Chimney flashing for a metal roof works differently than it does on shingles because the flashing cannot be nailed through the panels and then forgotten. A metal roof moves as it heats and cools, and the flashing has to move with it, seal against a rib or a standing seam instead of a flat field, and pair with a compatible metal so the two do not corrode where they touch. Get those three things right (movement, attachment, and metal pairing) and the joint stays dry for the life of the roof.
This guide covers the four flashing parts, how attachment changes by panel profile, the thermal-movement rule that ruins most site-built jobs, a metal-compatibility chart to avoid galvanic corrosion, when a cricket is required, and what the work costs in 2026.
How is chimney flashing on a metal roof different from a shingle roof?
On a shingle roof, step flashing tucks under each course and gets nailed to the deck. On a metal roof there are no courses to weave into and you cannot fasten flashing through the field of a panel without creating a leak and locking the panel in place. Instead, flashing seals to the panel profile (a standing seam, an exposed-fastener rib, or a corrugation) with butyl tape, closures, and a counter flashing that floats over the base so the panel can expand and contract underneath.
The result is that metal-roof chimney flashing is usually custom formed or ordered as a pre-made curb, costs more than a shingle equivalent, and lives or dies on details that have nothing to do with a shingle install: sealant chemistry, panel attachment, and dissimilar-metal contact.
The four parts of a chimney flashing system
Every chimney flashing job, metal roof or not, is built from four parts installed in a set order so water always laps onto a lower piece, never behind it. On a metal roof each part is formed from coil stock matched to the roof or ordered as a manufacturer curb kit.
| Part | Location | Job | Metal-roof note |
|---|---|---|---|
| Apron (base) flashing | Downslope face of chimney | Sheds water onto the panels below | Sits on top of the panel, sealed with butyl tape at the rib |
| Step or side flashing | Both sides, running up the slope | Carries water down past the sidewalls | Formed as a continuous pan or soldered/lapped pieces, not woven shingle-style |
| Back pan or cricket | Upslope side | Splits water around the chimney | A back pan for narrow chimneys, a peaked cricket for wide ones |
| Counter (cap) flashing | Set into the masonry | Covers the top edge of the base flashing | Floats over the base so the panel can move; embedded in a cut reglet, not surface-caulked |
The counter flashing is the part most DIY jobs get wrong. It should be let into a saw-cut reglet in the mortar joint and folded down over the base flashing, hanging free. A bead of caulk smeared onto the brick face is a two-year fix, not a twenty-year one.
How does flashing attach by metal panel type?
Attachment is the biggest split in metal-roof chimney work, and it depends entirely on the panel profile. Standing seam hides its fasteners and must not be penetrated in the field, so flashing clamps or seals to the raised seam. Exposed-fastener and corrugated panels seal at their ribs with tape and closures. Matching the method to the panel is the difference between a dry joint and a chronic leak.
| Panel type | How flashing attaches | Sealing detail |
|---|---|---|
| Standing seam | Clamps or a curb that ties to the seams, no field penetrations | Butyl tape and a floating counter flashing; often a factory curb (for example a Sheffield Metals or Western States curb) |
| Exposed fastener (R-panel, PBR) | Trim laps over the panel and fastens at the ribs with gasketed screws | Butyl tape under the trim plus inside/outside closure strips at the ribs |
| Corrugated | Trim shaped to the wave, fastened at the crowns | Foam or profiled closure strips seal the gaps under the flashing |
For a round metal chimney or Class A pipe instead of a masonry stack, the base flashing is replaced by a pipe boot sized to the pipe diameter (an EPDM or silicone boot such as Dektite or Master Flash), with a storm collar above it. On a ribbed panel the boot needs a flat mounting area or a matching profiled base to seal.
Why metal roof flashing has to float with thermal movement
A metal roof expands when it heats and contracts when it cools, and a long run can move on the order of an inch per 100 linear feet across a wide temperature swing. Aluminum moves roughly twice as much as steel for the same temperature change. If flashing is fastened tight to both the chimney and the panel, that movement tears the sealant, elongates the screw holes, and opens the joint.
