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Stucco in the WUI
Stucco can be a noncombustible covering when the material, in the form used, meets ASTM E136. Where Oregon R327 is adopted, that is one numbered wall path, not a skip of extent, weeps, or penetrations. Cracks and hose bibs are still holes. IBHS names stucco as an example at the six-inch base and, at Plus, as a whole-wall covering. It is not automatically the whole house.
You are looking at a hairline crack above the weep screed, or at a hose bib with daylight around the pipe. The field is cementitious. The hole is still a hole.
CMP-006 lives on ignition-resistant versus noncombustible. DET-016 is not published. Do not use a house-level hub graphic as a stucco section.
Why it matters
Embers enter at openings, not only at vinyl. A noncombustible face with an open annulus is the penetration problem. Full-height extent is still R327.3.3.1. See wall covering termination.
How the rules split
| Document | Stucco |
|---|---|
| R327.3.3 item 1 | If it is noncombustible per E136 in the form used |
| R327.3.3.1 | Still foundation to roof |
| IBHS Base | Example of the six-inch base |
| IBHS Plus | Example of a noncombustible whole covering |
| FEMA | Flash the bottom of all claddings, including noncombustible. Seal openings |
This page does not claim the weather-resistive barrier behind stucco is noncombustible. That document was not opened.
The paths
1. Oregon noncombustible covering. Confirm E136 for the mix as used. Run it full height. Seal penetrations.
2. Type X behind another face. Different path. See Type X.
3. IBHS. Six inches at Base, all walls at Plus. Do not write six inches onto R327.3.3.1. See wall base.
What people mix up
- “Stucco is fireproof, so the wall is done.”
- Six inches of stucco as R327.3.3.1.
- Ignoring cracks and bibs.
- Inventing a paper-behind listing.
How to check
- Name the R327.3.3 path.
- Walk the first course and the eave stop.
- Look at every pipe and crack.
- If scoring IBHS, measure six inches and the rest of the wall separately.
Limits
This page does not spec a mix design or a lath listing. FireApproved is not the AHJ.
Related records
Questions
Is stucco automatically R327?
Noncombustible material is ASTM E136 in the form used. If the stucco assembly meets that, it can be the R327.3.3 noncombustible path. The covering still has to run from the foundation to the roof. Confirm the mix and the lath with the official. Do not treat a crack as a listing.
Does the paper behind stucco need to be noncombustible?
This page did not open a paper-behind-stucco test. R327.3.3 is the covering or assembly you install. Type X behind cladding is a deemed-to-comply exception. Do not invent a WRB listing.
Is stucco the IBHS six-inch band?
IBHS Base lists stucco among examples of six inches of noncombustible material at the base. Plus wants the whole covering noncombustible. Those are designation sentences, not R327.3.3.1.