Metal roof leak repair starts with finding the exact source, then sealing that source with the right material. On an exposed-fastener metal roof, the leak is almost always a backed-out screw with a failed rubber washer, a separated panel seam, or worn flashing at a penetration. Fix the fastener with an oversize screw and a fresh EPDM washer, reseal a seam with butyl tape or metal-grade polyurethane, and reserve a full patch for actual holes. Chasing it with a bucket of generic silicone rarely holds.
This guide walks the diagnosis by source, then matches each failure to the correct sealant and fastener, with the specs and costs that most homeowner guides leave vague. For leaks on other roof systems, see our system-agnostic roof leak repair guide.
Why does a metal roof leak?
A metal roof leaks because the panels themselves rarely fail, but the fasteners, seams, and flashings that hold them together do. Steel expands and contracts across a wide daily temperature swing, and that movement works screws loose, cracks sealant, and separates laps over years. The panel is watertight. The thousands of holes drilled through it to attach it are the weak points.
On an exposed-fastener panel roof (through-fastened corrugated or R-panel), every screw is a potential leak. A standing seam roof hides its clips, so its leaks concentrate at seams, terminations, and flashings instead.
| Leak source | How common | Typical cause |
|---|---|---|
| Backed-out screw / failed washer | Most common on exposed-fastener roofs | Thermal cycling loosens the screw; UV degrades the rubber washer |
| Separated or unsealed seam | Common on both types | Old butyl tape shrinks; panel laps move apart |
| Flashing failure | Common at penetrations | Cracked sealant or bent metal at chimney, pipe, skylight, valley |
| Puncture or hole | Occasional | Hail, foot traffic, fallen branch, drilled-and-missed screw |
| Rust perforation | Older roofs | Coating wears through, then the steel corrodes at scratches and edges |
Why do metal roofs leak around screws?
Metal roofs leak around screws because the rubber washer under each screw head is the actual seal, and it fails before the screw does. When a panel is fastened, the washer compresses into a gasket between the screw head and the steel. Hot summers and cold winters cycle that rubber until it hardens, cracks, and loses its grip. At the same time, thermal movement slowly backs the screw out, releasing washer pressure. Water then wicks down the shank.
Installation errors compound it. An overdriven screw crushes the washer and dimples the panel into a small funnel. An underdriven screw never seats the washer. A screw driven at an angle leaves a gap on one side. A screw that missed the framing member behind the panel holds nothing and spins in an oversize hole.
Because a hardened washer and a healthy washer look nearly identical from the ground, a single leaking screw is hard to isolate visually. Practitioners often re-treat a whole row or a whole slope rather than gamble on the one screw they think is guilty.
How do you find a metal roof leak?
Find a metal roof leak by working from the inside out: trace the water stain in the attic to a high point, then inspect the exterior directly above and uphill of it. Water travels down a rafter or purlin before it drips, so the entry point almost always sits higher on the slope than the stain suggests. Confirm with a controlled hose test on a dry day.
- Attic first. On a bright day, look for daylight through screw holes, and for rust trails, wet insulation, or staining on the underside of the deck or purlins. Mark the highest wet point.
- Exterior above the mark. Inspect the panels uphill of the interior stain. Look for screws that stand proud of the panel, screws with cracked or missing washers, open seams, and cracked flashing sealant.
- Hose test. Starting low and moving uphill, run water over one zone at a time while a second person watches the attic. Isolating zones tells you the exact course that leaks, instead of soaking the whole roof at once.
Two spots deserve extra attention because they cause a large share of penetration leaks across all roof types: the pipe boot and the flashing. See our roof vent pipe boot guide and roof flashing repair guide for those diagnoses in detail.
How do you fix a metal roof leak around screws?
Fix a leaking metal roof screw by removing the old fastener and driving a larger-diameter replacement with a fresh EPDM washer, not by tightening the original. Retightening a backed-out screw usually crushes an already hardened washer and strips the hole. The correct repair goes up one screw size so the new threads bite fresh metal, and pairs that screw with a UV-stable EPDM washer rather than an old neoprene one.
- Back the old screw out. Note whether the hole is enlarged or the framing was missed. A spinning screw means it missed structure.
- Choose an oversize replacement. Step up one diameter, typically from a #9 or #10 to the next size, or from #12 to #14, so the new threads grab metal the old ones stripped.
- Use an EPDM-washered screw. EPDM outlasts neoprene under UV. Standard exposed-fastener metal screws use a bonded washer rated for roofing service.
- Drive it straight and seat, do not crush. Stop when the washer bulges slightly past the metal cap. Overdriving splits the washer; underdriving never seals.
- Cap with sealant. Add a small dome of metal-grade polyurethane or a self-leveling roof sealant over the head, extending about half an inch onto the panel, to encapsulate the joint.
If the hole is badly enlarged or the screw missed framing, do not simply keep upsizing. Move to a nearby screw that hits structure, then fill the abandoned hole with sealant or a stitch screw and butyl. When a whole slope shows hardened washers, budget a full re-screw rather than repeated one-off fixes.
How do you seal a metal roof leak at a seam?
Seal a leaking metal roof seam by removing the old, brittle sealant back to bright metal, then rebonding the lap with butyl tape or a metal-grade polyurethane, depending on the panel type. On through-fastened panels the side and end laps are sealed with butyl tape and stitch screws. On a standing seam roof, a separated seam usually needs re-crimping or a manufacturer mastic, not a bead of caulk over the top.
