Skip to content
ARMORTHANE PROTECTING YOUR WORLD

PROTECTING YOUR WORLD

ARMORTHANE PROTECTING YOUR WORLD

Metal Roof
Leak Repair:
Screws, Laps & Flashings

Where metal roofs really leak, how to repair each source properly, what it costs in 2026, and when a full restoration beats chasing screws.
Metal Roof Quotes

Metal roof leaking? Seal it for good.

Tell us the building type, roof size, panel type and where it leaks. We will connect you with a certified applicator near you.

  • Roof size and panel type
  • Where and when it leaks
  • Rust and fastener condition
  • Insulation needs
Rather talk now? Call (417) 831-5090
Step 1 of 3
0.78 in
Growth of a 100 ft steel panel through a 100°F temperature swing; aluminum moves twice as much
Metal Sales
~80
Exposed screws per 100 sq ft on a typical through-fastened metal roof, each one a potential leak
Fence & Deck Supply
$300–$1,500
Typical metal roof repair cost, with a national average around $900
HomeGuide, 2026
3:12
Minimum slope for lapped metal panels without lap sealant; standing seam can go to 1/4:12
IRC R905.10.2

Metal roof leak repair is mostly a fastener and lap problem. A through-fastened steel roof has thousands of screws, every one sealed by a small rubber washer, and every panel grows and shrinks with the sun. Over the years that movement works the screw holes oval, washers dry out, and the roof starts leaking in a dozen places at once. We manufacture the polyurea, polyurethane and spray foam systems our certified applicators use to seal and restore metal roofs on barns, shops, warehouses and homes. This guide covers where metal roofs actually leak, how to repair each source properly, what it costs, when a full restoration makes more sense than chasing screws, and two calculators: one for thermal movement and one for repair versus restoration cost.

Quick answer

Find the leak source first: on exposed-fastener roofs it is usually failed screw washers, backed-out or overdriven screws, open side and end laps, or flashing at ridges, walls and penetrations. Replace failed screws (one size larger where the hole is stripped), seal laps with a compatible butyl or urethane sealant, and rebuild flashings rather than caulking over them. If failures are spread across the whole roof, or rust is starting at laps and fasteners, a restoration system that encapsulates fasteners, reinforces seams and coats the entire roof is usually cheaper over time than repeated spot repairs.

What's in this guide
  1. 1Where metal roofs leak
  2. 2Thermal movement calculator
  3. 3Metal roof leak repair by source
  4. 4Repair costs compared
  5. 5Repair vs. restore estimator
  6. 6When to restore instead
  7. 7How our applicators do it
  8. 8FAQ
Diagnosis

Where metal roofs actually leak

A metal panel itself almost never leaks until it rusts through. Water gets in at the joints and holes: screws, laps, trim and penetrations. Here is what we find when we walk a leaking metal roof, roughly in order of how often:

Most common

Screw washers and fasteners

Washers crack and harden in UV. Screws driven too tight crush the washer flat; too loose leave a gap; driven at an angle, the washer never seats. Thermal movement puts repeated load on every screw and slowly enlarges the holes, so screws back out.

Common

Side and end laps

Where panels overlap, wind-driven rain and capillary action pull water uphill into the lap. Lap sealant tape dries out, and low-slope roofs hold water against laps longer than they were designed for.

Common

Flashings and trim

Ridge caps with missing closures, sidewall and headwall flashings that were face-sealed with caulk, eave trim that lets water back under, and valleys that were never hemmed.

Common

Penetrations

Pipe boots that have split, skylights, exhaust fans and HVAC curbs cut into ribs. Penetrations through the rib or across the panel flat are harder to seal than they look.

Older roofs

Rust-through

Rust starts at cut edges, laps, fastener holes and anywhere water sits. Copper or treated lumber in contact with galvanized steel accelerates it. Once rust perforates the panel, that section needs replacing.

Not a leak

Condensation

Drips on cold mornings with no rain are usually condensation on the underside of the panels, not a roof leak. No amount of screw replacement fixes that. Our metal roof condensation guide covers the fix.

