Cost to Replace Roof Flashing

The cost to replace roof flashing is $200 to $1,500 at a single location such as a chimney, a wall, a valley, or a skylight. A whole-roof reflash during a shingle replacement is $1,500 to $4,000.

Flashing is the metal that seals the joints where the roof plane meets something else. It is the single most common source of roof leaks, and it wears out faster than the shingles around it.

What It Costs to Replace Roof Flashing

A pipe-boot swap is $150 to $400. Wall or valley flashing is $250 to $1,000. Chimney flashing is the priciest at $300 to $1,500, because it needs two layers of metal woven together.

A whole-roof reflash, done as part of a shingle replacement, is $1,500 to $4,000 and is standard scope on any proper reroof.

The table below shows cost by location. Labor is most of the bill; the metal itself is cheap.

What Flashing Is and Why It Fails

Flashing is thin metal, usually aluminum, galvanized steel, or copper, bent to bridge a joint and shed water back onto the shingles. Step flashing runs up a wall, counter flashing caps it, valley flashing lines a valley, and a boot seals a pipe.

It fails from corrosion, from sealant drying out and cracking, from movement between the roof and a chimney or wall, and from a previous roofer using caulk instead of proper metal.

Because flashing sits at the lowest, wettest points of the roof, a small failure leaks quickly. See our cost to repair a roof leak guide for the leak side.

Cost by Flashing Location

Chimney flashing is $300 to $1,500. It needs step flashing woven into the shingles and counter flashing let into the mortar joints, so it is the most labor.

Wall or headwall flashing where a roof meets a vertical wall is $250 to $900. Valley flashing is $300 to $1,000 depending on length and whether shingles have to be cut back.

A plumbing-vent pipe boot is $150 to $400. Skylight flashing is $300 to $1,000, often sold as a kit matched to the skylight. Drip edge along an eave or rake is $2 to $5 per foot.

Where the Money Goes

Labor is most of a flashing job. The roofer has to lift and often replace the surrounding shingles, remove the old metal, fit and fasten the new metal, and reseal, all by hand.

Materials are cheap by comparison: a few feet of flashing stock, fasteners, underlayment, sealant, and a bundle of matching shingles.

Masonry work on a chimney, like grinding out and repointing the mortar joints for the counter flashing, can add $200 to $800. See our Roofing cost guides for related jobs.

What Drives the Price Up

A steep or high roof adds staging and safety time. A chimney that also needs a new crown, repointing, or a cricket behind it turns a flashing job into a chimney job.

Matching old, weathered shingles is often impossible, so a flashing repair can mean a visible patch or a larger shingle area replaced to blend it.

If the leak already rotted the decking or sheathing at the joint, that repair is added at $70 to $120 per sheet.

Repair, Reseal, or Replace?

If the metal is sound and only the sealant has failed, a roofer can clean and re-caulk the counter flashing for $150 to $400. It is a stopgap that buys a few years.

If the metal is corroded, bent, or was never installed correctly, replace it. Caulk over bad flashing always fails again.

If the roof itself is near end of life, fold the flashing into a full roof replacement, where new flashing is standard and cheaper as part of the whole job.

Flashing and a New Roof

A proper roof replacement includes new valley metal, new step and counter flashing at walls and chimneys, new pipe boots, and new drip edge. Reusing old flashing is a red flag on a roofing quote.

The exception is sometimes a masonry chimney's counter flashing set into the mortar, which a careful roofer may reuse if it is copper and undamaged. Everything else should be new.

Ask any roofing bid to spell out the flashing scope. A cheap bid that reuses flashing will leak within a few years.

Step Flashing vs. a Bead of Caulk

Done right, a wall joint gets a separate small piece of step flashing under every shingle course, each one lapping the one below like shingles themselves. Water that gets past the shingles rides the metal back out.

The shortcut some installers take is one long strip of flashing, or worse, just a heavy bead of roofing caulk along the joint. Both look fine for a year or two, then the caulk cracks and the strip channels water sideways into the wall.

If you can see continuous caulk instead of layered metal steps where the roof meets a wall, the flashing was done wrong and it will leak. That is a replacement, not a reseal.

Flashing on Metal and Tile Roofs

Metal roofs use their own flashing system: closures, boots, and formed pieces matched to the panel profile. A leak usually means a failed rubber boot or a backed-out fastener, and the fix is $200 to $600.

Tile roofs flash with lead or malleable metal shaped over the tile contours, plus pan flashing in the valleys. Reworking it means lifting and relaying tile by hand, so a chimney reflash on tile runs $800 to $2,500.

On either roof type, hire someone who works that material regularly. Flashing repairs done with asphalt-roof habits fail fast on metal and tile.

Signs Your Flashing Is Failing

Rust streaks on the roof or the siding below a wall joint. Cracked or missing caulk lines along a chimney or a skylight. Lifted or loose metal you can see from the ground with binoculars.

Inside, a stain on the ceiling near a chimney chase, an exterior wall, or below a skylight almost always traces to flashing, not the field of the roof. The EPA mold guidance covers what to do if a hidden flashing leak has already caused mold.

Water in the attic along a valley after heavy rain is a valley-flashing or underlayment failure.

DIY vs. a Roofer

Re-caulking an accessible counter flashing on a low roof, in dry weather, is a reasonable DIY task with a good polyurethane sealant.

Replacing step flashing means removing and re-weaving shingles, which is roofer work. Chimney counter flashing involves masonry tools and is not a beginner job.

A wrong repair here leaks straight into the house, so if the flashing is on a steep roof or at a chimney, hire it out.

How to Keep the Cost Down

First, catch it early. A $250 wall-flashing replacement beats a $2,500 decking-and-ceiling repair after a wet season.

Second, have the roofer check every flashing point during any roof visit, so you replace the near-failures on one trip.

Third, if the roof is within a few years of replacement, plan the flashing into that job. Fourth, ask for the same metal as the roof, and copper at a masonry chimney if the budget allows, since it outlasts everything.

Bottom Line

Budget $300 to $1,500 to replace roof flashing at a chimney, $250 to $1,000 at a wall or valley, and $150 to $400 for a pipe boot. A full reflash with a new roof is $1,500 to $4,000 as part of the larger job.

Flashing causes most roof leaks, so treat a failure as urgent. Replace bad metal rather than caulking it, and if the roof is near its end, do the flashing as part of a replacement. Keep the gutters clear so water is not forced back under the flashing, and fix any active leak at the same time.