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Vinyl siding in the WUI
Vinyl can melt. FEMA P-737 says not to use vinyl, wood, or polypropylene cladding in wildfire zones, and notes that vinyl does not burn but melts. Where Oregon R327 is adopted, the wall is a covering or assembly menu. Noncombustible is ASTM E136. Vinyl is not that test. Type X behind cladding is a different path than the vinyl itself.
You are looking at melted cladding on a post-fire photo, or at a vinyl spec on a Bend lot that adopted R327. Those are different documents.
CMP-006’s wall menu lives on ignition-resistant versus noncombustible. This page is the vinyl mistake. Do not use a house-level hub graphic as a melt sequence.
Why it matters
Melted vinyl can open the wall to embers and heat, or drip. A “does not burn” marketing line is not E136. A coating on vinyl is not an R327.3.3 path. See the coatings finding.
How the rules split
| Document | Vinyl |
|---|---|
| FEMA P-737 | Do not use as cladding. Melts rather than burns |
| R327.3.3 | Not a named path. Covering still needs a numbered option or Type X / 1-hour behind |
| IBHS Plus | Wall covering itself noncombustible. Wood and IR treatments not permitted |
| IBHS Base | 6-inch noncombustible at the base. See wall base |
The paths
1. Oregon. Pick a numbered R327.3.3 path. If you keep vinyl as the face, the path is behind it (Type X or 1-hour), not the vinyl. Confirm with the official. Extent still runs foundation to roof.
2. FEMA. Do not spec vinyl, polypropylene, or untreated wood cladding in that guide.
3. IBHS Plus. Noncombustible covering. Vinyl fails that sentence.
What people mix up
- “Vinyl doesn’t burn, so it is noncombustible.”
- Treating Type X behind vinyl as an E136 pass for the vinyl.
- Coatings as a wall path.
- IBHS Base’s six-inch band as permission for vinyl above it.
How to check
- Name R327 vs IBHS vs FEMA on the sheet.
- If R327, name the 3.3 path, not the brand of vinyl.
- If IBHS Plus, the covering itself has to be noncombustible.
Limits
This page does not spec a fiber-cement SKU. FireApproved is not the AHJ. FEMA is a builder guide. IBHS is a designation.
Related records
Questions
Is vinyl banned by Oregon R327?
R327.3.3 lists noncombustible, ignition-resistant, heavy timber, log, or an ASTM E2707 assembly, plus Type X or a one-hour wall as deemed-to-comply. Vinyl is not ASTM E136 noncombustible. If it is the covering, it still needs one of those paths behind or instead of it. FEMA’s builder guide says not to use vinyl cladding in wildfire zones.
If Type X is behind the vinyl, is the vinyl the path?
No. Type X behind the covering is the deemed-to-comply wall path. The vinyl is still combustible cladding. IBHS Plus wants the wall covering itself noncombustible and does not permit wood siding even with ignition-resistant treatments.
Does melting vinyl protect the wall?
FEMA notes some materials such as vinyl do not burn but melt. Melting is not an E136 pass and not an R327 covering path by itself.