Check the slopeThe model code minimums for metal panels are 3:12 for lapped, non-soldered panels without lap sealant, 1/2:12 with applied lap sealant, and 1/4:12 for standing seam. A lapped roof below its minimum slope will leak at the laps no matter how many times they are caulked.
Tool 1

Why the screws keep leaking: thermal movement

Every metal roof moves. A dark steel roof can go from a cold, clear night to a hot afternoon in a few hours, and the panel grows and shrinks each time. On a through-fastened roof, the screws are what resists that movement, which is why fastener holes slowly elongate and leaks come back. Standing seam roofs use sliding clips so panels can move; through-fastened panels cannot. Enter your panel run to see how much movement your fasteners are fighting.

Thermal movement calculator

How far do my panels move?

Movement = coefficient x panel length x temperature swing. Steel 0.0000065 and aluminum 0.0000128 per °F (Metal Sales). Field movement can be up to 20% less than theory because of friction (Construction Canada).

Used when Custom is selected
—
Theoretical movement
—
Likely field movement
—
Each end, if pinned at mid-run

Repairs

Metal roof leak repair by source

Leaking screws

Do not just tighten old screws. A hardened washer will not reseal, and overtightening crushes it. Back the screw out, look at the hole and the washer, and replace it. If the hole is stripped or oval, use a larger-diameter replacement screw made for that purpose. Drive it straight, and stop when the washer is snug and just starting to bulge, not squashed flat. EPDM washers hold up better in direct sun than neoprene. If a screw missed the purlin entirely, pull it and seal the hole with a properly fastened patch or a stitch screw and sealant, not caulk alone.

Open laps

Clean the lap, remove old failed sealant, and reseal with a compatible butyl tape or urethane sealant, then add stitch screws at the spacing the panel manufacturer specifies to pull the lap tight. On low-slope roofs with recurring lap leaks, reinforced seam treatment (fabric embedded in a base coat) is more durable than sealant alone.

Flashings and trim

Caulk is maintenance, not flashing. Sidewall and headwall flashings need to shed water by lapping, with counterflashing or a reglet into the wall. Replace missing ridge and eave closures, re-hem valleys, and make sure trim laps run with the water, not against it.

Penetrations and rust

Replace split pipe boots with ones sized for the pipe and the panel profile. For curbs, install a proper cricket or diverter on the uphill side. Treat surface rust by removing loose scale, priming bare steel with a rust-inhibiting primer, and coating. Panels rusted through get replaced or patched with matching metal, fastened and sealed, not covered with roof cement.

SafetyMetal roofs are slippery when wet, dewy or dusty, and screw-fastened panels can buckle between purlins. Use fall protection, walk on the purlin lines, and keep off the roof in wind or rain.
Costs

What metal roof leak repair costs

Typical 2026 installed price ranges. Click a heading to sort.

RepairTypical costUnitBest for
Screw and fastener replacement$150–$1,000per jobLeaks at a limited number of screws
General leak repair$200–$1,000per leakOne identified source
Seam resealing$250–$1,100per jobOpen side or end laps
Rust repair$300–$3,000per jobLocalized rust at laps or fasteners
Coating, metal roof$0.50–$4.00per sq ftWeathered roof, many small leaks
Silicone restoration system$2.50–$5.00per sq ftCommercial roofs: fasteners, seams and rust treated
Spray foam plus silicone$4.00–$8.00per sq ftRoof also needs insulation or slope
Panel replacement$3–$14per sq ftRusted-through or storm-damaged panels
Sources: HomeGuide metal roof repair and roof coating cost guides (2026); West Roofing Systems commercial metal roof restoration costs.
Tool 2

Repair vs. restore: metal roof estimator

Count a few panels' worth of screws during your inspection and note how many have cracked, missing or crushed washers, or are backing out. That failure rate tells you whether you are looking at a repair or a restoration. The estimator scales it to the whole roof.

Repair vs. restore

Patch it or restore it?

Fasteners = area x 0.8 per sq ft. Restoration = $2.50–$5.00 per sq ft; each inch of spray foam adds $1.00–$1.50 per sq ft and about R-6.5 (West Roofing). Panel replacement $3–$14 per sq ft (HomeGuide).

