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Exterior FRT wood and weathering
Fire-retardant-treated wood is a factory treatment, not a paint. Where Oregon R327 is adopted, exterior FRT wood is one numbered walking-surface path (R327.3.5 item 3). Ignition-resistant material is a 30-minute ASTM E84 or UL 723 run. FEMA P-737 warns that treatments and coatings have service-life uncertainty, and it does not recommend wood roof coverings. A field-applied coating is not this product.
You are reading a stamp on a deck board. Exterior use, retention, and species are on that stamp. They are not a spray can.
MECH-002’s Steiner tunnel lives on ASTM E84. This page is weathering and the FRT vs coating split. Do not use a house-level hub graphic as a treatment stamp.
Why it matters
Treatments can fade. FEMA says so in public. Oregon still names exterior FRT as a path. Those facts travel together. A coating on siding is the miss the seminar named. See spray-FRT special inspection.
How the words split
| Word | What it is | What it is not |
|---|---|---|
| Exterior FRT wood | R327.3.5 item 3 walking surface | A wall covering by itself |
| Ignition-resistant | R327.2 30-minute tunnel | A coating |
| Wood roof | Not permitted where R327.3 applies | FRT shakes as a Class A skip |
| Spray-on retardant | Seminar special inspection | Factory FRT |
The paths
1. Walking surface. If you use item 3, spec exterior FRT wood. Put the treatment standard and the stamp on the drawings. The 200 square foot 2-inch lumber exception is a different sentence. See that exception.
2. Walls. Ignition-resistant or Type X or noncombustible. Not a brushed coating. See ignition-resistant versus noncombustible.
3. Roofs. Wood shingles and shakes are out where R327.3 applies. FEMA does not recommend wood roofs regardless of rating. See covering versus assembly.
4. Do not invent a year count. If the maker publishes a re-treat interval, that is their document. This page did not open AWPA.
What people mix up
- Spray-on as factory FRT.
- FRT shakes as an R327 roof.
- A 10-minute E84 as ignition-resistant.
- FEMA’s weathering warning as a BCD ban of item 3.
How to check
- Read the stamp. Exterior, or not.
- Name which R327 sentence you are using.
- If someone proposes a coating, that is a different page.
Limits
This page does not open AWPA or a retreatment table. FireApproved is not the AHJ. FEMA is a builder guide.
Related records
Questions
Does exterior FRT stay treated forever?
This page does not invent a service life. FEMA P-737 cites uncertainty around ignition-resistant treatments and applied coatings, and does not recommend wood roof coverings regardless of test rating. Read the treatment standard and the manufacturer’s exterior-use instructions for that product.
Is factory FRT the same as spray-on retardant?
No. R327.3.5 names exterior fire-retardant-treated wood as a walking-surface path. Spray-applied retardant is what the 25 June 2026 seminar flagged for special inspection. Coatings are not an R327.3.3 wall path.
Is FRT ignition-resistant?
Ignition-resistant in R327.2 is an extended E84 or UL 723 run with listed acceptance. Exterior FRT wood is a separate numbered walking-surface item. Do not swap the words. See ignition-resistant versus noncombustible.