Roof Valley Leaking: Causes, Identification, Emergency Fixes & Permanent Repair Solutions
Why roof valleys are vulnerable
Your roof valley is basically a target for leaks. After chimneys, valleys cause more roof leaks than any other part of your roof. About 30% of all leaks start right there.
Think of a valley as the V-shaped channel where two sections of your roof come together. All the water from both slopes rushes down into this one spot. That means your valley handles two to three times more water than the flat parts of your roof.
Three types of valley construction
Open valleys show the metal flashing underneath. The shingles on each side get cut back to expose that metal channel. You can see it from the ground.
Closed woven valleys hide the metal. Roofers weave the shingles from both slopes together over the valley. Looks cleaner but causes more problems down the road.
Closed cut valleys also hide the flashing. One side's shingles go right over the valley, then get cut along the center line. Same aesthetic as woven, same issues.
Six reasons valleys fail
Water volume hits valleys hard. When you funnel water from two roof sections into one narrow channel, any tiny weakness becomes a big problem fast. A small gap that would never leak on flat roof surface will pour water into your attic when its in the valley.
Debris piles up naturally in valleys. Leaves blow across your roof and get stuck where the slopes meet. Twigs and granules wash down and create dams. When debris blocks water flow, it pools up and seeps under your shingles.
Ice dams form in Ontario valleys every winter. Snow melts on your warm roof, runs down to the cold valley, and freezes solid. More meltwater backs up behind that ice and gets forced sideways under your shingles. We see this on almost every second roof inspection after a cold snap.
Installation mistakes happen often in valleys. Cutting and fitting shingles around a valley takes skill. Rush the job or skip steps, and you leave gaps that leak within months.
Valleys age faster than your main roof. Constant water flow wears down the materials. Debris scrapes against the surface. Your valley shingles might fail three to five years before the rest of your roof even shows its age.
Flashing corrodes over time. Metal valley flashing can rust through or develop pinholes. Seams between sections separate. And closed valleys without metal flashing offer zero backup protection when the shingles fail.
Identifying valley leaks
Valley leaks leave clues. Some are obvious, others hide for months before you notice the damage.
What you'll see inside your house
Water stains on your ceiling often follow a line. Trace that line back to your roof layout and it usually points straight to a valley. The stains might show up on multiple floors if your valley runs down through two stories.
Heavy rain makes valley leaks worse. A small leak might stay hidden during light drizzle, then pour buckets when a storm hits. That's because valleys handle so much more water volume than normal roof sections.
Long-term leaks show themselves through brown or yellow stains that keep spreading. Your paint peels. Wallpaper bubbles and falls off. The drywall gets soft when you push on it. Sometimes it sags.
Mold grows fast in wet areas. Look for black or green patches near the stains. You'll probably smell it before you see it - that musty odor tells you water's been getting in for a while.
Check your attic during rain
Head up to your attic right after it starts raining. Bring a flashlight and look at the area under your valley.
Active leaks show water running down the valley boards. Older leaks leave dark stains on the wood. Your insulation gets compressed and dark where water soaked through. Mold grows on the framing boards. Wood rot makes the boards soft and crumbly when you touch them.
Rust stains mean your metal valley flashing is corroding from underneath. That's a sure sign the valley needs replacement soon.
What to look for from the ground
Grab binoculars and check your valleys from your yard. Don't climb up there yourself.
Damaged shingles in the valley mean trouble. Missing shingles, curled edges, cracks, or shingles that look darker because they lost their granules. If the shingles look crooked or out of line, someone probably installed them wrong.
Metal valley flashing shows rust, holes, or thin spots when it fails. The seams between sections pull apart. Sometimes the whole thing lifts away from the roof.
Heavy debris piled in your valley means water isn't draining right. That debris creates a dam and water backs up under your shingles. Its accelerating the deterioration right now, even if you don't see a leak yet.
Bad installation shows from the ground too. Uneven valley edges where shingles got cut wrong. Valleys that change width as they run down. Shingles pointing the wrong direction. All signs of poor workmanship that will leak eventually.
Test for hidden leaks
If you suspect a leak but can't confirm it, you have options. Have someone sit in the attic during the next rainstorm and watch the valley area. They'll see exactly where water comes in.
A roofing contractor can run a hose test. They spray water down the valley from the roof and watch for leaks inside. Some add harmless colored dye to the water so its easier to trace where the leak travels.
