires for this construction type and building element? That rating belongs to a tested assembly, not to any single product in it, and it is established by a listed design that fixes the deck, the framing, the fasteners, the cavity, and the ceiling membrane.
For this panel the applicable UL designs are H502, H504, and H511 for wood- and steel-joist floor/ceiling assemblies, plus U449 and U487, spanning 1-hour and 2-hour ratings under UL file R15140. Substituting a component — a different fastener schedule, a different ceiling board, a different joist spacing — voids the listing. Specify the design number, not just the product.
Where it is specified
Multifamily Type V over a concrete podium, hotels, steel-joist Type I/II commercial floors, and modular construction — assemblies where a combustible plywood deck is not permitted or where the floor/ceiling must carry a fire rating. JARA provides the UL assembly references, ASTM reports, and the IAPMO evaluation report needed for AHJ submittal.
In California, projects inside a Wildland-Urban Interface zone pick up a further layer: CBC Chapter 7A governs materials and construction methods for exterior wildfire exposure, which is why the Chapter 7A reference appears alongside the IBC citations in the compliance dossier.
Common questions
Can plywood or OSB be used as subfloor in Type I or II construction?
Not as the non-combustible structural deck. Plywood and OSB are combustible materials and do not pass ASTM E-136, so they cannot serve as a building element required to be non-combustible in Type I and Type II construction. The IBC does permit limited combustible components in otherwise non-combustible buildings — sleepers, nailing blocks, and finish flooring are addressed separately — but that is an allowance for specific components, not a path to a combustible structural deck.
Is "fire-rated" the same as "non-combustible"?
No, and conflating them is the most common specification error on this topic. Non-combustible is a property of the material, established by passing ASTM E-136. A fire-resistance rating is a property of an assembly — a specific tested build-up of deck, framing, and ceiling — expressed in hours and established by a tested design such as a UL H-series or U-series listing. A material can be non-combustible and still be in an unrated assembly; an assembly can carry an hourly rating while containing combustible components. Type I and II construction requires the non-combustible material property, and Table 601 separately drives the hourly rating.
What does an AHJ typically ask for on a non-combustible subfloor submittal?
Usually four things: the ASTM E-136 non-combustibility report for the panel, the ASTM E-84 surface-burning report, the specific UL assembly design number matching the rating and framing type on the drawings, and an evaluation report tying the product to the adopted code edition. JARA supplies these as a submittal package on request.
Does a podium deck over Type V construction need a non-combustible subfloor?
It depends on how the building is classified. A concrete podium with Type V wood-frame construction above is typically a horizontal building separation, and the podium slab itself is the non-combustible element. Where a project instead classifies the upper floors as Type I or II — common in hotels and mid-rise multifamily built on steel or light-gauge framing — the floor deck in those levels must be non-combustible. Confirm the construction type per level with the design team before selecting the deck material.
Sources & verification
Every code and certification claim on this page traces to the body that issues it. Verify against the source before specifying — JARA supplies the underlying reports for AHJ submittal on request.
- IBC 2021 Chapter 6 — Types of Construction — International Code Council
Defines construction Types I–V and establishes that Type I and Type II require non-combustible building elements — the reason a combustible plywood or OSB deck does not qualify.
- ASTM E136 — Behavior of Materials in a Vertical Tube Furnace at 750 °C — ASTM International (standard sold by the publisher)
The non-combustibility test method the IBC uses to qualify a material as non-combustible. Our "non-combustible" claim means the panel passes this test, not that it is merely fire-resistant.
- IBC 2021 Chapter 7 — Fire and Smoke Protection Features — International Code Council
Governs fire-resistance-rated floor/ceiling assemblies and how a tested assembly rating is established and documented.
- UL Product iQ — certification and assembly directory — UL Solutions (free account required)
Where UL file R15140 and the referenced fire-rated assembly designs (H502, H504, H511, U449, U487) can be looked up against UL’s own records rather than taken on our word.
- ASTM E84 — Surface Burning Characteristics of Building Materials — ASTM International (standard sold by the publisher)
The flame-spread and smoke-developed test behind the Class A rating cited on product pages.
- California Building Code Chapter 7A — Materials and Construction Methods for Exterior Wildfire Exposure — International Code Council / California Building Standards Commission
The Wildland-Urban Interface requirements referenced by the CBC Chapter 7A compliance claim.
- IAPMO Uniform Evaluation Service — IAPMO UES
The body that issues the ER-series evaluation reports, including ER-360, and the authoritative place to confirm a report’s current status and validity window.
Related guides
- Fiber-cement vs plywood subfloor — the material comparison behind the code requirement on this page.
- Non-combustible subfloor cost — delivered DDP pricing per thickness and how to estimate a project.