Roof valleys do the quiet, relentless work on a shingle roof. Every raindrop that lands on two intersecting slopes eventually funnels into that V, then rides it down to the gutters. Snow load stacks there. Debris collects there. If a roof leaks, odds are good the valley is involved. Replacing a valley is not simply a matter of laying new shingles. It’s a sequence of decisions about layout, water management, and material compatibility. Get those right, and the valley will outlast most of the field shingles. Get them wrong, and you get callbacks, rot, and a homeowner who never looks at you the same way again.
I have rebuilt valleys that failed in five years and others still tight after two decades. The difference rarely comes down to brand of shingles. It’s craftsmanship, sequence, and the small details you only learn after finding your own mistakes under a pry bar in February.
How valleys actually move water
Water is lazy and opportunistic. On a gable-to-gable valley, the flow accelerates as it collects, then twists slightly where pitches or roof planes are uneven. On a closed-cut valley, water will ride the shingle laps and try to sneak under angled cuts if they end on a high spot or a nail head. In an open metal valley, water rides the metal and pushes under the shingle edges during wind-driven rain if the edge hem or sealant strategy is wrong. Debris changes the equation entirely. Leaves that sit on a woven valley wick water uphill, and pine needles dam open valleys until the next storm sends a surge.
When planning roof shingle installation or roof shingle replacement, start by reading the roof. Note pitch on both planes, direction of prevailing wind, the nearest downspout, and any tree canopy. If one slope is significantly steeper, you control the flow with the cut lines and underlayment laps. If the valley ends to a short gutter run, you may consider crickets or diverters below, but the valley itself still needs to carry most of the runoff without help.
Choosing a valley style: closed, open, or woven
There are three common valley styles on asphalt shingle roofing, and each has a place.
Closed-cut valley. The shingles from one roof plane run through the valley, then the opposing plane’s shingles are laid over and cut along a chalk line, exposing a clean, angled seam. It looks tidy and matches most architectural shingle patterns. Properly detailed, it handles moderate water volumes well. It is my default on 6/12 to 9/12 pitches where debris is not a chronic problem.
Open metal valley. A strip of valley metal is centered in the valley, and shingles from both sides stop short, leaving a visible channel. It moves water quickly and sheds debris better than closed valleys. It shines on low to moderate pitches that see heavy water, on any roof under big trees, and where snow and ice are common. Flashing metal introduces different failure points, so you must know how to hem, fasten, and isolate dissimilar metals.
Woven valley. Shingles from each side interlace across the valley. It can perform well on three-tab shingles, especially on midrange pitches. It is bulky with thicker laminated architectural shingles, which can create bumps that telegraph through the finish and catch debris. I avoid woven valleys on laminated shingles and on cold-weather installs where stiff shingles won’t conform.
The style you choose affects the entire shingle roof. Closed-cut valleys need precise cut lines and nail placement discipline. Open valleys require a commitment to quality flashing. Woven valleys demand flexible shingles and patience. A shingle roofing contractor who treats valleys as an afterthought is asking for trouble.
Tear-off and diagnosis, not demolition
Before any roof shingle repair or replacement in the valley, slow down. Tear off gently and learn from what you find. Leaks often leave maps.
I start wide. Strip shingles at least three feet back on both planes. Pull nails carefully so you don’t crater the decking. Look for darkened underlayment, unsealed nail penetrations, and rot at the center line. If the valley is cut over a joint in the sheathing, check for deflection underfoot. In older homes, multiple layers of roofing hide soft spots around valley troughs. If you can push a screwdriver into the deck, replace that section. Fit replacement plywood or board sheathing so seams never land directly in the valley center. I like to shift seams at least six inches off the centerline.
If you find corrosion stains, note the metal type that was there. Copper stains green, galvanized steel dulls and rusts reddish-brown, aluminum chalks. If dissimilar metal contact caused galvanic corrosion at fasteners, plan to isolate materials with compatible underlayment and sealants.
When you re-sheathe, keep your fasteners flush, not overdriven. High nails under a valley live a hard, short life. In winter, they’ll help ice lift shingles. In summer, they’ll wear a hole in the underlayment.
