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Valley metal and cap sheet under R327.3
Where Oregon R327 is adopted and valley flashing is installed, the metal is not less than 0.019 inch (No. 26 gage) galvanized corrosion-resistant sheet. It sits over not less than one layer of 72-pound mineral-surfaced nonperforated cap sheet complying with ASTM D3909, not less than 36 inches wide, running the full length of the valley (amendment PDF). That stack is not a Class A stamp. It is not the same sentence as closing profile gaps under tile.
You are looking down a valley. The metal is the visible flashing. The 36-inch cap sheet is under it, for the whole run. A skinny valley coil with no cap sheet is not this detail.
The valley drawing (DET-008) is not published yet. Read the two sentences in R327.3. Do not use a roof-system hub graphic as the lead on this detail.
Why it matters
Valleys collect debris and embers. Thin or short flashing leaves a path onto combustible deck. R327 names the metal, the cap sheet, the width, and the length. If you spec “valley flashing per manufacturer,” plan review has nothing to match against those four numbers.
How the two roof sentences split
R327.3 does two different jobs after the covering list.
| Sentence | What it is for | What it is not |
|---|---|---|
| Profile gaps between covering and deck | Close the space, fireblock it, or install 72-pound ASTM D3909 cap sheet over combustible decking | A valley |
| Valley flashing, where installed | 0.019 inch (No. 26 gage) galvanized corrosion-resistant metal over 72-pound D3909 cap sheet, ≥36 inches wide, full length of the valley | A Class A assembly, a tile-gap fix, a shake permit |
Wood shingles and shakes are not permitted on structures in the section’s scope. See the wood-shake finding.
The paths
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Oregon R327, valley present. Install the named metal over the named cap sheet. Width not less than 36 inches. Full length. Corrosion-resistant galvanized. Not thinner than 0.019 inch.
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Oregon R327, profile gaps (tile, similar). Close, fireblock, or cap-sheet the deck. Do not treat that cap sheet as valley flashing.
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Class of the field of the roof. Still a tested assembly under ASTM E108 or UL 790, or the Chapter 9 covering R327 names as equivalent to Class B. See covering versus assembly and how to read a Class A roof listing.
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Colorado. CWRC 403.2.2 keeps the 0.019 inch metal and the 36-inch ASTM D3909 run. It does not name Oregon’s 72-pound cap sheet. Confirm the local ordinance.
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California. CWUIC is a different book. Class A field of roof is 504.2. Do not paste Oregon’s valley numbers onto that sheet without reading it.
What people mix up
- Using the tile-gap cap-sheet option as the valley detail, with no 26-gage metal.
- A 24-inch valley roll-out. The amendment says not less than 36 inches.
- Stopping the cap sheet short of the eave or ridge. Full length of the valley.
- Calling the valley stack a Class A listing.
- Treating “galvanized” as any shiny coil. The amendment names galvanized sheet corrosion-resistant metal at that thickness.
How to check
- Confirm R327 is the adopted code.
- If the roof has valleys, the drawing shows 26-gage (0.019 inch) galvanized metal over 72-pound D3909, 36 inches wide, full length.
- If the covering has profile gaps, a separate note closes, fireblocks, or cap-sheets those gaps.
- Do not hide either sentence behind “per manufacturer.”
- Confirm wood shake is not on the sheet.
Limits
This page does not spec laps, nails, or ice-and-water besides what R327 named. It does not host ASTM D3909. DET-008 is not published. FireApproved is not the AHJ.
Related records
Questions
Is valley flashing required on every R327 roof?
R327.3 says where valley flashing is installed, use the named metal over the named cap sheet. If the roof has no valley flashing, that sentence does not invent a valley. Confirm the roof type with the official.
Can I use the same 72-pound cap sheet as the tile-gap fix and skip the metal?
No. Profile gaps between covering and deck are a different sentence. They may be closed, fireblocked, or covered with 72-pound ASTM D3909 cap sheet over combustible decking. A valley that has flashing still needs the metal over a 36-inch-wide cap sheet for the full length of the valley.
Is 26 gage aluminum OK?
The amendment names galvanized sheet corrosion-resistant metal, not less than 0.019 inch (No. 26 gage). Do not swap in a thinner coil or an unnamed alloy from a brochure. Confirm with the official.
Does this make the roof Class A?
No. Class A, B, and C attach to a tested covering-on-deck. Oregon’s floor is a Class B-rated assembly equivalent. The valley stack is a flashing detail, not an ASTM E108 class.