Water loves chimneys. A brick or stone mass interrupts the smooth plane of a shingle roof, concentrates wind, and creates eddies where rain, snow, and debris settle. The intersection lines around a chimney are long and full of potential gaps, especially at the uphill side and corners. Good flashing is the difference between a roof that lasts its full service life and interior plaster bubbling within a season. I have torn open enough ceilings and rebuilt enough rotted sheathing to know that most leaks blamed on “bad shingles” trace back to inadequate or improperly sequenced flashing at the chimney.
Flashing around a chimney is not one detail, it is a system: base flashing, step flashing along the sides, counterflashing into the masonry, and a saddle or cricket on the high side if the chimney is wide enough. Those pieces must be sized, overlapped, and integrated with the shingle roof in a way that directs water back onto the surface of the roof, never behind it. The material matters, though not as much as the sequencing. Get the order right, and ordinary galvanized steel will last years. Get it wrong, and even copper will fail.
What a Dry, Durable Chimney Intersection Needs
A shingle roof sheds water by laps and gravity. Flashing around a chimney must respect that. The roof deck, underlayment, shingles, and flashing should layer like fish scales, from bottom to top, so any water that gets under one layer is directed onto the layer below, then out. Anything that breaks that path creates a trap.
A complete assembly includes several components working together:
- Base flashing at the front of the chimney that turns onto the roof and up the masonry, catching water flowing toward the downhill edge. Step flashing pieces along each side, interleaved with each course of shingles. Each piece turns up the chimney and out onto the roof surface. Back pan, also called head flashing, at the uphill side. If the chimney is more than 24 inches wide across the roof slope, a cricket or saddle divides flow and stops snowpack from sitting and melting into the joint. Counterflashing cut into the masonry, overlapping the turned-up legs of the base, step, and back pan flashings. This is the primary waterproof cover over the vertical legs. Underlayment and, in snow or ice areas, an ice and water barrier running up the roof and tying into the flashing edges.
When leaks appear, they almost always stem from a break in this sequence, missing counterflashing, or corners that were never sealed properly. Roofing cement smeared over a joint is not a substitute for metal and proper laps. It sometimes buys a season, then cracks and channels water exactly where you do not want it.
Materials That Hold Up and When to Use Them
On a shingle roof, the common flashing materials are galvanized steel, aluminum, and copper. Stainless steel appears occasionally in coastal work, and lead shows up in older homes, especially in the Northeast.
Galvanized steel is the workhorse. It is affordable, easy to bend cleanly, and readily available in the dimensions needed for roof shingle installation. Go heavier than the minimum. I prefer 26 gauge for step flashing and back pans. It takes fasteners well and does not dent as easily during shingle roof repair.
Aluminum is tempting because it is light and cheap, but it does not play well against masonry or pressure-treated lumber. Mortar salts and copper-arsenate chemicals can corrode it. If you must use aluminum, isolate it from wet mortar and treated wood, and keep it thick enough to avoid kinking during installation.
Copper is excellent and long lasting. It costs more, and it requires a little more care in forming crisp bends without stretching the metal. On historic homes or in premium projects where roof shingle replacement is planned with a 30 to 50 year horizon, copper earns its keep. It pairs well with brick chimneys and looks right as it patinas.
Lead can still be excellent for counterflashing because it can be dressed into joints, especially around rough stone. It should not contact bare aluminum. In freezing climates where thermal movement is extreme, lead’s malleability helps the flashing move without tearing.
Fasteners matter. Galvanized or stainless steel nails for steel flashing, copper nails for copper. Do not mix metals. Nails should be long enough to penetrate the roof deck at least 3/4 inch. Sealants are not a primary defense but can reinforce corners. Use high-quality butyl or polyurethane sealant, not generic roofing tar. Cement has its place, primarily to bed the front base flashing tab or seal a cut corner, not as a broad, smeared membrane.