Underlayment is not optional protection, it is the first defense
Valleys need layered defenses. The underlayment system matters more here than on the field. On any roof shingle installation, I treat valleys as a high-risk area and use self-adhered ice and water barrier. Not all membranes are equal. A robust SBS-modified bitumen membrane with high tack bonds to clean decking and seals around nails. Avoid bargain peel-and-stick that turns brittle after a few seasons.
I run membrane a minimum of 18 inches past the centerline on each side. On low-slope valleys, heavier snow zones, or shaded valleys that hold ice, I push that to 24 inches each side. If you’re using a two-course approach, lay the first course from one side and cross the center. Then lap the second course from the opposite side so the top lap faces the downslope water flow. At the bottom, extend the membrane past the fascia and into the gutter line. That way, if the metal or shingles fail later, the membrane still escorts water out.
Before the membrane, sweep and vacuum the deck. Dust kills adhesion. If the temperature is below manufacturer thresholds, a primer improves bond. In hot climates, roll the membrane with pressure instead of just pressing it by hand.
Once the valley membrane is down, install your field underlayment on the rest of the deck. The laps should always shingle over, never back-lap into the valley. Where https://gunneryglv247.theglensecret.com/how-to-extend-the-life-of-your-shingle-roofing field underlayment meets the valley membrane, I prefer a 3 to 4 inch overlap with the valley membrane on top. That way wind-driven rain traveling under field shingles meets a curb, not a ramp.
Drip edge, starter, and the often-ignored bottom detail
The bottom of the valley is where many leaks start. Poor sequencing leaves three layers fighting for dominance: drip edge, valley metal (if used), and underlayment. The best sequence largely depends on whether you are installing an open metal valley or a closed-cut valley without exposed metal.
For open valleys, install eave drip edge first, then run the valley membrane over it. Your valley metal rests on top of the membrane and empties into the gutter. At the eave cut, hem the metal’s lower edge into a small kick so water does not climb back under by capillarity. For closed-cut valleys without exposed metal, the membrane still laps onto the drip edge, and the starter shingles should run through the valley far enough to anchor the first course cleanly. Starter shingles need to align so factory seal strips are inboard of the cut line and won’t glue the waste you will remove later.
Always prove the path. Pour a gallon of water from two feet up and watch it leave the roof. You’ll see immediately if you created a dead pocket or a lip at the gutter.
Open metal valley installation details that hold up
If you choose an open valley, the metal becomes the workhorse. Common gauges for residential valleys are 26 to 24 gauge for galvanized steel and aluminum, and 16 to 20 ounce for copper. Heavier material resists oil canning and impact dents. Width matters more than many realize. I prefer 24 inches minimum, often 26 to 28 inches on large roof areas. After hemming both edges, you’re left with an exposed channel of 6 to 8 inches, which is generous without looking industrial.
Hem both sides. A 1/2 inch to 3/4 inch closed hem stiffens the edge and creates a small standoff that helps prevent capillary backup under shingles. If you forgo hems, you must create a raised rib or use adhesive backer strips to limit capillary action, but hems are cleaner and stronger.
Center the metal with a true chalk line. Fasten high, never in the water path. I place clips or pancake-head screws just outside where the shingle edge will cover them, every 12 to 18 inches. Avoid nailing through the middle of the valley, no matter what. Where sections overlap down the slope, I like a 6 inch overlap with a thin bead of high-grade, compatible sealant near the top of the lap. Less is more with sealant. Squeeze-out that sits in the flow path will trap grit, grow a scab, and divert water sideways.
Under the metal, the ice and water membrane provides the primary waterproofing. Do not count on caulk as your safety net. When setting the metal, leave thermal movement room at the ridge and eave. On long valleys, slot the upper fastener holes on the metal to accommodate expansion without oil canning.
Once the metal is in, cut and place your valley underlay shingles. Some roofers use a “California cut” starter strip along the valley edge to support the field shingle ends. It works, but keep nails out of the valley zone. Manufacturers often specify a no-nail zone 6 inches away from the center. Respect it. When laying the field shingles, stop short to reveal an even channel. The reveal width should stay consistent within a quarter inch. Crooked reveals draw the eye and hint at sloppy support underneath.
