Fishmouthing is when the middle of an asphalt shingle tab lifts and curls upward, leaving an open, mouth-like gap along the edge. On a roof that is more than a few years old, it usually means the shingles are drying out and moving more than they should, often with moisture or attic heat in the mix. It is not always an emergency. It is a sign to get the roof looked at before storm season decides the timing for you.
We are Shingle Roof Renewal, and we work on aging asphalt shingle roofs in Broward and Palm Beach County. Here is how to recognize fishmouthing, what causes it, what it can lead to, and what your options are.
TL;DR
- Fishmouthing is an upward curl in the body of a shingle tab, not just at the corners. It is a distortion pattern, and on older roofs it points to age, moisture or poor attic ventilation.
- Do not confuse it with a fishmouth in flat-roof membrane. The word is the same, but the cause and the fix are different.
- In Florida, UV and heat make shingles brittle faster, so distortion deserves a prompt professional look.
- Whether a roof can be preserved or needs replacing depends on how much cracking, granule loss and lifting there is. We inspect and tell you honestly.
- Call us before you call the roofer. The roof assessment is free.
Table of Contents
- What fishmouthing looks like on asphalt shingles
- Fishmouthing, curling, cupping, clawing and buckling
- What causes shingles to fishmouth
- Why South Florida roofs are especially exposed
- Can fishmouthing cause leaks?
- How to check your roof safely
- What are your options?
- How we approach it
- Get your roof looked at before storm season
- FAQ
- Sources
What fishmouthing looks like on asphalt shingles
Picture the tab of a three-tab or architectural shingle. Instead of lying flat, the center of the tab rises, and the edges on either side stay lower. Looked at from the side, the gap resembles the open mouth of a fish, which is where the name comes from.
Home inspectors use the term loosely. The national inspectors' association InterNACHI says that alligatoring and fishmouth are general terms for extreme shingle distortion once the shingles reach an advanced stage of deterioration. It also recommends that inspection reports describe distortion as minor, moderate or extreme. That is a helpful way to think about your own roof: it is a matter of degree.
Fishmouth on a flat roof is a different thing
Search results for this term mix two problems. On low-slope roofs with felt or membrane layers, a fishmouth is a small funnel-shaped opening at the edge of a ply or seam. The Canadian Roofing Contractors Association notes that these openings, if left unrepaired, expose the felts to the weather or let moisture in. Another industry article explains that a wrinkle reaching a membrane edge leaves a fishmouth-shaped opening that can act as a tunnel for water.
If your home has a pitched asphalt shingle roof, you are dealing with the shingle version. The rest of this article is about that.
Fishmouthing, curling, cupping, clawing and buckling
These words get used interchangeably, and that causes confusion when you are talking to a contractor. Here is a practical way to separate them.
| Term | What you see | Where the lift happens |
|---|---|---|
| Fishmouthing | Upward curve in the middle of a tab, with a gap at the edge | Body of the tab |
| Curling | Corners of the tab turn up | Tab corners |
| Cupping | Edges rise and the center looks concave | Perimeter of the tab |
| Clawing | Edges curl down while the center bows up | Center, with edges down |
| Buckling | Waves or ridges that run across the roof | Across shingles, often along deck joints |
The terms overlap in the field, and some roofers call any lifting curl. What matters is the pattern across the roof. Random lifting on a handful of shingles points one way. The same distortion repeated across a whole slope points another.
Buckling has its own causes
Waves that follow lines in the roof are often not a shingle-aging problem at all. A technical bulletin from the Asphalt Roofing Manufacturers Association says buckling can show up on new roofs and reroofs and is most often caused by wrinkles in the underlayment or movement of the wood decking. When moisture is involved, the distortion tends to line up with the joints between deck panels. If the waves appear within days of an install, that is a conversation to have with the installer.
What causes shingles to fishmouth
There is rarely one cause. Most cases come down to moisture moving in and out of the shingle, heat, and age.
Moisture and attic ventilation
Shingles take on moisture and release it. InterNACHI explains that shingles expand when they absorb moisture and shrink when they dry. The edges lose volatiles faster than the rest of the shingle, so they absorb and dry out more than the middle, and that uneven movement distorts the shingle. Over repeated cycles, the same source says, the edges can begin to delaminate.