Add spray foam under the coating?
—
Exposed fasteners on the roof
—
Fasteners likely failing now
—
Restoration estimate

Restoration

When to restore instead of chasing leaks

If the panels are structurally sound but the screws, laps and paint are all aging at the same rate, fixing one leak just moves you on to the next. A restoration treats the whole roof at once: wash and degrease, remove loose rust, prime bare steel, replace or encapsulate fasteners, reinforce every lap and flashing joint, then apply a continuous coating across the whole surface. The Roof Coatings Manufacturers Association says a properly applied coating can extend roof life up to 10 years or more, and the coating can be renewed later.

Our applicators restore metal roofs with spray-applied polyurea and polyurethane systems over ArmorPrime primers, and with ArmorFoam Roof 200 spray foam topped with UV TopCoat where the building also needs insulation. Foam has a second benefit on low-slope metal: it can be built up to improve drainage at problem laps. See metal roof waterproofing, our metal coating guide and corrosion prevention for system details.

When restoration is the wrong call

  • Panels are rusted through over large areas. Coatings do not add structural strength. Replace the bad panels first, or re-roof.
  • The roof is below minimum slope for its panel type. A coating can bridge laps, but standing water will find any weak spot. Fix the slope (foam can help) or plan for it.
  • Standing seam with floating clips. These roofs must be free to move. Seams can be treated with a flexible system, but rigidly bonding panels together defeats the clips. Use a system rated for that roof.
  • It is really condensation. Coating the outside does nothing for moisture forming underneath.
Leaking metal roof?

Seal every screw and seam in one visit.

A certified ArmorThane applicator can inspect your metal roof, fix the active leaks and quote a seamless polyurea or foam restoration if the roof is a good candidate.

Get a free quoteFind an applicator

Contractors: become an applicator →

Process

How our applicators repair a leaking metal roof

  1. Trace the leaks

    Match interior stains and drips to the roof above, then water-test suspect laps, screws and flashings one section at a time. Rule out condensation.

  2. Assess fasteners and rust

    Sample screws across the roof, check for backed-out and overdriven fasteners, and map rust at laps, eaves and penetrations.

  3. Clean and prep

    Pressure wash, degrease, remove loose rust and scale, and prime bare metal so the coating has something sound to bond to. On larger jobs, adhesion is checked on the actual roof; ASTM D4541 is the pull-off method for coatings on metal.

  4. Fix the details

    Replace failed fasteners, stitch and seal open laps, rebuild flashings, and reinforce seams and penetrations.

  5. Coat or foam the field

    Apply the coating or foam system to the specified thickness, check it, and give the owner the inspection record and maintenance schedule.

Leaks on a flat or membrane roof? See our commercial roof leak repair guide.

FAQ

Metal roof leak repair questions

What is the most common cause of a leaking metal roof?

Failed fasteners. Washers harden and crack, screws are overdriven or underdriven at installation, and thermal movement gradually enlarges the screw holes so screws back out. Open side and end laps and failed flashings are the next most common sources.

Can I just tighten the screws on my metal roof?

Rarely. An old washer that has hardened will not reseal when tightened, and overtightening crushes it so it leaks faster. Remove the screw, check the hole and replace the screw, using a larger-diameter replacement screw if the hole is stripped.

How much does it cost to fix a leaking metal roof?

2026 cost guides put typical metal roof repairs at $300 to $1,500, with fastener replacement jobs at $150 to $1,000 and seam resealing at $250 to $1,100. Commercial silicone restoration systems run about $2.50 to $5.00 per square foot, and panel replacement $3 to $14 per square foot.

Should I use caulk to fix a metal roof leak?

Sealant is part of a lap or flashing repair, but caulk smeared over a leaking screw or face-sealed onto a wall flashing is a short-term patch. Fix the underlying fastener, lap or flashing detail and use sealants compatible with the panel finish.

Why does my metal roof drip when it is not raining?

That is almost always condensation. Warm, moist air inside the building hits the cold underside of the panels and condenses, usually on cold, clear nights. It needs insulation, an air and vapor control layer, and moisture control, not roof repairs.

