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Deck railings in the WUI
FEMA P-737 (2008) Fact Sheet 13 says embers accumulate at railing edges. It recommends metal, cables, tempered glass, or 3-inch nominal fire-retardant-treated wood. Oregon R327 .3.5 is the walking surface, not the guard. Dimensional lumber railings are what that sheet tells you to replace.
You are at the top of the stair, holding a 2x2 baluster in one hand and a metal picket in the other. The walking surface may already pass R327.3.5, or sit under the 200 square foot 2-inch lumber exception. The rail is a different object. Embers lodge along it and against the wall.
No g3-passed exhibit matches this object. DET-004 is the deck band, not the guard. The scene is the rail. Do not use a house-level hub graphic as a guard detail.
Why it matters
People treat the deck as one material. R327 splits walking surface from underside. FEMA then names railings as a third ignition edge. A legal 2x deck with a basket of 2x2s still collects embers at the perimeter and against the siding. That is how a “compliant” deck lights the wall. See deck ledger and the wall.
How the documents split
| Object | What decides it | What it is not |
|---|---|---|
| Walking surface | R327.3.5, including the 200 ft² 2-inch lumber exception | The guard |
| Underside / underfloor | R327.3.4, including Type X behind covering | The rail |
| Railing (FEMA P-737 FS13) | Metal, cables, tempered glass, or 3-inch nominal FRT wood | A walking-surface listing |
| Columns (same sheet) | Minimum 6×6 timber, CMU, or steel | This page |
The paths
1. Name the rail on the drawing. FEMA’s new-work list is short. Metal. Cables. Tempered glass. Or 3-inch nominal fire-retardant-treated wood. Dimensional lumber rails are the existing-deck replacement item on the same sheet.
2. Do not hide it under R327.3.5. Where R327 is adopted, that subsection is the walking surface in the 30-inch to 12-foot band. Guards still have to meet the stair and guard chapter of the adopted residential code. This page does not reprint those heights and openings.
3. Do not hide it under the 2-inch exception. Two-by lumber is a small walking surface. It is not infill.
4. Watch the wall. FEMA says embers accumulate at railing edges and settle against exterior walls. A metal rail that stops at combustible siding still needs the ledger and the wall covering. Tempered-glass infill is not a window listing.
5. Composite. Fact Sheet 13 does not recommend plastic or composite decking in high fire-severity zones. It does not list composite as a railing material. A board listing is not a guard. Confirm with the building official.
What people mix up
- Calling the rail “the deck” under R327.3.5.
- Stretching the 200 square foot 2-inch exception onto balusters.
- Speccing a window as a guard because both say tempered.
- Treating FEMA 3-inch FRT as ignition-resistant lumber under R327.2 without reading the FRT standard.
- Pasting FEMA’s 1/4-inch soffit weep (underside drainage on the same sheet) onto Oregon vent mesh. Different object.
How to check
- On the drawing, find a railing note. If it only says “match decking,” stop.
- Read R327.3.5. Confirm you are not in the walking-surface subsection.
- Open FEMA P-737 (2008) Fact Sheet 13. Match metal, cable, tempered glass, or 3-inch FRT.
- Look at the wall behind the rail. Ledger, flashing, six-inch band.
- Ask the official which guard chapter applies. This page is not that chapter.
Limits
This page does not size a guard. It does not set infill openings. It does not decide a composite rail. FireApproved is not FEMA and not the AHJ. The 2025 P-737 draft on disk is pre-decisional and is not a source here.
Related records
Questions
Does R327 specify a railing material?
No. R327.3.5 is deck, porch, and balcony walking surfaces in the 30-inch to 12-foot band. R327.3.4 is the underside of projections. Neither subsection names guards or handrails. FEMA P-737 Fact Sheet 13 is guidance. Confirm with the building official and the stair/guard chapter of the adopted residential code.
Does the 200 square foot 2-inch lumber exception cover the rail?
No. That exception is the walking surface of a small deck. It is not the guard. See the 200 square foot 2-inch lumber deck exception.
Is tempered-glass railing the same as a tempered window?
FEMA lists tempered glass as a railing material. Dual-pane versus tempered windows is a different hole in a different wall. Do not spec a window listing as a guard.
Are composite rails a pass because the decking listing is Class B?
FEMA’s 2008 sheet does not recommend plastic or composite decking in high fire-severity zones, and it does not list composite as a railing material. It names metal, cables, tempered glass, or 3-inch nominal fire-retardant-treated wood. A walking-surface listing is not a rail.