Roof Valleys in Minnesota: Open vs Closed vs Woven Explained
13min Read
Posted 4.13.2026
If you have ever looked up at a roof during a heavy rain, you have seen exactly what a roof valley does: two cascades of water from adjoining roof planes collide, concentrate, and rush down a single channel. Now imagine that water freezing, thawing, and accumulating as snowpack for three or four straight months — and you begin to appreciate why roof valleys are a perennial source of leaks in Minnesota homes. A valley carries more water per square foot than almost any other part of your roof, and when ice dams form, the valleys are where they form first and deepest.
This guide explains the three valley construction styles, which one is right for Minnesota, what the IRC requires, and why valley design is one of the single most important decisions you’ll make during a roof replacement — second only to attic ventilation and ice-and-water shield placement.
What Is a Roof Valley, Exactly?
A valley is the internal angle formed where two roof slopes meet and drain together. On a typical American gable-and-hip suburban roof, you will see valleys wherever a dormer meets the main roof, wherever an L-shaped or T-shaped house intersects, and at every hip-and-valley pitch transition. A simple rectangular gable roof has zero valleys; a complex modern home may have eight or more. Every additional valley increases leak risk and installation cost.
Valleys carry a disproportionate volume of water. As a rule of thumb, a valley drains roughly twice the square footage of roof that its direct geometry suggests, because the two planes above it both funnel into it. That concentration of water — plus, in Minnesota, the weight and hydraulic pressure of ice and snowmelt backing up behind ice dams — is what makes valleys so leak-prone.
The Three Valley Construction Styles
1. Open Metal Valley
In an open valley, the shingles are cut back on both sides to expose a strip of metal flashing (typically 18″–24″ wide) down the center of the valley. The exposed metal handles the water flow directly. This is the historically traditional valley style and remains the preferred option for Minnesota in snow and ice conditions, because the metal surface sheds water and ice far more efficiently than a shingle-covered valley, and it physically prevents the interlaced shingle joints that can lift under ice-dam pressure.
- Pros: best water shedding, easiest debris clearance, least vulnerable to ice dams, cleanest long-term appearance as the metal develops patina
- Cons: highest material cost, requires skilled installation (metal hemming, clip fastening), some homeowners find the exposed metal less aesthetically integrated
- Best for: Minnesota homes, especially north of the metro; any home with large valleys or complex roof geometry
2. Closed-Cut Valley
In a closed-cut valley, the shingles from one roof plane run fully across the valley, while the shingles from the other plane are cut back 2″ from the valley centerline. No metal is visible; the valley is entirely covered by shingles (sitting on top of a membrane underlayment). This is currently the most common residential valley style nationally because it is faster to install and looks “cleaner” from the ground.
- Pros: lower labor cost, uniform shingle aesthetic, fewer exposed metal edges
- Cons: shingle granules can lodge in the valley and reduce flow, cut-line can lift under ice pressure, harder to clean debris
- Best for: milder climates, simpler valley geometry, homeowners prioritizing aesthetic uniformity
3. Woven Valley
In a woven valley, shingles from both roof planes alternate across the valley, interweaving each course. It was common in the 1970s–1990s with 3-tab shingles but is largely obsolete today and explicitly prohibited by many modern shingle manufacturers with thick architectural laminates. GAF, Owens Corning, and CertainTeed all specify closed-cut or open valleys for their current architectural product lines.
- Pros: historically traditional, no exposed metal, no cut line
- Cons: warranty-voiding on most modern shingles; architectural shingles are too thick to weave cleanly; creates many small entry points for water
- Best for: essentially no modern application — avoid
Open vs Closed vs Woven: Side-by-Side
| Criterion | Open Metal | Closed-Cut | Woven |
|---|---|---|---|
| Water shedding | Excellent | Good | Fair |
| Ice-dam resistance | Excellent | Good | Poor |
| Debris clearance | Easiest | Harder | Very hard |
| 2026 MN installed cost | $12–$18 per lf | $7–$11 per lf | Not quoted |
| Modern warranty-eligible? | Yes | Yes | Typically no |
| Aesthetic integration | Visible metal stripe | Monolithic shingle | Monolithic shingle |
| Typical lifespan | Matches shingle + 0 | Shingle minus 3–5 yr | Shingle minus 5–10 yr |
Minnesota Code Requirements for Roof Valleys
Minnesota adopts the International Residential Code with local amendments. The relevant valley specs are in IRC R905.2.8.2:
- Valley linings must be installed before shingles.