Can you coat over a leaking metal roof?

Yes, after the leaks are repaired and the roof is prepared. A restoration system includes cleaning, rust treatment, priming, fastener and seam treatment, and then the coating. Coating over active leaks, wet insulation or rusted-through panels without repairs just hides the problem.

How long does a metal roof coating last?

It depends on the chemistry, the thickness applied and the climate. The Roof Coatings Manufacturers Association says a properly applied roof coating can extend roof life up to 10 years or more, and most systems can be recoated when they wear.

Is a standing seam roof repaired differently?

Yes. Standing seam panels float on clips to allow thermal movement, so leaks are usually at seams, end laps, penetrations and trim rather than exposed screws. Repairs and coatings must not lock the panels together; use seam treatments and systems approved for floating standing seam roofs.

AT
Written by the ArmorThane technical team. We have manufactured polyurea, polyurethane and spray foam systems since 1989 and support certified applicators who repair and restore metal roofs. Cost figures are third-party 2026 ranges, not ArmorThane pricing. Updated October 2026.

Sources

  1. Metal Sales, Thermal Expansion and Contraction with Metal Panels: metalsales.us.com/blog/thermal-expansion
  2. Construction Canada, Controlling Thermal Movement in Metal Panel Roofs: constructioncanada.net/controlling-thermal-movement-in-metal-panel-roofs
  3. FRSA, Fastener Failure in a Metal Roofing World: floridaroof.com/Fastener-Failure-in-a-Metal-Roofing-World
  4. Mid Florida Metal Roofing Supply, EPDM vs Neoprene Screw Washers: midfloridametalroofingsupply.com/epdm-vs-neoprene-screw-washers
  5. Fence & Deck Supply, Metal Roofing Screw Calculator: fencedecksupply.com/blog/metal-roofing-screw-calculator
  6. HomeGuide, Metal Roof Repair Cost (2026): homeguide.com/costs/metal-roof-repair-cost
  7. HomeGuide, Roof Coating and Sealing Cost (2026): homeguide.com/costs/roof-coating-or-sealing-cost
  8. West Roofing Systems, Cost to Restore a Commercial Metal Roof: westroofingsystems.com/ballpark-cost-restore-commercial-metal-roof
  9. Building Code Trainer, Minimum Roof Slopes by Roofing Material (IRC R905.10.2): buildingcodetrainer.com/minimum-roof-slopes-required-by-roofing-material
  10. ASTM D4541, Pull-Off Strength of Coatings Using Portable Adhesion Testers: store.astm.org/d4541-22
  11. Roof Coatings Manufacturers Association, FAQs: roofcoatings.org/faqs

latest news & bLOGS

Learn more

Every screw sealed, every seam reinforced.

Owners get a certified ArmorThane applicator who fixes the active leaks and can restore the whole metal roof with a seamless system. Contractors can add metal roof restoration with no franchise fee and no royalties.

Find an applicator →Become an applicator
United States 417-831-5090 · Canada 780-444-6200

CONTACT US

REQUEST A QUOTE OR

BECOME AN APPLICATOR

ArmorThane has built a strong reputation over the past 30 years for producing high-quality, durable protective coatings.

group 115 660555abebfe4
Phone Number

Tel: 417.831.5090

group 115 1 660556c21395c
Email Us

moreinfo@armorthane.com

Step 1 of 3

We want to help you find the best ArmorThane applicator for your protective coating project. Please either fill out the request form below or call us toll free at 417-831-5090, any time Monday-Friday, 8:00 a.m. to 5:00 p.m. Central Standard Time.

RV Find An Applicator

Step 1 of 3

Connect with an authorized ArmorThane professional to get a long-lasting, seamless protective coating for your RV. Submit the form below or call us directly at 417-831-5090 (Monday–Friday, 8:00 AM – 5:00 PM CST).

Facebook Twitter Youtube

Find An Applicator

Applicator Login

Armorthane Logo Outlined
CALL NOW
BECOME APPLICATOR
FIND APPLICATOR

Protective Coating Applications

Products

Applicator Opportunities

Knowledge Center

Galleries