Preparing the Roof and Chimney
Before touching metal, inspect the chimney. Look for spalled brick faces, powdery mortar, loose crowns, missing flue covers, and step cracks. Flashing is only as good as the masonry it ties into. If a brick can be wiggled by hand, it will not hold counterflashing. Repoint soft joints and repair the crown. Make sure the chimney projects high enough above the roof per code and draft requirements. If the stack is too short, eddies will dump water and snow into the uphill corner endlessly.
Strip shingles back at least 18 to 24 inches around the chimney. On shingle roof repair jobs, I often find two or three layers packed tight to a chimney face, with nails driven within an inch of the brick. Remove all nails and debris. Replace any punky or delaminated sheathing. Set a straightedge and confirm that the deck is flat, without a belly that will pond water at the back pan.
Underlayment matters. Run the roof underlayment up to the chimney first. In cold climates, I run an ice and water barrier 18 to 24 inches up the roof from the eave and extend it both sides past the chimney. Along the uphill side, I bring a strip of ice and water barrier 6 to 12 inches up the chimney face. The membrane should never be the only barrier, but it buys safety during the first thaw and during wind-driven storms.
Plan the layout. If you are doing roof shingle installation from scratch, you can engineer shingle courses to land cleanly at the chimney edges, minimizing small slivers and awkward step flashing. If you are in roof shingle replacement mode, accept what the deck gives you, but aim for full-width step pieces and clean reveals.
Base Flashing: Starting at the Front
At the downhill edge, install a base flashing that extends 4 to 6 inches onto the roof surface and at least 4 inches up the chimney face. If you are working on a low-slope shingle roof, increase the horizontal leg to 8 inches. The bottom edge of this base flashing should sit over the top of the course of shingles just below the chimney. I bed the lower 2 inches in a thin, continuous bead of roofing cement, then press into place to prevent wind-driven water from wicking back. Keep the cement thin and consistent to avoid creating a hump.
The side legs of the base flashing should return a bit up each chimney corner. Cut the base flashing to wrap around the bottom corners tight, then notch so the side step flashing can overlap cleanly later. Avoid crushing the metal into the brick, you want crisp angles and tight contact without distortion.
If the roof has closed-cut valleys dumping directly at the chimney, consider extending the base flashing wider or folding a diverter tab to steer water away. Do not create a hard dam that catches debris. The goal is redirection, not blockage.
Step Flashing: One Course at a Time
Step flashing pieces should be individual L-shaped pieces, not a continuous run. Each piece typically measures 8 inches by 8 inches, bent in the middle at 90 degrees. Some installers use 7 by 7 or 5 by 7 for smaller shingles, but I find 8 by 8 gives generous cover and flexibility. The vertical leg should run up the chimney a minimum of 4 inches, more if the exposure is harsh or the roof pitch is low.
As you shingle up the side, set each step piece on top of the shingle course, with the horizontal leg extending at least 4 inches onto the shingle surface and the vertical leg tight to the chimney. Nail only on the roof deck, high on the horizontal leg, far enough from the vertical bend that the nail head will be covered by the next shingle course. Never nail the flashing into the chimney. Each subsequent shingle course covers the preceding step piece, and each new step piece overlaps the one below by at least 3 inches. The laps should always shed toward https://maps.app.goo.gl/LufjBcSTLAKTs1mg8 the downhill side, so any small amount of wind-blown rain that reaches the overlap still flows out.
At the lower corner, the first step piece is often where leaks start. I cut and fold a small kick at the end of the base flashing to prevent water running along the side of the chimney from curling around the corner and back under. A dab of butyl at this lap helps, applied sparingly.
Take care with exposure. If your shingles are at a 5 inch exposure, the vertical offset of each step piece will be 5 inches as you move up the side. Keep the reveal consistent, and ensure the step flashing top edge is always covered by the shingle above by at least 2 inches.
The Back Pan and Cricket
The uphill side is the most vulnerable area. Snow drifts against it and melts slowly, soaking the joint for days. On chimneys that measure more than 24 inches across the roof slope, a cricket is not optional. It splits the flow and keeps water moving. Even on narrower stacks in heavy-snow regions, I favor a small saddle. It reduces the dead pocket where leaves and needles collect.
