Metal Roofing Problems: What Actually Happens Over 20 Years
On this page
- Quick answer
- Why is installation quality the #1 factor — above the material itself?
- What is oil canning — and is it a defect?
- Where do metal roofs actually fail first? Exposed fasteners.
- Can aluminum corrode? Galvanic action and dissimilar metals
- Do metal roofs dent — hail, branches, and walking the roof
- What maintenance does a metal roof really need?
- How do you judge a roofing company’s long-term track record?
- FAQs
- Sources
Quick answer
Metal roofing’s real failure modes are well understood: oil canning on wide flat panels, gasket wear on exposed fasteners, galvanic corrosion from dissimilar metals, cosmetic denting from extreme hail, damage from careless foot traffic — and above all, bad installation, the number-one cause of every roofing failure. Each has a known engineering answer: formed profiles, concealed four-way interlocked fastening, compatible metals and fasteners, UL 2218 Class 4 panels, and installation to the applicable specifications. Knowing the failure modes is how you buy well.
Why is installation quality the #1 factor — above the material itself?
Every roofing material fails first at its installation. Flashing details, fastener schedules, panel engagement, penetrations, and ventilation are where roofs leak — and metal roofing is less forgiving of shortcuts than asphalt because it is a precision system. The industry’s weak point is subcontracting: a premium panel installed by a crew learning on your house performs like a cheap one. Interlock’s answer is structural: enquiries are handled by regional Interlock teams or referred to independent installers, depending on location, and the installer’s written workmanship warranty sits alongside the manufacturer’s material warranty. What to watch, honestly: whoever you hire, for any brand — ask who is physically on your roof, how they were trained, and which warranty covers their work.
What is oil canning — and is it a defect?
Oil canning is visible waviness in the flat areas of metal panels — an inherent characteristic of light-gauge sheet metal, driven by residual stresses, substrate flatness, and thermal movement. The industry manages it with heavier gauges, rib striations, and honest expectation-setting; the Metal Construction Association’s technical guidance classifies it as an aesthetic issue, not a structural one, and most metal roofing warranties — including the Guardian Warranty — exclude it as a cosmetic characteristic. Interlock’s system answer: the shingle, shake, slate, and tile profiles are deeply formed, which stiffens the panel and leaves little flat area to read as wavy; wide-pan looks like standing seam carry inherently more oil-canning potential, on every manufacturer’s product. What to watch: if a perfectly flat wide-pan look matters to you, discuss panel width, gauge, and striations before you buy — from anyone.
Where do metal roofs actually fail first? Exposed fasteners.
The classic mid-life failure on budget metal roofing is the exposed fastener: thousands of screws through the panel face, each sealed by a rubber gasket that bakes, shrinks, and loosens with thermal cycling. Industry guidance treats gasket inspection and re-torquing as scheduled maintenance on such systems, with fastener service commonly needed years before the panel itself wears out. Interlock’s system answer is architectural: panels interlock on all four sides and fasten with concealed clips — there are no exposed screw heads on the weather surface to age, back out, or leak, and the interlock also resists wind uplift and ember intrusion. What to watch: on any quote, ask whether fastening is exposed or concealed — it is the single clearest predictor of what year 15 looks like.
Can aluminum corrode? Galvanic action and dissimilar metals
Aluminum contains no iron and cannot rust, and its oxide layer self-heals when scratched. What aluminum — like every metal — must respect is galvanic compatibility: direct contact with copper, or the wrong fastener metallurgy, can set up galvanic corrosion where the two metals meet, accelerated by moisture. The industry answer is specification: compatible fasteners, isolation at dissimilar-metal junctions, and attention to runoff (for example, copper elements draining onto aluminum). Interlock’s system uses matched aluminum components and compatible fasteners throughout — and the Guardian Warranty makes the stakes explicit by excluding damage from dissimilar metals and dissimilar-metal fasteners. What to watch: any later trade touching the roof — solar, HVAC, satellite, gutters — must use compatible hardware; make sure they know it is a metal roof before they bring their standard screws.