Common valley failure types
Valleys fail in different ways. Knowing what's wrong helps you understand what the fix will involve.
Corroded metal flashing
Metal valley flashing eventually rusts through. Galvanized steel lasts 20 to 30 years before rust takes over. Aluminum can last 30 to 40 years, but it corrodes faster when it touches other types of metal. Cheap thin-gauge flashing fails even quicker.
Look for rust stains running down from the valley. Visible holes or thin spots in the metal. Corrosion eating away at the edges. When metal fails, you need complete flashing replacement with better material like aluminum, stainless steel, or copper.
Separated flashing seams
Long valleys need multiple sections of flashing. Those sections should overlap by at least 12 inches and get sealed with roofing cement. But thermal expansion and contraction constantly pull at those seams. Sometimes the installer skipped the sealant entirely. Sometimes the sealant just fails after years of temperature swings.
Water sneaks in at separated seams and flows straight onto your roof deck underneath. If the flashing otherwise looks good, a roofer can clean and reseal the seams. Extensive separation means you need new flashing.
Ice dam damage
This one hits Ontario homes hard. Snow melts on your warm roof and runs down to the cold valley. It refreezes there and builds up into a solid ice dam. More meltwater backs up behind that ice wall and gets forced sideways under your shingles.
Ice dams lift your shingles, separate the flashing, and saturate the underlayment. You'll need to fix the immediate valley damage, but you also need to address why ice dams form in the first place. That means improving your attic insulation and ventilation.
Debris dams
Leaves and twigs wash down your roof and pile up in the valley. Shingle granules add to the mess. Eventually you get a debris dam that blocks water flow. Water pools behind the dam and seeps under your shingles.
Trees overhanging your roof make this worse. Low-slope valleys drain slower and collect more debris. Clogged gutters at the valley bottom compound the whole problem.
Fix requires cleaning the valley, repairing any damage, trimming back trees, and probably installing gutter guards.
Bad shingle installation
Valley shingling takes skill. Shingles should stop two to four inches from the valley center, not extend into it. Cuts need to be straight and precise. Each shingle needs proper sealant. The underlayment needs to run the full valley length.
Sloppy work leaves gaps where water channels underneath. Shingles pointing the wrong direction funnel water toward the seams instead of away from them. When installation is the problem, the only fix is tearing out those shingles and doing it right.
Poor underlayment
Building code requires extra underlayment protection in valleys. A single layer of felt paper isn't enough. Ontario valleys should have ice and water shield running their full length.
Old roofs often have inadequate underlayment because standards were different back then. Or the underlayment deteriorated with age. Sometimes there are gaps in coverage. Whatever the cause, you need to remove the valley materials, install proper underlayment, then rebuild the valley.
Closed valley failure
Closed valleys look cleaner but they're weaker. They rely completely on shingles with no metal backup. Shingle seams sit right in the highest-flow area on your roof. When those shingles fail, water pours straight through.
Closed valleys typically fail five to ten years sooner than open metal valleys. If you have a closed valley leaking, convert it to an open metal valley during the repair. You'll get much longer life out of it.
Structural damage
Long-term valley leaks rot the roof deck and valley framing underneath. You'll see the valley sagging from the ground. It feels soft or spongy if you walk near it. Up in the attic, the wood looks dark and crumbly.
Structural repairs get expensive because the roofer needs to replace damaged deck sections and possibly valley framing boards before they can even install new flashing. But skip this step and your new valley will fail just as fast as the old one.
Emergency response steps
Valley leaks dump more water than regular roof leaks. Act fast to limit the damage.
Contain the water immediately
Get buckets under any active drips. Throw down towels and tarps to protect your flooring and furniture. Move anything valuable away from the wet area.
If water's really pouring in, grab a wet-dry vacuum. And if water's anywhere near electrical outlets or light fixtures, shut off the power to those circuits right now.
Check your attic
Carefully get up into the attic and look around. Check how much water accumulated. Try to spot where its coming in. You might need to put containers up there too if water's pooling.
Take photos and video of everything you see. You'll want this documentation later for insurance or to show the roofer.
Document all the damage
Photograph every stain, every wet spot, every piece of damaged ceiling. Video the active leak if you can. Write down the date, time, and what the weather's doing outside.
Insurance companies want this documentation. Even if you don't file a claim, you'll have a record of what happened.