Closed-cut valley technique that avoids capillary wicking
Closed-cut valleys look simple, but the cut line is a water management device. I start by shingling the valley with the “under” side first. Typically, I run shingles from the lesser-visible slope through the valley, onto the opposing plane by at least 12 inches. Snap a line on the under course to keep courses straight. Do not nail within 6 inches of the centerline.
Next, bring the shingles from the “over” side into the valley. Before cutting, lay them across, hand-pressing to seat them without distorting the under course. Now snap a cut line. On a 6/12 to 8/12, a 2 inch offset from the centerline is common. On steeper slopes or where wind-driven rain comes from a particular side, increase that offset to 3 inches on the windward side. The idea is to move the cut seam onto the side less favored by water. Small adjustments here make big improvements in performance.
The dog-ear cut at the top of each shingle is a small but critical move. Trim the top corner of the over-shingle back about 1 inch at a 45 degree angle so water cannot catch the corner and run sideways. This tiny relief keeps the flow in the valley.
When you cut, use a sharp hook blade and cut on a sacrificial shingle rather than cutting directly over the installed under course, especially in hot weather when you risk gouging the surface. Lift the waste gently so you don’t tear the adhesive bond of the under course. After cutting, place a discrete dollop of roofing cement (not a smear) on the under-shingle near the cut, about 1 inch back. You are not gluing the valley shut. You are just tacking the edge to resist uplift. Excess cement turns into a dam for grit.
Nail placement is the other deal-breaker. Keep nails at least 6 inches from the centerline, more on low slope or open-grain plywood. I have traced many leaks to a single nail head 4 inches off the valley line that someone thought was “close enough.”
Woven valley: when to use it and how to avoid bulges
If you are installing three-tab shingles and the climate stays warm enough during installation for shingles to flex, a woven valley is a cost-effective and durable option. Lay one side across the valley, then the opposing side across that, alternating courses so the valley is woven. Keep the weave flat and snug. The weight of laminated architectural shingles works against you in a weave, creating a ridge that slows water and traps debris. If a client insists on woven with laminated shingles, explain the trade-offs and the visual outcome. Most will accept a closed-cut once they see a mockup.
With woven valleys, discipline matters. Never press nails into the valley area. Keep the weave centered with occasional chalk checks. In cold weather, shingles crack when forced to bend, and a cracked tab hidden in a weave will leak in the first freeze-thaw cycle.
Ice, snow, and cold-weather considerations
In snow country, valleys carry meltwater under crusted snow and ice dams. The primary defense remains the ice and water membrane beneath. Beyond that, build in small design choices that help.
On open valleys, consider slightly wider exposure so meltwater has space even when slush fills part of the channel. Avoid smearing mastic along the shingle edges, which traps ice and breaks the bond when it expands. If the home has a history of ice dams, suggest additional intake and exhaust ventilation and air sealing in the attic rather than trying to solve it with the roof surface alone. A well-executed valley cannot overcome a 20 degree attic with warm, moist interior air.
Cold-weather installation introduces stiffness. Warm your bundles in the sun and keep your hook blades fresh. Seal strips won’t bond at low temperatures. Use hand-sealing sparingly, placing small dabs where the manufacturer recommends, and only on clean, dry surfaces. Excess cement becomes a magnet for grit that later undermines the seal.
Valleys on mixed pitches and asymmetrical roofs
Many replacement projects involve two slopes with different pitches. Picture an 8/12 main roof meeting a 4/12 addition. The steeper plane throws water faster and with more energy. In a closed-cut valley, cut the over-shingles from the steeper slope so the seam lives on the lower-flow side, generally the shallower plane. Increase the cut offset to shift the seam further away from center, giving water a smoother path.
On open valleys where pitches differ, the metal still centers, but your shingle stops will be unequal. Keep the exposed reveal consistent by varying how far each side steps back under the shingle edges. Keep your no-nail zone intact, even if that means adjusting course layout slightly near the valley to avoid crowding.