The fix is to let the roof move independently of the chimney. Fasten the base flashing to the roof side only, keep the counter flashing hanging free over it, and never screw step or side flashing through the panel into the deck in a way that pins the panel. On standing seam this is why clamp-on curbs and clip systems exist: they hold the flashing while the panel slides underneath.
Which flashing metal is compatible with which roof (galvanic corrosion)
Galvanic corrosion happens when two dissimilar metals touch with water present, and the less noble metal eats away. On a chimney joint, rainwater is the electrolyte and the wrong flashing metal against your panel can rot through in a few seasons. The safe rule is to match the flashing metal to the panel, or isolate them with a barrier so they never touch.
| Roof panel | Compatible flashing | Avoid |
|---|---|---|
| Galvalume (AZ50/AZ55 coated steel) | Galvalume, coated (Kynar/PVDF) steel | Copper, bare lead, raw aluminum in direct contact |
| Galvanized steel | Galvanized, coated steel | Copper and lead (they corrode the zinc coating) |
| Aluminum | Aluminum, coated steel with a barrier | Copper (severe), bare steel |
| Copper | Copper, lead-coated copper, stainless | Aluminum, galvanized, Galvalume downstream of it |
Copper is the worst offender because runoff carries copper ions downslope, so even a copper flashing, gutter, or pipe above a Galvalume or aluminum panel can corrode metal it never physically touches. Where mixing is unavoidable, separate the metals with an underlayment membrane, butyl tape, or a coated barrier so they are not in direct contact and are not stacked upstream to downstream.
When does a metal roof chimney need a cricket?
A cricket is a small peaked saddle behind the chimney that splits water and debris around it instead of letting it pond against the upslope face. Many code editions and manufacturer details call for a cricket when the chimney is wider than 30 inches measured across the slope, and a lot of metal roofers add one at 18 inches or on any chimney low on a long slope where water volume is high.
On a metal roof the cricket is formed from the same panel or coil stock, tied into the back pan, and sized so its own slope sheds water well. Skipping it on a wide chimney is one of the most common causes of a leak that shows up years later as rot in the upslope corner. For sizing and build sequence, see the dedicated chimney cricket install guide.
Factory curb kits vs site-formed flashing
You can either bend flashing on site from matching coil stock or order a pre-manufactured curb or boot sized to the chimney and panel. Factory curbs from metal-roof makers arrive with the right profile, butyl already channeled, and a finish that matches the panel, which lowers the odds of a leak on a standing seam roof. Site-formed flashing is cheaper and fine for a skilled sheet-metal crew, but it depends entirely on the installer.
- Factory curb or boot: best for standing seam and round penetrations, matched finish, higher part cost, fewer field errors.
- Site-formed coil flashing: lower material cost, works on any profile, quality rides entirely on the crew’s sheet-metal skill.
- EPDM/silicone pipe boot: for round pipe only, sized by pipe diameter, pair with a storm collar and expect to inspect the rubber every few years.
What does it cost to flash a chimney on a metal roof in 2026?
Flashing a chimney on a metal roof typically runs about $400 to $1,600 installed for a standard masonry chimney, and more when a wide cricket, a standing seam curb system, or panel rework is involved. Metal-roof flashing costs more than a shingle equivalent because the parts are custom formed or ordered as a curb kit rather than pulled off a shelf.
| Line item | Typical 2026 range | Notes |
|---|---|---|
| Flashing material | ~$0.50/ft (galvanized) to $2-$3/ft (copper) | Coil stock, before fabrication |
| EPDM/silicone pipe boot | $15-$60 part | Round pipe penetrations |
| Standing seam factory curb | $150-$600+ part | Matched profile and finish |
| Full flashing install (labor + parts) | $400-$1,600 | Standard masonry chimney |
| Cricket added | +$300-$2,000 | Scales with chimney width and pitch |
Prices vary by region, pitch, chimney size, and metal choice, so treat these as planning ranges and get an itemized quote. Copper flashing sits at the top of the range and can double material cost on its own.
Installing metal roof chimney flashing: the order that matters
The install order is what makes flashing waterproof, because every piece has to lap onto the one below so water runs over a joint, never into it. This is the sequence a metal-roof crew follows on a masonry chimney.