Call an emergency roofer
Emergency services cost $300 to $1,000 but they stop the leak today. A crew can tarp over the valley, apply a temporary patch, or clear debris dams causing water backup.
That emergency service fee is cheap compared to thousands in interior damage if you wait. Every hour water pours in costs you more money in repairs.
Start the drying process
Set up dehumidifiers in the affected rooms. Run fans for air circulation. Pull out wet insulation if you can reach it safely.
Don't seal up wet walls or ceilings. They need airflow to dry. Watch for mold growth - it starts in just 24 to 48 hours once things get wet.
Clear debris if you can do it safely
If you can reach the valley from a ladder without getting on the roof, pull out any obvious debris. Clear the gutter where it meets the valley. This might give you temporary relief until a pro can properly fix it.
Emergency service or regular appointment?
Call for emergency service if you have heavy water coming in during a storm, if the leak threatens your electrical system, or if more storms are coming before a regular contractor can get there. Large amounts of water or significant damage already happening means you need help now.
You can wait for a regular appointment if the leak is minor, the rain stopped, clear weather's forecast for the next few days, and you've got everything contained and drying. Just don't wait too long - valleys don't fix themselves.
Repair and replacement options
What your valley needs depends on how bad the damage is, how old it is, and what condition the rest of your roof is in.
Minor repairs and resealing
If your flashing is still solid but the seams pulled apart, a roofer can clean everything and reseal those seams. They'll patch small holes if they can and secure any loose edges. This works for newer valleys with minor problems or when you just need to buy time until a full reroof.
Costs $200 to $500. Lasts three to seven years as a temporary fix.
Complete valley flashing replacement
When your flashing is corroded, leaking in multiple spots, or nearing the end of its life, you need full replacement. The roofer strips back shingles two to three feet on each side of the valley. Old flashing comes out. They inspect the deck underneath and fix any damage. Ice and water shield goes down the full valley length, then new metal flashing, sealed seams, and shingles reinstalled properly.
Material choices matter here. Aluminum is most common - runs 30 to 40 years and costs $400 to $1,200 per valley. Copper is premium, lasts 50-plus years, but costs $1,000 to $2,500. Stainless steel sits in the middle at 40 to 50 years. Skip galvanized steel because it rusts.
Convert closed valley to open metal
If your closed valley keeps failing, convert it to open metal during the repair. You get metal flashing as a secondary water barrier. Debris cleans out easier. The valley lasts longer and handles ice dams better.
Same process as flashing replacement. Costs $500 to $1,500 per valley. Worth it for the extra durability.
Valley replacement with ice dam protection
Ontario homes with ice dam problems need extra protection. This means ice and water shield extending three to four feet on each side of the valley. Heating cables installed right in the valley prevent ice formation. Plus improvements to your attic insulation and ventilation to stop the heat loss that causes ice dams in the first place.
Runs $600 to $2,000 per valley including the heating cables. But it eliminates ice dam valley leaks permanently, which is huge for Ontario winters.
Structural repair plus valley replacement
Long-term leaks rot your roof deck and valley framing. The roofer needs to remove damaged deck sections, replace or repair rotted valley framing boards, install new deck material, then proceed with the valley flashing work.
Costs $1,000 to $3,000 or more depending how extensive the rot is. You can't skip this - new flashing over rotten wood will just fail again fast.
Full roof replacement
If your roof's over 20 years old, or you have multiple failing valleys, or the overall condition is poor, consider replacing the whole roof. Makes sense when valley repair costs approach 30% of what a full replacement would cost.
Full reroof runs $8,000 to $18,000 for a typical Ontario home. Fixes all your valleys and every other roof issue at once.
What proper installation looks like
Good valley work starts with ice and water shield running the full valley length. Flashing should be at least 24 inches wide, made from rust-proof material. Sections overlap by 12 inches minimum with all seams sealed. Shingles stop two to four inches from the valley center and get properly sealed. No nails in the valley center where water flows.
Repair costs in Ontario
Valley repairs range from a few hundred bucks to several thousand depending on what needs fixing and what materials you choose.
Emergency services
Emergency service call fees run $150 to $300. Tarping over the valley costs $300 to $800. A temporary valley patch runs $200 to $500. These are stop-gap measures until proper repair.