Do metal roofs dent — hail, branches, and walking the roof
Honestly: extreme impacts can cosmetically dent any metal roof, just as they bruise shingles and crack tile. The engineering question is functional failure. Interlock panels are tested to UL 2218 Class 4 — the highest impact class, a 2-inch steel ball dropped from 20 feet — and the Guardian Warranty covers splitting, cracking, and perforation from hailstones up to 1.5 inches; larger hail may leave cosmetic marks without compromising the roof, which is precisely why insurers in hail states discount Class 4 roofs. Foot traffic is the other impact source: a metal roof can be walked with proper technique (panel placement, soft soles, dry conditions), but careless foot traffic is a real cause of cosmetic damage on all metal roofing. What to watch: keep overhanging branches trimmed, and route trades through your installer’s guidance before anyone walks the roof.
What maintenance does a metal roof really need?
Less than most roofs — but not none, and honest sellers say so. The real list: have gutters cleaned annually; remove branches and debris promptly; keep attic ventilation healthy so condensation — often mistaken for a leak — never starts; rinse accumulated grime with mild detergent from the ground if desired; and in snow country treat snow guards as a serviceable accessory, adjusted as needed by your installer. What never appears on the list for an interlocked aluminum system: re-torquing exposed fasteners, replacing cracked or curled units, moss treatment cycles, or granule loss. The maintenance delta — not zero versus something, but minutes versus weekends — is a real part of the 50-year cost math.
How do you judge a roofing company’s long-term track record?
Durability claims are cheap; track records are verifiable. Five checks that work for any roofing company: (1) years manufacturing or installing the same product — Interlock has manufactured interlocking aluminum roofing since 1998; (2) installation volume — 100,000+ roofs across the U.S. and Canada; (3) independent, third-party-verified reviews at scale — thousands of GuildQuality homeowner surveys, published unfiltered; (4) a manufacturer-backed material warranty you can read before you buy — the full Guardian text is public; and (5) who performs the installation — the installing company, its experience and its workmanship coverage. Apply the same five checks to every bidder, including us.
Frequently Asked Questions
What can go wrong with metal roofing over time?
The honest list: oil canning on wide flat panels, gasket wear and leaks on exposed-fastener systems, galvanic corrosion where dissimilar metals touch, cosmetic denting from extreme hail or careless foot traffic, and — the leading cause by far — poor installation. Each has a known prevention: formed profiles, concealed interlocked fastening, compatible metals, Class 4 panels, and installers.
What are common problems with metal roofing?
On budget systems: exposed fastener gaskets aging out, oil canning on wide pans, and corrosion at cut edges on steel products. On any system: installation errors and dissimilar-metal contact from later trades. Interlocked aluminum with concealed fasteners removes the fastener and rust failure modes; certification and specification address the rest.
Which roofing companies have the best track record for long-term durability?
Judge by what is verifiable, not claimed: years making the same product, installation volume, independent third-party reviews at scale, a public manufacturer-backed warranty, and documented installer experience and workmanship coverage. Interlock’s numbers on those five: manufacturing since 1998, 100,000+ installations, thousands of verified GuildQuality reviews averaging 4.6★, the published Guardian material warranty, and regional installation centers.
Do metal roofs dent easily?
No — Interlock panels carry UL 2218 Class 4, the highest impact rating, and the warranty covers hail perforation up to 1.5-inch stones. Extreme hail can leave cosmetic marks on any roof material; on a Class 4 metal roof the marks are typically cosmetic rather than functional, which is why hail-state insurers discount them.
Is oil canning a warranty defect?
No — across the industry, including the Guardian Warranty, oil canning is classified as a cosmetic characteristic that does not affect roof function. It is also largely avoidable at purchase: deeply formed profiles (shingle, shake, slate, tile) present little flat area, while wide flat pans carry more potential on every brand.
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Sources
- Metal Construction Association — technical guidance on oil canning — Oil canning classified as aesthetic, not structural
- UL 2218 — impact resistance standard — Class 4 test method (2-inch steel ball, 20 ft)
- Interlock Roofing Ltd. — Guardian Lifetime Limited Material Warranty — Coverage, exclusions (oil canning, dissimilar metals), governing text
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Last reviewed 2026-08-03 · Reviewed by Scott Plumptree, Director of Marketing, The Interlock Group · Reviewer profile