Oil canning on a metal roof is the visible waviness or rippling in the flat area of a panel, usually seen at low sun angles. It is cosmetic, it is inherent to thin sheet metal, and manufacturers exclude it from most warranties. It is also largely preventable. Striated 24-gauge panels in a narrow width, tension-leveled coil, floating clips and a flat deck are how Architectural Metal Panels keeps it faint enough that nobody notices from the street.
Here is what causes it on Dallas-Fort Worth roofs and wall panels, why it is not a defect, what we do to reduce it, and how to judge a sample in sunlight before you choose a panel.
What is oil canning?
Oil canning is a slight buckling of the flat part of a metal panel, the pan between the seams or ribs, that shows up as waves, ripples or a bellied look. The name comes from the way the bottom of an old oil can pops in and out. On a roof it is most visible when the sun is low and raking across the surface, and it often comes and goes with temperature through the day.
The important part is what it is not. It is not a leak path, a loose panel or a sign the roof is failing. The seams, clips and flashings that keep water out sit at the edges of the pan, and they do their job whether the pan is perfectly flat or not. Industry guidance treats oil canning as an inherent characteristic of light-gauge cold-formed sheet rather than a reason to reject a panel.
What causes oil canning?
Usually several small things at once. A flat sheet of thin steel has almost no stiffness across its width, so any stress that is not perfectly even shows up as a wave. The stress can come from the mill, from the installer or from the sun.
- Coil stress from the mill. Steel coil arrives with residual stress from rolling. Edge wave, center buckle and camber are locked into the sheet before it reaches the roll former, and they come out as ripples once the panel is cut and laid flat.
- Over-driven fasteners and pinned clips. A clip screw driven too hard dimples the panel leg and pulls the pan tight around it. A panel that cannot move is a panel under stress.
- Uneven substrate. A deck with high spots, a purlin out of plane or an old roof left under the new one forces the panel to bridge dips and ride humps. Metal copies whatever it sits on.
- Restrained thermal movement. A 40-foot steel panel typically grows and shrinks roughly half an inch across a Texas temperature swing. If clips or trim will not let it, the pan buckles instead.
- Wide, flat pans. The wider the flat area, the less stiffness it has. An 18- or 20-inch flat pan oil cans far more than a 12- or 16-inch striated one.
- Dark, glossy colors and low sun. A dark, shiny pan mirrors the sky, so every ripple shows as a change in reflection. Early morning and late afternoon light makes it worst.
- Roll-former and handling issues. Misaligned forming rolls or panels carried flat and allowed to flex add stress that the pan remembers.
Why is oil canning cosmetic and excluded from warranties?
Because it changes how a roof looks, not how it performs, and because no manufacturer can control the installer’s deck, clips or panel choice. Manufacturer finish and substrate warranties typically exclude oil canning outright, and industry technical bulletins state that it is not grounds for rejection. Workmanship warranties in the trade usually follow the same line.
That is also true of our lifetime workmanship warranty: it covers the installation keeping water out, which oil canning does not affect. Where we differ is up front. We design the roof to minimize it, we put the panel, gauge and profile in writing, and we show you a sample in the sun before we order coil, so there are no surprises on the first low-sun evening.
One related point: insurance cosmetic-damage exclusions are about hail dents, not oil canning, and a wavy pan is not storm damage. If a roof develops new waviness years after installation, the cause is usually a moving deck or a failed clip, which is worth an inspection.
How does Architectural Metal Panels reduce oil canning?
By stacking every lever that stiffens the pan or relieves stress, rather than relying on one. No single choice eliminates oil canning, but together they make it hard to find.
| Technique | What it does | Where we use it |
|---|---|---|
| Striations or pencil ribs in the pan | Stiffen the flat and break up the reflection so the eye cannot read a continuous surface; the single biggest reduction | Standard on our residential standing seam |
| Narrower panels (12 to 16 inch) | Less unsupported flat between seams, so less room to wave | 16 inch is our default; 12 inch on highly visible or dark roofs |
| 24-gauge steel | Roughly 30% thicker than 26 gauge, so the pan holds flatter and dents less | Standard tier; 26 gauge offered as a value option with the trade-off explained |
| Tension-leveled coil | Coil run through a leveler at the supplier to pull out mill stress before forming | Specified on every coil order for flat or lightly striated profiles |
| Floating clips and correct spacing | Let the panel expand and contract without stressing the pan; spacing follows the tested assembly | All long runs and all mechanical seam work |
| Flat decking | Straightedge and string-line check of the deck; shim, plane or re-sheath high and low spots before underlayment | Every re-roof, especially over older decks |
| Fastener torque | Clip screws set snug, never over-driven, so the panel leg is not dimpled or pinned | Crew standard on every job |
| Low-gloss finishes and lighter colors | Satin Kynar 500 scatters light and hides waviness that gloss would reveal | Recommended when the roof is dark or highly visible |
Gauge and finish each have their own guide: see 24-gauge vs 26-gauge metal roofing for the thickness trade-offs and Kynar 500 vs SMP for gloss and color retention. Clip behavior on long runs is covered in snap-lock vs mechanical seam standing seam.
What should you expect on wall panels and ACM?