Valleys that kink or jog, common in dormer tie-ins, require shorter metal sections and careful shingling to avoid backwater. Do not try to force a single piece of metal around a dogleg. Overlap sections so the upper piece laps over the lower with the lap line out of the main water path, and use a concealed cleat or a soldered joint for copper. Step your shingles to follow the new centerline, and re-snap chalk lines after the jog. I sometimes pre-test with a hose on complex shapes before committing to final nailing.
Fasteners, adhesives, and compatibility
Use corrosion-resistant fasteners that match your environment and materials. In coastal zones, stainless or hot-dipped galvanized nails outperform electro-galvanized. If you are installing a copper open valley, avoid aluminum nails or steel that will start a galvanic reaction. For aluminum valley, stay away from copper runoff above, such as from copper ridge or gutters, or isolate with coatings.
Adhesives matter. Roofing cement is not a fix-all. A thin, well-placed dab under a shingle edge is acceptable; wide smears become dams. For copper laps, rely on solder, not sealant. For steel or aluminum laps, a compatible butyl-based sealant holds up better than generic asphalt mastic. Read the shingle manufacturer’s valley details. Warranties often require a specific technique, and following their diagram helps both performance and paperwork.
Debris, trees, and maintenance expectations
A roof under a maple or pine canopy needs a valley that forgives neglect. An open valley sheds leaves and needles better than a closed-cut. If a homeowner will not commit to seasonal cleaning, lean toward open metal. Set clear expectations. Even the best valley will choke if six months of needles compost in it. Discuss gutter guards and whether they help or hurt in that house’s specific layout. Some guards push water into the valley during heavy rain; others starve the gutters and cause overflows right where the valley empties.
I tell clients to look up at the valley after the first major storm. If they see lines of grit building where the shingle edge meets the valley, that is a sign to rinse the channel. A simple garden hose from a ladder is enough. Avoid pressure washers that drive water upward.
Sequencing the work on a live roof
Replacing one valley on an otherwise functional shingle roof is delicate. You can’t expose more than you can dry-in before weather shifts. Stage materials and cut metal beforehand. Strip, repair decking, and install valley membrane the same day. If weather threatens, stop after the membrane, lap temporary field underlayment over it, and tarp high. Do not leave a valley metal installed without shingles to hold down the edges, unless you secure with temporary battens outside the water path. On multi-valley roofs, never open adjacent valleys at once. Keep at least one intact so stormwater has a dependable route if a surprise squall arrives.
Common failure patterns and how to avoid them
Several valley mistakes show up again and again on roof shingle repair calls.
- Nails within 6 inches of the centerline. Under driving pressure and a little capillary backing, those nails become leak points. Train crews with a bright temporary chalk warning line while they lay courses. Back-lapped underlayment. If field underlayment tucks under the valley membrane uphill, wind-driven rain will find the seam. Always shingle your layers down-roof. Overuse of mastic. Cement smeared along edges catches grit and ice, forming speed bumps that throw water sideways. Cut lines on the wrong side. A closed-cut seam on the windward side pulls water under. Spend five minutes with a compass and local wind data or look at staining patterns on the old valley. Metal valleys without hems. Raw edges invite capillary infiltration. A simple hem reduces callbacks by a surprising margin.
Specifics by shingle type
Three-tab shingles are forgiving in valleys and remain the best candidate for woven installations. They lie flat and allow tight bends without bulging. Keep course alignment perfect; any jog telegraphs prominently where tabs interlace.
Laminated architectural shingles are heavier and stiffer. They perform best in closed-cut or open valleys. Pay attention to the laminated shadow lines. When you cut, follow the manufacturer’s layout guidance to avoid exposing an unattractive layer edge at the valley seam. Hand seal selectively along the cut in cold weather.
High-impact shingles behave like laminated shingles but can be even stiffer when cold. Warm them for tight, clean cuts. Some products specify wider no-nail zones near valleys. Read the wrapper and keep it on-site for reference.
Safety and setup that keep everyone intact
Valleys are slippery and concentrate foot traffic. Use roof jacks and planks to stage above and below the valley. Never step directly in a bare metal valley. If you must work in the channel, cover it with a padded plank to distribute weight and protect the metal. Harness tie-off points should be set high and centered, not off to the side where a fall might swing a worker into the valley.