Frame the cricket with 2x lumber tied into the roof deck. The ridge of the cricket should pitch at least as steep as the main roof, and often a bit steeper to shed water aggressively. The slope should carry water to the sides without creating a flat where ice can dam. Sheath it with plywood or boards to the same thickness as the roof, and wrap with underlayment. On ice-prone roofs, run ice and water barrier over the entire saddle and 6 to 12 inches up the chimney.
The back pan flashing runs across the uphill face of the chimney and extends out onto the roof on both sides far enough that the next step flashing pieces can overlap it by at least 4 inches. For steel, I use a single piece if possible, often 26 gauge, with the vertical leg 6 to 8 inches up the chimney and the horizontal leg at least 8 inches onto the roof. On wide chimneys or where the sheet size limits a single piece, I join with a standing seam at the center, standing the seam away from the ridge of the cricket so it sheds water. Avoid flat lap joints on the back pan unless you can hem and lock them mechanically.
Where the back pan meets the side step flashing, the laps need to be clean. The back pan should tuck under the counterflashing and over the last course of shingles, but the side step pieces above will sit on top of the back pan’s edges. Think of shingling the metal itself: water coming down the chimney face hits the back pan and is directed to the sides, where it rides over the pan and onto the step flashing, then onto the shingles.
If you are not installing a cricket on a small chimney, still use a generous back pan, and consider a slight break in the metal to form a subtle ridge at the center. The ridge helps direct water to the sides instead of letting it wander back toward the chimney corners.
Counterflashing Into Masonry
Counterflashing is the cap that keeps water from running behind all the step, base, and back pan legs. Surface-applied metal with a bead of caulk at the top does not last. Proper counterflashing is inserted into a reglet cut into the mortar joint or brick.
Pick a horizontal mortar joint at least 8 to 12 inches above the roof line on the sides, and as high as reasonably possible above the back pan. Use a grinder with a diamond tuckpointing blade to cut a clean kerf 1 inch deep along the joint. Vacuum dust as you cut. On old chimneys with soft lime mortar, be gentle and avoid breaking brick corners.
Form counterflashing pieces with a 1 inch return that tucks into the reglet. The vertical drop should cover the upturned legs of the base, step, and back pan by at least 2 inches. For brick, a saw-toothed counterflashing looks neat and follows the course lines, but straight runs work just as well if you plan your joints. Set the counterflashing into the reglet with a bend that wedges it, then pin with lead wedges or stainless springs. After it is fully seated, pack the kerf with a non-sag sealant made for masonry, or use lead wool for a traditional pack, then tool a slight drip edge into the sealant. The goal is to lock the counterflashing mechanically, then seal the reglet. The counterflashing should hang freely over the step flashing, not be riveted to it. Movement is normal, and a free overlap keeps the system from tearing under thermal cycles.
On stone chimneys with irregular faces, sheet lead or malleable copper helps you dress the counterflashing to the surface. Avoid chasing every dip; keep a clean vertical drop and step over large protrusions with small formed saddles. Where a stone projects far, you can cut small chases into the stone itself, but this adds time and risk. Sometimes a carefully installed surface reglet with a lead plug holds better than fighting for a perfect stone joint.
Sequencing Is Everything
After you repair enough leaks, you learn to think four steps ahead. Try to force the flashing onto the roof as a single afterthought, and you end up with exposed edges and trapped water. Set out the components near the chimney and visualize the flow: rain hits the uphill counterflashing and back pan, splits, and runs to the sides. The step flashing and shingles alternate in a stair-step pattern that always sheds downhill. The base flashing at the front dumps water back onto shingles that run past and over it, never into a seam pointed uphill.
Even small inconsistencies, like a step piece that is 2 inches shorter than its neighbor, can create a point where a wind-driven gust pushes water backward. Keep laps consistent. Keep fasteners high and away from bends. If you find yourself reaching for extra roofing cement, stop and reconsider the sequence. Most of the time the right overlap eliminates the need for goop.
Common Mistakes and What They Cost
I see the same errors over and over on shingle roofing projects that arrive on the repair list after a storm.