- For open valleys: one ply of smooth roll roofing (min 36″ wide) or equivalent self-adhered membrane, with metal flashing at least 24″ wide, 0.019″ (26 gauge) minimum thickness for aluminum, copper, or galvanized steel.
- For closed valleys: one ply of self-adhering polymer-modified bitumen sheet (ice-and-water shield) minimum 36″ wide, running the full length of the valley.
- All valleys in Minnesota should have ice-and-water shield as the membrane layer, not just felt — this is industry standard even where not strictly code-required, because valleys are the #1 leak point in ice-dam territory.
If your Minnesota roofing estimate does not explicitly specify ice-and-water shield in the valleys (not just at the eaves), ask the contractor to add it. This is also essential coverage if you’re in an area prone to ice dams — see our detailed guides on ice dam prevention and roof underlayment.
Metal Valley Material Options
| Metal | Gauge / Thickness | 2026 Installed $/lf | Lifespan | Notes |
|---|---|---|---|---|
| Aluminum | 0.019″–0.027″ | $11–$16 | 40–60 yr | Most common; lightweight, corrosion-resistant |
| Galvanized steel | 26–24 ga | $10–$14 | 25–40 yr | Good but eventually rusts at edges |
| Galvalume steel | 26–24 ga | $12–$17 | 40–60 yr | Al-Zn coated; better than plain galvanized |
| Copper | 16 oz | $28–$45 | 75+ yr | Premium; beautiful patina; limited Minnesota use |
| Lead-coated copper | 16 oz | $35–$55 | 100+ yr | Historic restoration only |
Aluminum is the practical default for almost every Minnesota home; the material cost difference between aluminum and galvanized steel is small, and the corrosion resistance is meaningfully better. Copper is gorgeous but typically reserved for higher-end architectural homes or churches and museums.
W-Profile vs V-Profile Valley Metal
Open-valley metal flashing comes in two primary profiles:
- W-profile: has a raised center bead running down the middle of the flashing. This acts as a splash guard, preventing water traveling down one slope from shooting across the valley centerline and back-flooding under shingles on the opposite plane. W-profile is the Minnesota standard.
- V-profile: flat or V-shaped center with no center bead. Lower cost, but no splash protection. Avoid in Minnesota where snowmelt volumes are high.
If an estimate specifies “open valley with metal flashing” but does not say W-profile, ask the contractor to confirm. The extra cost for W-profile over V-profile is minimal and the performance difference in ice country is substantial.
Valley Waterproofing Stack-Up: What Goes Where
A properly built Minnesota open-metal valley has five layers, from deck up:
- Deck: 7/16″ OSB or 1/2″ plywood, solid nailed every 6″ on edges, 12″ in field.
- Ice-and-water shield: 36″ wide minimum, centered on valley, lapped at least 6″ onto any joints.
- Metal flashing: 18″–24″ wide W-profile aluminum, hemmed edges, clip-fastened (not nailed through the flashing itself).
- Synthetic underlayment: overlapping onto the outer edges of the metal flashing.
- Shingles: cut back from valley centerline with a clean 3″–4″ offset per side, sealed with roofing cement only at the cut edges.
A closed-cut valley has only three layers: deck, ice-and-water shield (full valley length, 36″ wide), and shingles running across then cut back on one side. The metal flashing layer is absent — which is why closed-cut valleys are cheaper, but also why ice-and-water shield in the valley is absolutely non-negotiable.
When Do Roof Valleys Leak?
Most valley leaks in Minnesota happen during ice-dam season (mid-January through mid-March), when meltwater backs up under shingles from ridging ice at the eave. The valley, because it concentrates snow and ice, is usually the first place to back-flood. A well-built open metal valley with 36″ ice-and-water shield and a W-profile will resist back-flooding up to several inches of standing water.
The second most common cause is debris accumulation. Valleys collect leaves, pine needles, and seed pods; when the valley clogs, water backs up, freezes, and expands. Annual gutter-and-valley cleaning (late fall, after leaf drop) is one of the cheapest and most valuable maintenance tasks you can do. For a full Minnesota-specific maintenance schedule, see our seasonal roof maintenance calendar and annual inspection checklist.