Permanent repair costs
Minor Flashing Repair/Resealing
$200 - $500
Clean valley; reseal seams; patch minor issues; temporary fix
Valley Flashing Replacement (Short Valley)
$400 - $800
Under 15 feet; aluminum flashing; basic installation; most common repair
Valley Flashing Replacement (Long Valley)
$800 - $1,500
15-30 feet; aluminum or stainless; includes ice & water shield
Copper Valley Installation
$1,000 - $2,500
Premium material; 50+ year lifespan; best long-term value
Valley with Ice Dam Protection
$800 - $2,000
Enhanced underlayment; heating cables; insulation improvements
Structural Repair + Valley
$1,200 - $3,500
Replace damaged deck/framing; depends on damage extent; includes valley replacement
Multiple Valleys
$1,500 - $5,000
Most homes have 2-4 valleys; efficiency savings replacing multiple simultaneously
Other costs to consider
Interior damage repair can hit $500 to $3,000 or more depending how bad the water damage got. Mold remediation runs $1,000 to $3,000 for significant growth. Replacing wet insulation costs $300 to $1,000 for the affected areas. If the valley leak damaged your gutters you're looking at $400 to $1,200 for gutter replacement.
What drives the price up or down
Long valleys over 30 feet cost more. Multiple valleys need more work. Steep roof pitch makes access harder and labor more expensive. Premium materials like copper versus aluminum add to the bill. Structural repairs push costs higher. Ice dam protection systems add expense. Complex roof designs take more time. Winter repairs are tougher and pricier.
Save money by doing multiple valleys at once. Bundle valley work with other roof repairs. Schedule during off-season like late fall or early spring when contractors are less busy. Choose aluminum over copper - its adequate for most homes and costs way less.
Will insurance cover it?
Insurance usually covers sudden valley failure from storm damage, ice dam damage if you maintained your roof properly, and interior damage resulting from a covered roof failure.
They won't cover age-related deterioration, lack of maintenance, pre-existing problems, or improper installation from whenever your roof was first done.
Preventing valley leaks
Most valley leaks are preventable. Basic maintenance catches problems before they turn into expensive repairs.
Clean your valleys twice a year
Pull out leaves, twigs, shingle granules, moss, and any other debris that builds up. Spring and fall are the minimum. If trees overhang your roof, clean more often.
Hire a pro for this - its safer. Only try DIY if you can reach the valley safely from a ladder without getting on the roof. Costs $100 to $200 as part of a roof cleaning and inspection. Prevents the debris dams that cause 80% of valley leaks.
Get an annual roof inspection
A professional checks your valley flashing condition, shingle integrity around the valleys, sealant condition, debris buildup, ice dam damage from the previous winter, and any rust or corrosion developing.
Runs $150 to $300 once a year. Catches small $200 to $500 repairs before they turn into $1,000 to $3,000 disasters.
Manage your trees
Trim branches back so they don't overhang your roof. Keep at least six to ten feet of clearance. Remove dead trees. Prune annually. If a tree constantly dumps debris on your valleys, think about taking it out entirely.
Annual tree trimming costs $200 to $800. Dramatically cuts down on debris accumulation and related valley problems.
Keep your gutters clean
The valley-gutter connection is where water exits your roof. Clean gutters twice a year, especially where valleys discharge into them. Make sure gutters slope properly toward downspouts. Fix separated or damaged sections. Install gutter guards to cut down on cleaning frequency.
Clogged gutters back water up into your valleys. That's a recipe for leaks.
Stop ice dams before they start
Ice dams love Ontario valleys. Your attic needs proper insulation - R-50 minimum to keep heat from escaping to your roof. Balance your ventilation with soffit and ridge vents so the roof stays cold. Install heating cables in your valleys to prevent ice formation. After big snowstorms, remove heavy snow from roof edges and valleys.
Insulation and ventilation improvements cost $500 to $2,000 up front. Eliminates ice dam valley leaks permanently. Worth every penny in Ontario.
Design valleys right during roof replacement
When you replace your roof, insist on open metal valleys - they're way more durable than closed valleys. Ice and water shield should run the full valley length. Use rust-proof flashing materials. Flashing needs to be at least 24 inches wide. Never reuse old valley flashing even if it looks okay.
Fix small problems immediately
Valleys handle so much water that small problems escalate fast. A tiny gap becomes a major leak in months. Valley leaks cause rapid structural damage because of the water volume. A $300 repair today stops a $2,000 repair next year.