- Clean the lap. Wire-brush rust and scrape old sealant off both mating surfaces. Wipe with solvent so the new sealant bonds to clean metal, not to residue.
- Re-bond the lap. Lay fresh butyl tape inside the lap where possible, then draw the panels together with stitch screws every few inches so the butyl compresses.
- Top-seal if exposed. Over an exposed end lap, run a bead of UV-stable polyurethane along the uphill edge. Avoid leaving butyl exposed to sun, since butyl is not UV resistant.
A standing seam that has pulled apart is a different job. The seam is a mechanical fold, and the durable fix is re-seaming with the correct crimping tool or applying the manufacturer’s approved seam sealant. A surface smear of household silicone over a standing seam is a short-lived patch.
Which sealant should you use on a metal roof?
Use a metal-grade polyurethane for exposed screw heads and flashing, butyl tape inside seams and laps, and reserve silicone for surfaces where paintability does not matter. The wrong choice is the reason many DIY metal roof repairs fail within a season: standard household silicone often will not bond durably to coated steel and cannot be painted to match. Match the material to the failure location.
| Sealant | Best use on a metal roof | Strength | Watch-out |
|---|---|---|---|
| Butyl tape | Inside side/end laps and under flashing | Stays flexible, compresses into a gasket | Not UV resistant; must stay concealed |
| Polyurethane (metal-grade) | Screw heads, exposed laps, flashing beads | High UV resistance, paintable, weatherproof | Longer cure; surface must be clean |
| Silicone (neutral-cure) | General exposed gaps where color match is not needed | UV safe and flexible | Not paintable; poor adhesion to some coatings |
| Self-leveling roof sealant | Doming over fastener heads on low slopes | Flows to encapsulate the head | For low-slope areas; can run on steep pitch |
For a broader look at trowel-grade patching compounds and where they fit, see our guide to roofing cement types and application.
How do you patch a hole in a metal roof?
Patch a metal roof hole by covering it with a same-metal patch that overlaps the damage by at least two inches on every side, bedded in sealant and fastened or bonded to the panel. A dab of caulk alone spans only tiny punctures. For anything larger than a nail hole, cut a patch from matching metal (matching galvanic type to avoid corrosion between dissimilar metals) so it moves with the roof and does not set up a rust cell.
- Clean and de-rust. Wire-brush to bright metal and remove coating residue around the hole.
- Cut a patch. Size it two inches beyond the damage all around, with rounded corners so it will not lift.
- Bed and bond. Butter the underside with metal-grade sealant, press it down, and either bond or fasten the edges, then seal the perimeter.
Small rust perforations get the same treatment after you address the corrosion: brush it back, prime the bare steel, then patch. Widespread rust is usually a re-coat or re-roof decision rather than a patch, which our metal roof maintenance guide covers alongside inspection intervals.
How often should metal roof screws be replaced?
Plan to inspect exposed metal roof screws every 2 to 3 years and expect targeted or full screw replacement somewhere around 7 to 15 years, sooner in harsh climates or after repeated wind events. Screws and their washers do not fail on a fixed schedule; they fail with UV exposure, thermal cycling, and installation quality. A roof in a hot, high-UV, or storm-prone area reaches replacement sooner than one in a mild climate.
When you do replace, go up one screw diameter across the affected area so the new threads seat in fresh metal, and switch to EPDM-washered fasteners. Re-screwing an entire slope at once is often cheaper per screw and more reliable than returning for one leaking fastener after another. Twice-yearly visual checks, plus a look after major storms, catch backed-out screws before they stain a ceiling.
How much does metal roof leak repair cost?
Metal roof leak repair typically runs from about $15 to $75 in materials for a handful of do-it-yourself screw replacements, up to roughly $400 to $1,000 for a professional leak repair, and more when the leak is extensive. Simple fastener and sealant work sits at the low end. Seam re-sealing, flashing replacement, or a re-screw across a slope moves the price up. Cost tracks the source and the access, not the size of the drip.
| Repair | Typical cost range | Notes |
|---|---|---|
| DIY screw + washer + sealant | $15 to $75 (materials) | A few fasteners and a tube of sealant |
| Pro screw replacement (targeted) | $150 to $1,000 | Depends on count, access, and pitch |
| Professional leak repair (general) | $400 to $1,000 | Doubles or more for major or multi-source leaks |
| Restorative roof coating | $3 to $7 per sq ft | Whole-roof option when leaks are widespread |
| Full replacement | $15 to $20 per sq ft | End-of-life or extensive corrosion |
Costs vary by region, roof pitch, panel type, and how many sources are leaking. A single backed-out screw is a cheap afternoon; a slope of hardened washers or a failing standing seam is a different budget. For whole-roof pricing context, see our metal roof cost guide.
When should you call a professional?
Call a professional when the leak is on a standing seam roof, when it involves widespread rust or multiple sources, or when it sits on a steep or high roof you cannot access safely. DIY screw and sealant work suits a reachable exposed-fastener panel with an isolated leak. Beyond that, the failure modes need tools and judgment a homeowner usually lacks, and a botched repair can spread water damage before it is caught.
Two cautions apply regardless of who does the work. First, a DIY repair may void a manufacturer or workmanship warranty in many cases, so check your coverage before you touch the roof. Second, sealant is a repair, not a cure: if screws are backing out roof-wide or the coating is failing, sealing individual points only buys time until a re-screw, re-coat, or replacement.
Reviewed by The Roofing Brief Team. Last reviewed July 2026.