Wall panels show oil canning more readily than roofs because they sit vertical, at eye level, in side light for much of the day. A flat, flush wall panel in a dark color is the hardest case in the trade. Ribbed and wave profiles are the answer: a rib every few inches stiffens the sheet and casts its own shadow line, so there is no long flat for the eye to read.
That is why our concealed-fastener AMP Wave 16-4 wall panel carries four waves across its 16-inch coverage, and why the 12-inch AMP Wave 12-3 and the 7.2 rib profile exist for walls that need an even stiffer surface. On storefronts and modern homes where a flush look is wanted, we steer toward 22- or 24-gauge steel, narrower modules and satin finishes, and we say plainly that some waviness in side light is normal. The full line is on our metal wall panels page.
Aluminum composite material (ACM) behaves differently. Two thin aluminum skins bonded to a core, typically 4 mm overall, make a panel that is flat and stiff by design, so classic oil canning is rare. What ACM can show instead is dimpling or pillowing: a slight bulge at each attachment point or across a panel that was fabricated or fastened too tight for thermal movement. Proper rout-and-return fabrication, correct fastener spacing and a flat substructure keep aluminum composite panels looking like glass.
How do you judge a sample in sunlight?
Look at a full-width, full-length sample in the light the roof will actually live in, not a 6-inch color chip in a showroom. Ten minutes on your driveway tells you more than any brochure:
- Ask for a sample at least 3 feet long in the exact profile, gauge, color and finish you are considering, plus a striated version of the same panel if you are looking at a flat pan.
- Hold it at your roof’s pitch and orient it the way the panels will run, seams up and down the slope.
- Look at it in low sun, early morning or late afternoon, with the light raking across the pan. Midday sun flatters everything.
- Step back to street distance. Waviness you can see from 2 feet and not from 40 feet is waviness nobody will notice on the roof.
- Compare dark against light and gloss against satin in the same light. The difference is usually bigger than people expect.
- Ask to see a finished roof in your profile and color, and drive by it late in the day. We can point you to standing seam roofs across east Dallas-Fort Worth, from Forney to Rockwall.
What this means for DFW homeowners
Every metal roof oil cans a little, and a good one oil cans so little you have to hunt for it. If a contractor promises none, be skeptical; if a contractor shrugs and says it is normal without explaining how they limit it, be more skeptical. The right answer is a striated 24-gauge panel in a sensible width, run from tension-leveled coil, set on floating clips over a flat deck, with a sample in your hand in afternoon light before you sign.
Oil canning: frequently asked questions
Is oil canning a defect?
No. Industry guidance and manufacturer literature treat oil canning as an inherent characteristic of light-gauge cold-formed metal, not a defect and not a reason to reject panels. It does not affect the panel’s ability to shed water, resist wind or take hail. That said, a roof that oil cans badly often reveals a decision that could have gone better: a wide flat pan, a thin gauge, a wavy deck or over-driven fasteners.
Will oil canning cause leaks?
No. The waviness lives in the flat of the panel, well away from the seams, clips and flashings that keep water out. A panel can look wavy and be perfectly tight. If you have a leak on a metal roof, look at penetrations, flashing and fastener condition, not at the oil canning.
Can oil canning be fixed after the roof is installed?
Rarely, and usually not completely. If a specific cause can be found, such as an over-driven clip screw, a pinned panel that cannot move or a high spot in the deck, correcting it can reduce the waviness. Waviness that comes from coil stress or a wide flat pan is in the metal itself, and the only real fix is replacing those panels with a striated or narrower profile.
Does a striated panel eliminate oil canning?
It reduces it more than any other single choice, but nothing eliminates it entirely. Striations and pencil ribs stiffen the pan and break up the reflection so the eye no longer reads a continuous surface. On a 24-gauge, 16-inch striated panel over a flat deck, oil canning is typically faint enough that nobody notices it from the ground.
Which colors show oil canning the most?
Dark, glossy colors on long flat pans in low sun. Black, charcoal and dark bronze act like a mirror for the sky, so every ripple shows as a change in reflection. Lighter colors and satin finishes such as Kynar 500 scatter light and hide the same waviness. If you want a dark roof, pair it with striations and 24-gauge steel.
Does oil canning affect my warranty?
Manufacturer finish and substrate warranties typically exclude oil canning outright, and so does most workmanship coverage, because it is cosmetic. Our lifetime workmanship warranty covers the installation keeping water out. What we do instead is design it out up front, and we put the panel, gauge and profile choices in writing so you know what to expect before we order coil.
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Sources
References checked October 2026. Warranty exclusions and the “not grounds for rejection” position come from manufacturer published data and industry technical bulletins on oil canning:
- Sheffield Metals learning center: panel profiles — oil canning as an inherent characteristic and the role of striations, width and gauge
- RoofersCoffeeShop: snap-lock versus mechanical seam — clip spacing, substrate flatness and finish gloss in oil canning
- McElroy Metal: Kynar 500 vs SMP paint systems — gloss and finish differences that affect visibility
- Texas Department of Insurance bulletin on cosmetic hail damage — how cosmetic exclusions are defined (hail dents, not oil canning)
- The Dallas Morning News: January 2024 freeze — the temperature swing behind thermal movement in North Texas
See a sample in your own sunlight
We bring striated and flat samples in your color, check your deck, and write the panel, gauge, clip and coil spec into the estimate. Call (469) 569-3956 or request a free quote online.