Repairing vs Replacing a Leaking Valley
| Condition | Recommendation | 2026 MN Cost |
|---|---|---|
| Small leak, minor staining, shingles < 10 yr old | Spot repair: re-seal cut edges, verify membrane | $450–$950 |
| Extensive staining, shingles 10–15 yr old | Valley tear-off + rebuild with new metal + I&W | $1,400–$3,200 per valley |
| Rotted decking under valley | Partial re-deck + new valley | $2,200–$4,800 |
| Shingles > 18 yr old, multiple leaks | Full roof replacement with open metal valleys | $14,500–$22,000 |
If your shingles are more than 15 years old and you are seeing valley leaks, a single-valley repair is usually a bandage — the rest of the roof is not far behind. In that scenario it is almost always better to replace the whole roof. See our guide on roof repair vs replacement to evaluate your specific situation.
Choosing the Right Valley Style for Your Minnesota Home
Our recommendation for nearly every Minnesota home: open W-profile aluminum valleys with 36″ ice-and-water shield underlayment. The extra $400–$800 on an average 3-valley home (roughly $150–$250 per valley beyond closed-cut) pays back many times over in reduced leak risk and longer valley lifespan. The only cases where closed-cut makes sense in Minnesota are (a) very short valleys (under 6 linear feet), (b) very shallow pitches where metal runoff noise is concern, or (c) tight aesthetic matching on a historic home.
Never accept a woven valley on a new installation in Minnesota. If an old woven valley is leaking, rebuild it as open metal — do not re-weave.
What Owl Roofing Customers Actually Say
Real, verified Google reviews from real customers Owl Roofing maintains a 5.0 Google rating with 30+ five-star reviews.
Noah is the real deal. After our insurance denied our roof claim and the first roofer walked away, Noah showed up the next day and said he thought he could get us a new roof. He delivered. He got us a roof covered by insurance after it had already been declined. We came up with a nickname for him: “The Roof Whisperer.”
— Tyler Moberg, verified Google review
I am an Independent Insurance Agency owner and have worked with Noah on several roof projects. The homeowners have been extremely satisfied with the quality of work and craftsmanship Noah and his crews have provided. From filing the claim to replacing the roof and cleaning up the job site, Noah and his crew are the best!
— Fred Zappa, Independent Insurance Agency Owner
We used Owl Roofing for a repair on our roof in Brooklyn Park, and I was blown away by how good they were. Every member of the team communicated well about the process. Their price transparency was super helpful. They got the work done very fast, and the team was professional and very kind.
— Matt Brown, Brooklyn Park (verified Google review)
Noah and his team are outstanding! His clear communication, professionalism, and workmanship are top-notch. I recommend Owl Roofing to all my clients, friends, and family.
— Christine Westlund, verified Google review
It didn’t feel like dealing with a big company — it felt like working with people who actually care about the homes and community in the North Oaks and Shoreview area. Great people, great communication, and really solid work.
— Cody Warren, verified Google review
Frequently Asked Questions
What’s the best valley style for a Minnesota roof?
Open metal valleys with W-profile aluminum flashing and full-length ice-and-water shield underlayment. Best water shedding, best ice-dam resistance, easiest debris clearance.
How much does a roof valley cost to install in 2026?
Open metal valleys run $12–$18 per linear foot installed in the Twin Cities; closed-cut runs $7–$11 per linear foot. A typical home has 30–50 linear feet of valleys total.
Do I need ice-and-water shield under my valleys?
Yes. IRC R905.2.8.2 requires valley lining, and in Minnesota’s climate, self-adhered ice-and-water shield is the only responsible choice. Felt underlayment alone is inadequate in the valleys.
Are woven valleys allowed under modern shingle warranties?
Typically no. GAF, Owens Corning, and CertainTeed specify open or closed-cut valleys for their current architectural shingle lines. Woven valleys void or reduce the warranty on most modern shingles.
Why do valleys leak more than other parts of the roof?
Valleys concentrate water and debris from two roof planes. In Minnesota, they also accumulate snowpack and develop ice dams. Higher water volume + ice-dam pressure = more leak opportunities than any other single roof feature.
Can I install metal valleys on an existing closed-cut roof?
Converting a closed-cut valley to open metal requires removing the shingles in the valley area, installing new ice-and-water and metal, and reinstalling shingles. It’s typically done during a full roof replacement — a standalone conversion is rarely cost-effective.
How often should I clean my roof valleys?
Annually, in late fall after leaf drop — usually combined with gutter cleaning. If you have overhanging trees, twice a year (spring and fall). Clean valleys are a major contributor to shingle longevity.