Cutting with hook blades near the valley always risks slicing the underlayment. Place a scrap shingle under your cut to protect what you just installed. Sweep as you go. Granules underfoot are like ball bearings on a slope.
Pricing and scope, explained to the homeowner
Valley replacement costs vary by region, pitch, access, and whether you choose open metal or closed-cut. As a rough range on a single-story, walkable roof, a straightforward closed-cut valley replacement can run a few hundred dollars in labor and materials, while an open copper valley on a steep, two-story roof might be several times that. If rot repair is needed, add time and material for decking replacement. A good shingle roofing contractor will set a clear scope: how far shingles will be removed, what underlayment will be used, the valley style, metal type if applicable, and how they will address discovered damage. Clarity prevents friction when hidden rot appears under old layers.
A short field sequence that works
- Strip shingles and underlayment at least 3 feet each side, inspect, and repair decking offset from centerline. Clean and prime if needed. Install self-adhered membrane 18 to 24 inches each side, laps shingled downhill, and extend into the gutter line. For open valleys, install eave drip, then center and fasten hemmed valley metal with high, concealed fasteners. Overlap sections with 6 inches and minimal sealant. Install field underlayment with laps over the valley membrane. Lay starters correctly through the valley. Shingle the under side through the valley with no nails within 6 inches of center. Then bring the over side in, snap a cut line offset from center, dog-ear the tops, and place discrete tacks of cement as needed. For open valleys, hold shingle edges back to maintain a consistent reveal. Test with water at the top, watch the flow, and make small adjustments before final nailing the last courses.
What separates a durable valley from a pretty one
A clean chalk line and tidy cut make a valley look good on day one. Durability shows up in storms five years later. Hemmed metal edges. Nails kept out of the danger zone. Underlayment that makes sense when you peel back shingles a decade later. A slight shift of the cut line to favor the dominant wind. These are quiet decisions that define the craft.
Whether you are tackling roof shingle repair on a single valley or planning a full roof shingle replacement, give valleys the extra hour they deserve. The best shingle roofing jobs fail at their weakest point. Done right, the valley becomes the strongest part of the roof, the place where you stand in the rain with a satisfied homeowner and watch the water run exactly where it should.
Express Roofing Supply
Address: 1790 SW 30th Ave, Hallandale Beach, FL 33009
Phone: (954) 477-7703
Website: https://www.expressroofsupply.com/
FAQ About Roof Repair
How much should it cost to repair a roof? Minor repairs (sealant, a few shingles, small flashing fixes) typically run $150–$600, moderate repairs (leaks, larger flashing/vent issues) are often $400–$1,500, and extensive repairs (structural or widespread damage) can be $1,500–$5,000+; actual pricing varies by material, roof pitch, access, and local labor rates.
How much does it roughly cost to fix a roof? As a rough rule of thumb, plan around $3–$12 per square foot for common repairs, with asphalt generally at the lower end and tile/metal at the higher end; expect trip minimums and emergency fees to increase the total.
What is the most common roof repair? Replacing damaged or missing shingles/tiles and fixing flashing around chimneys, skylights, and vents are the most common repairs, since these areas are frequent sources of leaks.
Can you repair a roof without replacing it? Yes—if the damage is localized and the underlying decking and structure are sound, targeted repairs (patching, flashing replacement, shingle swaps) can restore performance without a full replacement.
Can you repair just a section of a roof? Yes—partial repairs or “sectional” reroofs are common for isolated damage; ensure materials match (age, color, profile) and that transitions are properly flashed to avoid future leaks.
Can a handyman do roof repairs? A handyman can handle small, simple fixes, but for leak diagnosis, flashing work, structural issues, or warranty-covered roofs, it’s safer to hire a licensed roofing contractor for proper materials, safety, and documentation.
Does homeowners insurance cover roof repair? Usually only for sudden, accidental damage (e.g., wind, hail, falling tree limbs) and not for wear-and-tear or neglect; coverage specifics, deductibles, and documentation requirements vary by policy—check your insurer before starting work.
What is the best time of year for roof repair? Dry, mild weather is ideal—often late spring through early fall; in warmer climates, schedule repairs for the dry season and avoid periods with heavy rain, high winds, or freezing temperatures for best adhesion and safety.