An attic that traps heat and humidity makes this worse, because the underside of the roof sees more stress. We have written about this at length in our guides on attic ventilation and shingle life and a homeowner checklist for poor roof ventilation.
Age and a dried-out shingle
An asphalt shingle is held together by an asphalt binder. As it loses its natural oils, the shingle gets stiffer and less able to stay flat. A shingle that has gone brittle will not flex back into place the way a younger one does. This is the stage where we most often see fishmouthing on roofs in our service area.
Installation and handling
Nails driven too high or not flush, wet shingles installed from poor storage, and underlayment wrinkles can all produce lifting. If the distortion appears soon after a new roof goes on, installation is the first thing to check, and the shingle manufacturer's warranty terms are worth reading.
Why South Florida roofs are especially exposed
The Florida Division of Emergency Management's Hurricane Retrofit Guide explains that in Florida's hot, sunny climate, ultraviolet rays break down the asphalt that binds granules to the shingle, and heat bakes the shingles until they become brittle and lose strength. Broward and Palm Beach homes get that exposure for most of the year, with few cool months to give the roof a break.
Then there is the rain. Afternoon downpours wet the shingle, the sun dries it fast, and the cycle repeats. That is the exact wet-dry movement that distorts the edges. Add attic heat that has nowhere to go, and shingles age faster than the label on the bundle suggests. Our South Florida guide to why roofs fail prematurely covers this in more depth.
Can fishmouthing cause leaks?
Not always, and not on day one. A lifted shingle is not a hole. But it has a few effects worth taking seriously:
- A lifted tab can lose its seal. Once the seal strip lets go, the shingle is held down mostly by nails.
- Wind gets underneath. The Florida Building Commission's Hurricane Michael report notes that roof covering damage from high winds was a primary source of water intrusion, and cites a study of existing Florida homes that identified unsealed and partially unsealed shingles as sources of failure in high winds.
- Cracks follow. A distorted, brittle shingle cracks more easily when stepped on, hit by debris or flexed by wind.
So the honest answer is that fishmouthing is a warning sign. It is the roof telling you that something is changing, and the time to act is while the shingles are still in a condition that gives you choices.
How to check your roof safely
You do not need to climb up. In fact, please do not. Shingles that are brittle can crack under your weight, and a fall is a much bigger problem than a curled tab.
- Look from the ground in good light. Early morning or late afternoon, when the sun is low, makes shadow lines under lifted tabs easier to see. Binoculars help.
- Check the south and west slopes first. They get the most sun, and InterNACHI notes that distortion is often uniform across a slope rather than random.
- Look for companions. Granules collecting in gutters or at downspouts, bald patches, cracked tabs and exposed fiberglass are all signs of an aging roof. See our list of warning signs of shingle roof failure.
- Photograph what you see. Date-stamped photos make it easy to compare after the next storm.
- Peek in the attic if it is safe. Look for water stains on the underside of the deck, daylight where it should not be, and heat or stale air that feels excessive. If you are not comfortable going up there, skip it and mention it during the inspection.
- Note when it started. Distortion on a roof that is a few months old is a different conversation from distortion on a 15-year-old roof.
The Florida guide recommends that shingles be inspected at least once a year for signs of aging and weakness. It also lists cracked shingles, broken tabs, exposed fiberglass, bowed or cupped tabs and worn-off granules as signs that shingles are in need of replacement, because they will probably not stay on in high winds. That is exactly why a trained eye on your roof matters: how widespread these signs are decides what is possible.
What are your options?
The right move depends on the roof's age, how far the distortion has gone, and what the shingles are like when someone presses on them.
If the roof is new. Report it to your installer and to the manufacturer. Document it with photos. Installation and moisture issues are the usual suspects, and they are best resolved early.
If the roof is middle-aged and the shingles are still flexible. This is where preservation matters. Catching early distortion, granule loss and dryness before shingles crack can keep the roof in service for longer. Our guides on how to extend shingle life on an aging asphalt roof and preserving dried-out shingles in hot climates explain the thinking.
If the roof is old, cracked and shedding granules heavily. Some roofs are past the point of preservation, and we will tell you so. Knowing that early lets you plan and budget for replacement on your timeline, not after a storm.
