Glossary / noncombustible
Noncombustible
A material that does not ignite or burn in standard tests such as ASTM E136. Concrete, steel, and gravel are typical examples. It is stricter than ignition-resistant.
Noncombustible is a test result, not a feeling about a material. A material is noncombustible when a small specimen does not ignite or burn in the ASTM E136 vertical-tube furnace at 750 °C; the codes treat that pass as noncombustible. Concrete, steel, gravel, brick, stucco and metal are the everyday examples. Where Oregon R327 is adopted, R327.2 defines noncombustible by ASTM E136 and lists a noncombustible wall covering as one path among ignition-resistant, heavy timber, log or a tested assembly. Colorado's 2025 CWRC (section 202) also counts a material as noncombustible if no part will ignite and burn, or if it is fire-rated gypsum board tested to ASTM C1396 with a one-hour rating from the outside.
Stricter than ignition-resistant. Ignition-resistant means a material passed a named ignition test, in Oregon an extended ASTM E84 or UL 723 run; it can still burn. Fiber cement is the family people mix up: some OSFM category 8140 siding listings name ASTM E136 and a noncombustible rating, others list a model without it. The rating belongs to the listed model.
Where the word does work. Zone 0: IBHS Wildfire Prepared permits noncombustible hardscape in the first five feet and removes combustible groundcover. Vents: the prescriptive path is noncombustible, corrosion-resistant metal mesh. Fences and gates within five feet of the house: IBHS replaces combustible material with noncombustible. Decks: Oregon R327 accepts noncombustible material for walking surfaces 30 inches to 12 feet above grade. A plant this site rates fire-resistant is never noncombustible; that guide explains the difference, and the siding hub holds the listed wall products.
Questions
What does non-combustible mean?
That a specimen did not ignite or burn under a named test, ASTM E136 in the codes on this site. It is a laboratory result for a material, not a promise about an assembly or a whole house.
Which metal is non-combustible?
Steel and the other structural metals the codes rely on for mesh, gates and roofing pass ASTM E136. A coated or composite product is judged as the listed product, not by the base metal alone.
What is the best non-combustible material?
The codes do not rank them. Concrete, masonry, stucco, steel and gravel each pass the same test; the choice is the element's job, siding, deck surface, hardscape or vent mesh, and the listing for a manufactured product.
Is masonry noncombustible?
Brick, concrete block and stone are the everyday examples the codes treat as noncombustible, and Colorado's CWRC names noncombustible hard surfaces for the first five feet. A masonry veneer over wood framing is a noncombustible covering on a combustible wall, which is exactly the Oregon R327 wall path; the rating stays with the material, not the whole wall.
What types of construction are considered noncombustible?
In the wildfire books on this site, noncombustible is a material path per element: wall covering (Oregon R327), deck walking surface (R327 and Colorado CWRC), vent mesh, and the first-five-feet hardscape and fencing (IBHS). Building-code construction types are an interior fire-resistance classification, a different question.
Related
- ignition resistant
- zone 0
- Fire-resistant plants are not noncombustible
- Fire-resistant is not fireproof
Where this term is used
- Artificial turf in Zone 0
- ASTM E119 versus a WUI wall test
- Bird blocks, boxed soffit, or unvented attic
- California AB 38 seller disclosure
- California FAIR Plan
- Char rate
- Chimney spark arrestors
- Colorado CWRC versus Oregon R327 versus California CWUIC