Valley Repair and Rebuild Standard

Purpose

A valley is the only part of a shingle roof where two planes hand their water to one channel, and it fails at the one place a repair is most tempting to shortcut: the middle. This procedure guarantees that a valley repair runs from sound material above the damage all the way down to the eave, so no lap in the finished work faces up-slope, and that the lining under the valley is replaced rather than covered.

The callback this prevents is the tidy-looking patch spliced into the middle of a run, which sheds water into the course below it for one season and then behind it forever.

Scope

Covers repair and partial rebuild of open metal, closed-cut and woven valleys in steep-slope asphalt shingle roofs, residential and small commercial: extent of opening, valley lining, fastener keep-back, and termination at the eave.

Does not cover full slope replacement, which the asphalt shingle replacement SOP owns, or a dead valley terminating into a wall or a low-slope area, which is a low-slope detail under the low-slope repair standard. Does not cover gutter and drip edge work at the valley outlet beyond confirming it is clear, which the gutter integration SOP owns. Course lifting and hand sealing belong to the shingle repair and blend-in standard.

Roles and responsibilities

Extent is the whole decision

Water in a valley is the runoff of two planes traveling in one line, so the volume at any point is the tributary area above it on both sides. That is why a valley fine for ten years fails in a month once anything interrupts it, and why extent is not a judgment call. Every lap in a finished valley has to face down-slope, and a splice ending part way up the run puts an upward-facing edge in the channel carrying the most water on the roof.

So the rule is: open from the first sound, dry lining above the highest damage, and continue down to the eave. Up-slope you stop at lining that is intact and dry, then add a lap so the new tucks under the old. Down-slope you do not stop at all - a repair ending 3 ft above the eave has moved the joint somewhere the customer cannot see it.

Two details govern the rebuild. Fasteners stay back from the centerline by the distance the shingle instructions state, commonly 6 in, because a fastener in the channel is a hole in the channel. And metals in a wet channel have to be compatible: copper against aluminum or bare steel sets up galvanic corrosion that eats the more active metal at the waterline. Pull the valley lining requirement from the roof covering chapter of the code edition your jurisdiction has adopted rather than from memory.

Procedure

1. Set access and fall protection, and treat the valley as the slide path. Access runs under the ladder setup standard and the fall protection setup SOP. Acceptance: anchorage set above the valley head, everyone connected, and the lifeline rigged so nobody has to cross the valley to reach their anchor. Wrong looks like a tech traversing a wet valley on the way to tie off. Stop rule: nobody enters the valley before anchorage. Hazard: a valley is the steepest travel line on the roof and valley metal under granule dust is the slickest surface on it, so this is where a slip becomes a fall - the duty triggers at 6 ft under 29 CFR 1926.501(b)(13), with arrest criteria at 1926.502(d).

2. Identify the valley type and read the whole run, top to bottom. Determine whether it is open metal, closed-cut or woven, then walk the full length including the head and the outlet. Acceptance: the type written down, plus a condition note at the head, at each visible fastener in the channel, and at the outlet into the gutter or off the drip edge. Wrong looks like a scope written from the leak location alone. Stop rule: a blocked outlet or a debris dam is cleared and re-inspected before any repair is scoped, because the dam may be the whole cause. Hazard: reaching into a packed valley outlet finds fasteners, glass and wildlife, so use a hook and a gloved hand, never a bare one.

3. Find the highest compromised point and set the opening extent. Probe the channel and the courses either side for soft deck, corroded metal, exposed fasteners and lifted cut edges. Acceptance: a marked highest damage point, a marked extent that runs from the next full course above it down to the eave, and that length recorded in linear feet before anything is opened. Wrong looks like a marked rectangle in the middle of the run. Stop rule: if the highest damage cannot be bounded because the courses will not lift, the visit converts to a diagnostic and the customer is told the extent is unknown rather than being given a number. Hazard, commercial: quoting from the stain rather than from the probe is how a valley job doubles on site with nobody prepared for the conversation.

4. Open the valley and keep opening until the lining is sound and dry. Lift and remove courses on both planes per the shingle repair and blend-in standard, take out the old metal or the cut shingles, and expose the lining. Acceptance: at the top of the opening, lining that is intact, bonded and dry to the touch across the full width, confirmed on both planes. Wrong looks like stopping at the planned mark because that is what was quoted. Stop rule: wet, wrinkled or delaminated lining means keep opening up-slope until it is sound, then stop and call the estimator with the new opened length before more material is ordered. Hazard: removed courses and old metal stack up on a slope with a channel down the middle, so material goes to the ground as it comes off rather than being staged in the valley.

5. Replace the deck if needed, then the lining, with every lap facing down-slope. Probe the sheathing across the opened width, replace anything soft back to framing centerlines, then run new self-adhered valley lining centerd on the line, tucked under the existing lining above by the manufacturer's stated lap. Acceptance: lining continuous and centerd to full width, up-slope end under the existing lining, down-slope end carried over the drip edge at the eave, no fish mouths or trapped wrinkles. Wrong looks like new lining laid on top of the old at the up-slope joint. Stop rule: a wrinkle that will not roll out is cut, lapped down-slope and re-rolled, not pressed and ignored. Hazard: self-adhered membrane on a slope is slick before it is rolled and adheres to boots, so it is set from the eave upward with the release film pulled in stages rather than all at once.