Fix the cause too. If attic heat or humidity is a factor, ventilation needs attention from a qualified contractor, whatever you decide about the shingles. Spot repairs, like hand-sealing a few tabs, are a separate, small job and do not replace a conversation about the whole roof.
Check adhesion before you call anyone
A lifted tab often means the seal has let go. Our article on checking shingle adhesion before calling a roofer walks through what that means and why it matters before storm season.
How we approach it
We are not a roofing crew and we are not a roof cleaning service. We are a roof preservation company, certified as an applicator of Fresh Roof's Green Soy Technology. Our process is three steps:
- We inspect your roof.
- We assess its condition, including flexibility, granule loss, cracking and lifting.
- We tell you whether it qualifies for preservation and renewal.
Not every roof qualifies, and we say so when it does not. When a roof is a good candidate, our Green Soy treatment is designed to restore flexibility, slow deterioration and lock in granules. We back qualifying work with a 6-year transferable warranty. We also see it as the more environmentally responsible path when it works, since it avoids sending a whole roof to the landfill.
Our perspective
We get calls from homeowners who found a curled or fishmouthed tab, assumed the roof was finished and started collecting replacement quotes. Replacement can run $15,000 to $30,000, and for many of those homes the first step should have been an honest look at the shingles.
Here is how we see it. Fishmouthing is a symptom, and a symptom is information. It tells you the shingles have lost some of the flexibility they were made with. The earlier you learn that, the more options you keep. A roof that is still pliable and holding its granules is a very different case from one that is cracking and bare.
That is why we say call us before you call the roofer. A roofer sells replacement. We start by finding out if replacement is needed at all. When a roof qualifies, we can restore flexibility at a molecular level, lock in granules and help the shingles stand up to Florida sun, and homeowners may save up to 80% compared to a full replacement. When it does not, you hear that from us plainly and you can plan with real information.
Nobody knows this roof better than the sun and storms of Broward and Palm Beach County. We just help you read what they have been writing on it.
Daniellison
Get your roof looked at before storm season
If you can see lifted tabs, curling or granules in the gutters, the most useful next step is an inspection. We will check the roof, explain what we find, and tell you whether it qualifies for preservation.
Schedule a free roof assessment on our Shingle Roof Renewal homepage, or read how the service works on our services page.
We serve homeowners across Broward and Palm Beach County, including Boca Raton, Delray Beach and Plantation. Curious how our approach differs from standard rejuvenation products? See Fresh Roof vs. roof rejuvenation.
FAQ
Is fishmouthing the same as curling?
Not exactly. In fishmouthing, the lift is in the body of the tab. In curling, the corners turn up. Many roofers use the words loosely, so describe where on the shingle you see the lift and how widespread it is. That detail helps an inspector assess the roof.
Are fishmouthed shingles an emergency?
Usually not an emergency, but a reason to act soon. The shingle can lose its seal and become easier for wind to lift. If you also see cracks, missing granules or water stains inside, have the roof inspected promptly, especially ahead of hurricane season.
Can new shingles fishmouth?
Yes. On a new roof, the causes are typically moisture, how the shingles were handled or stored, or installation errors. Take dated photos, contact your installer, and ask about the manufacturer's warranty terms, which can exclude damage tied to inadequate attic ventilation.
Can a fishmouthed roof be preserved instead of replaced?
It depends on the condition of the shingles. If they are still flexible and holding granules, the roof may qualify for our preservation and renewal service. If they are cracked, brittle and bare, replacement may be the right call. A free inspection settles it.
Does Shingle Roof Renewal charge for the inspection?
No. The roof assessment is free. After the inspection, we tell you whether your roof qualifies and what the next step would be.
Sources
- InterNACHI: Mastering Roof Inspections, Asphalt Composition Shingles
- Asphalt Roofing Manufacturers Association: Plain Facts About Buckled Shingles
- Florida Hurricane Retrofit Guide: Shingle Roofs
- Florida Building Commission: Hurricane Michael best practices report
- Canadian Roofing Reference Manual: Potential Problem Areas
- Facilities Management Insights: Roof Failure, Effect and Cause