Pick the right material
Aluminum works well for most homes. Lasts 30 to 40 years and costs $400 to $800 per valley. Stainless steel is better at 40 to 50 years but costs more. Copper is best - over 50 years lifespan but runs $1,000 to $2,500 per valley. Skip galvanized steel because it rusts out in 20 to 30 years.
If you're staying in your home for 15-plus years, copper actually breaks even on cost and gives you superior longevity.
Frequently asked questions
Why does my roof only leak in the valley during heavy rain?
Your valley handles two to three times more water than the rest of your roof. Small gaps in the flashing or minor shingle problems don't leak during light drizzle. But when a heavy storm hits, the water volume overwhelms your valley's compromised capacity and pours through.
This tells you the valley is on the edge of complete failure. Get it fixed now before it gets worse - and it will get worse.
How much does valley flashing replacement cost in Ontario?
Short valleys under 15 feet run $400 to $800. Long valleys from 15 to 30 feet cost $800 to $1,500. Copper valleys are premium at $1,000 to $2,500. If you're doing multiple valleys at once, expect $1,500 to $5,000 total.
Price depends on valley length, materials you pick, roof pitch, whether structural repairs are needed, and what time of year you do the work.
Should I choose open metal valley or closed valley?
Open metal valley is better for Ontario homes. It lasts 30 to 50 years versus 20 to 30 for closed valleys. Easier to clean debris out. Better ice dam resistance. Metal provides a secondary water barrier. Repairs are simpler too.
Downside is open valleys cost $200 to $400 more and you see the metal flashing. Only go with closed valley if looks are super important to you and you're okay with shorter lifespan and more maintenance.
How long does valley flashing last?
Depends what its made from. Galvanized steel rusts out in 20 to 30 years. Aluminum lasts 30 to 40 years. Stainless steel goes 40 to 50 years. Copper runs 50-plus years.
Ontario's freeze-thaw cycles, heavy debris, poor installation, and lack of maintenance all shorten lifespan. A well-maintained aluminum valley in Ontario typically makes it 30 to 35 years.
Can I repair valley myself or do I need professional?
Get a professional for most valley work. Roof access is dangerous. Proper flashing installation takes real skill. Its integrated with your shingles in complex ways. Mistakes create leaks worse than what you started with. Plus DIY work can void your insurance if something goes wrong.
You can clean debris from the valley yourself if you can reach it safely from a ladder. Same with clearing gutters where the valley drains. But don't try to install flashing, remove shingles, or do structural repairs on your own.
Are ice dams causing my valley to leak?
Maybe - ice dams are super common in Ontario valleys. Signs include leaks during winter or spring thaw, icicles forming in the valley, heavy snow on your roof before the leak started, and inadequate insulation or ventilation when you check the attic.
If ice dams are the culprit, you need to repair the immediate valley damage, fix the underlying insulation and ventilation issues, maybe add heating cables to your valleys, and install enhanced ice barrier when you replace the valley.
How often should I clean my roof valleys?
Minimum twice a year in spring and fall. If you have trees near your house bump it to three or four times yearly. Also check after major storms for debris pileup.
Costs $100 to $200 as part of professional roof cleaning and inspection. Prevents 80% of valley leak problems and makes your valley last way longer.
Is valley leak covered by insurance?
Depends why it leaked. Insurance usually covers sudden failure from a storm, ice dam damage if you maintained your roof properly, and wind damage.
They won't cover age-related deterioration, lack of maintenance, pre-existing problems, or bad installation from years ago.
To get coverage, document that you maintained the roof, connect the leak to a specific damaging event, and report it right away.
Should I replace valley if rest of roof is old?
If your roof's over 15 years old, think hard about replacing the whole thing. Valley replacement costs $800 to $1,500. But if your roof needs replacing within five years anyway, you're paying for that valley twice - once now and once during the reroof. Makes more sense to do everything at once.
Exception is if your roof's under 10 years old with lots of life left. Then valley replacement alone makes perfect sense.
What's the best valley flashing material for Ontario?
Aluminum offers the best value for most homeowners. Costs $400 to $800 per valley, lasts 30 to 40 years, doesn't rust, and handles Ontario's climate well.
Copper is premium at $1,000 to $2,500 per valley but lasts 50-plus years. Great choice if you're staying in the home long-term. Stainless steel sits in the middle at $600 to $1,200 and 40 to 50 years.
Skip galvanized steel - it rusts fast in Ontario's wet climate and doesn't last.
Valley Leaking on Your Roof?
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