6. Rebuild the valley to its type, with the fastener keep-back and compatible metals. Reinstall open valley metal in lengths lapped down-slope by the manufacturer's stated minimum, or re-lay closed-cut courses with the cut line and the offset the instructions call for. Acceptance: no fastener within the stated keep-back distance from the centerline on either plane, laps all facing down-slope, and every metal component and fastener compatible with the others in the channel. Wrong looks like a nail through valley metal an inch off the centerline. Stop rule: a fastener found inside the keep-back is pulled, the hole is patched with self-adhered membrane, and the piece is refastened outside the line before work continues. Hazard: cutting valley metal produces sharp offcuts and burrs that sit in the channel where hands go, so deburr, pouch offcuts, and keep cut-resistant gloves on for the whole rebuild.

7. Re-lay the courses, hand seal above the opening, and prove the run with a flow test. Re-lay both planes to the original exposure, hand seal every course you unsealed above the top of the opening per the shingle repair and blend-in standard, and then run water into the head of the valley for at least 10 minutes with an observer inside. Acceptance: tabs above the opening tug-tested and holding, water leaving the outlet freely, and a dry interior after the full dwell. Wrong looks like a crew leaving on the strength of how the valley looks from the ridge. Stop rule: any interior water during the flow test reopens the run on this visit. Hazard: this step returns the roof's highest-volume channel to service, and the flow test at full length is the only field evidence the path you rebuilt actually carries and discharges; run it top down so the whole rebuilt length is loaded, not just the bottom.

The record this produces

A valley entry carrying: valley type and outlet condition; the highest compromised point as found; planned and final opened length in linear feet with the reason for any change; deck replaced with its extent; the lining product, width and lap onto the existing lining above; the fastener keep-back and which instruction set it; metals and fasteners installed; courses re-laid per plane; shingles hand-sealed above the opening; and the flow test dwell and result.

The estimator reads the planned-versus-final length, because that gap is what makes the next valley quote honest. The next tech reads the keep-back and the lining product so a future repair laps into the same system.

Worked pass: 18 ft closed-cut valley, 8:12 and 6:12 planes, leak 7 ft up

Complaint is a hallway ceiling stain already attributed to the valley by water test. Step 1: anchor set above the valley head, both techs connected without crossing the channel. Step 2: closed-cut valley, outlet into a gutter packed with granules and needles, cleared and re-inspected. Step 3: probing puts the highest damage 7 ft up from the eave, so the planned opening runs from the next full course above that down to the eave, recorded as 7 ft 6 in.

Step 4 fails. With the courses off, the lining is wrinkled and wet well past the planned mark, and the crew does not reach intact, dry, bonded lining on both planes until 12 ft 6 in from the eave. The stop rule fires: work pauses, the estimator is called, and the customer is told the opened length went from 7 ft 6 in to 12 ft 6 in before more material is ordered.

The field is a laminated shingle at 5-5/8 in exposure. The planned 7 ft 6 in is 90 in, which at 5.625 in per course is exactly 16 courses per plane. The final 12 ft 6 in is 150 in, which is 26.67, so 27 courses per plane, 54 in total, or 11 more per plane than planned. New lining is the 12 ft 6 in opened plus a 6 in lap under the sound lining above, so 13 ft, centerd and full width from the drip edge up.

Step 5: two sheets probe soft at the 9 ft mark and are replaced back to framing centerlines. Step 6: closed-cut rebuilt with the cut on the steeper plane per the shingle instructions, no fastener inside the 6 in keep-back they state, all laps down-slope. Step 7: eight shingles above the opening hand-sealed at four spots each, so 32 dabs, all eight holding; water into the valley head for 10 minutes discharges freely and the ceiling stays dry.

The 5 ft gap between the planned 7 ft 6 in and the final 12 ft 6 in is the finding. The leak showed at 7 ft because that is where the deck was soft enough to let water through, not where it entered: measured from that leak point, the lining had been failing for 12 ft 6 in minus 7 ft, or 5 ft 6 in above it, and a repair stopping at the stain would have been reopened inside a year.

References

• 29 CFR 1926.501(b)(13) and 1926.502(d), the fall protection duty and arrest criteria governing roof access for this work
• IRC Chapter 9, in the edition your jurisdiction has adopted, for valley lining material and width requirements by valley type
• The shingle manufacturer's installation instructions for the product installed, which set the fastener keep-back from the valley centerline, the cut-line offset for closed-cut valleys, and the metal lap minimum
• See related: the shingle repair and blend-in standard, the leak diagnosis by water testing SOP, the gutter integration SOP for the valley outlet, and the flashing and penetration detail inspection SOP