- Set the base: lay the apron flashing across the downslope face, on top of the panel, bedded in butyl tape at the rib.
- Run the sides: form and lap the side flashing up both walls, sealing to the panel profile with tape and closures, fastened to the roof side only.
- Build the back: install a back pan for a narrow chimney or a cricket for a wide one, tied into the side flashing.
- Cut the reglet: saw a groove into the mortar joint around the chimney for the counter flashing.
- Set counter flashing: fold the top edge into the reglet, seal the reglet, and let the flashing hang free over the base so the panel can move.
- Seal and inspect: tool sealant only where the detail calls for it, then check every lap for correct overlap direction.
If the existing flashing is failing rather than new, diagnose the failure mode first. The metal roof leak repair guide walks through finding and sealing a leak by source, and bad chimney flashing covers the warning signs before it leaks inside.
Common metal roof chimney flashing mistakes
Most flashing leaks trace back to a short list of avoidable errors, and on a metal roof they cluster around movement, penetration, and metal pairing. Watch for these.
- Pinning the panel: fastening flashing through the panel field so thermal movement tears the joint.
- Surface-caulked counter flashing: caulk on the brick face instead of a cut reglet, which fails in a few years.
- Dissimilar metals touching: copper or bare aluminum against Galvalume or galvanized, driving galvanic corrosion.
- Reverse laps: an upper piece tucked behind a lower one, funneling water under the flashing.
- Relying on sealant alone: sealant is a backup to correct laps and closures, not the primary seal.
- Skipping a cricket: no saddle on a wide chimney, so water and debris pile against the upslope wall.
For how these parts fit into the whole roof, the metal roof components guide names every accessory, and Galvalume metal roofing explains the coating that decides which flashing metals are safe against your panel.
Frequently asked questions
Can you put chimney flashing on a metal roof yourself?
A skilled DIYer can flash a round pipe with a sized EPDM or silicone boot and storm collar. Flashing a masonry chimney on a metal roof is harder because it needs custom-formed pieces, a cut reglet, correct laps, and matched metals. On a standing seam roof most owners are better off with a factory curb kit or a metal-roof crew, since a field mistake often means pulling panels to fix.
What is the best flashing material for a metal roof chimney?
Match the flashing to the panel. A Galvalume or galvanized roof takes Galvalume or coated (Kynar/PVDF) steel flashing. An aluminum roof takes aluminum flashing. A copper roof takes copper or stainless. Avoid pairing copper or bare aluminum with a coated-steel panel, because galvanic corrosion will eat the less noble metal where they touch or downstream of copper runoff.
Does a metal roof chimney need a cricket?
A cricket is commonly required when the chimney is wider than 30 inches measured across the slope, and many metal roofers add one at 18 inches or on any chimney sitting low on a long slope. The cricket splits water and debris around the upslope face. Skipping it on a wide chimney is a frequent cause of a leak that shows up later as rot in the upslope corner.
Why does chimney flashing leak on a metal roof?
The usual causes are thermal movement tearing a joint that was fastened too tight, a counter flashing caulked to the brick instead of set in a reglet, dissimilar metals corroding where they touch, reverse laps that funnel water under the flashing, or a missing cricket on a wide chimney. Diagnose the failure mode before resealing, since caulk over a bad detail buys only a season or two.
How much does it cost to flash a chimney on a metal roof?
Expect roughly $400 to $1,600 installed for a standard masonry chimney, with more added for a wide cricket, a standing seam curb system, or panel rework. Copper flashing sits at the top of the range. A round pipe with an EPDM or silicone boot is cheaper, often a part cost of $15 to $60 plus labor. Prices vary by region, pitch, and chimney size.
Can you flash a chimney on a standing seam roof without penetrating the panels?
Yes, and you should. Standing seam panels are meant to move and hide their fasteners, so flashing clamps or ties to the raised seams and uses a curb that lets the panel slide underneath. Butyl tape and a floating counter flashing seal the joint. Screwing flashing through the field of a standing seam panel pins it, tears at the fastener as the panel moves, and causes leaks.
Reviewed by The Roofing Brief Team. Last reviewed July 2026.