Nailing flashing to the chimney or through the vertical leg is a cardinal sin. The nail hole opens with movement, and the leak is hidden until it has done damage. Rely on counterflashing to hold the vertical legs down.
Running a single, long side flashing instead of individual step pieces leads to leaks. Continuous side flashing creates long horizontal laps that invite capillary pull.
Shingles butted tight to the chimney without room for flashing are trouble. Always leave a small gap between the shingle edge and masonry so water has a defined channel and debris does not bridge. A quarter inch is usually enough.
Overreliance on caulk or roofing tar masks poor sequencing. Sealant fails sooner than metal. If the design depends on a bead of goo to keep water out, it is not a reliable design.
Skipping the cricket on a wide chimney is false economy. The initial savings disappear the first time a heavy snow load sits against the back pan and finds a pinhole. Rebuilding ceilings and insulation costs far more than framing a small saddle during roof shingle installation.
Integrating With Different Shingle Types and Roof Pitches
Not all shingle roofs are equal. Three-tab shingles give predictable courses and clean step flashing reveals. Laminated architectural shingles have variable tabs and thickness, which can hide step pieces if you are not careful. With thick laminated shingles, use slightly taller step flashing, 8 by 10 for example, to ensure the top edge is buried under the thicker headlap.
On low slopes, water moves slowly and in greater volume. Increase horizontal legs of flashing to 8 inches and be especially attentive to laps. Add an extra course of ice and water barrier around the chimney on the uphill side. On steeper roofs, wind is the enemy, lifting shingles and pushing rain sideways. Keep nails on the high side, and consider hemmed edges on the back pan to stiffen it against flutter.
In coastal zones, salt accelerates corrosion. Copper or stainless steel makes sense for both flashing and fasteners. If you work with a shingle roofing contractor near the ocean, ask to see examples of five-year-old chimneys they flashed. The metal should still present clean bends and tight edges, not chalky residue or pitting.
Repairing Versus Replacing Flashing During Shingle Work
When a homeowner asks for shingle roof repair around a leaky chimney, I weigh the age of the roof against the condition of the flashing. If the shingles around the chimney are in good shape and the flashing system is modern but has a discrete failure, a surgical repair can be justified. Examples include a cracked solder joint on a copper back pan, a torn corner at the base flashing, or missing counterflashing clips. In those cases, I remove only what is necessary, correct the metal, and reweave shingles.
If the roof is nearing the end of its life or if the step flashing is buried under multiple shingle layers, replacement is the smarter choice. You cannot reliably tie new counterflashing into old, underlapped step pieces. During roof shingle replacement, I always plan to redo the entire chimney flashing system. It is cheaper to do it right while the roof is open than to return later for a leak that started where old and new met at a corner.
When dealing with historic roofs, respect the original material choices. Copper on a 100-year-old chimney pairs with copper. If you must transition, do so with a deliberate break and compatible solder or mechanical seam, not a mixed metal contact that will create a galvanic cell.
The Role of Maintenance
Even the best flashing deserves a periodic look. Chimneys are vertical, and vertical surfaces shed water but collect leaves at their base. After leaf drop, check the uphill side for debris packed against the counterflashing. Clear the channel so water can move. Inspect the masonry above the counterflashing for new cracks or soft joints. Mortar erodes over time, and a gap above the reglet will channel water behind the flashing regardless of how well the lower parts were built.
Look for telltale signs inside the attic: darkened sheathing around the chimney, rusty nail tips, or a musty smell after a storm. An hour with a flashlight underneath can save a day of tear-out later. Small interventions, like a new sealant pack in the reglet, can extend the life of an otherwise sound system.
If you have a wood-burning appliance, your chimney heats and cools more than one serving only as a chase for a metal flue. The heat drives expansion cycles that test flashing movement. A loosely overlapped counterflashing with good clearance handles this. A tight, riveted joint does not.
A Brief Field Checklist Before You Pack Up
- Verify all vertical legs of flashing are covered by counterflashing and free to move without binding. Confirm laps on step flashing are consistent, with at least 3 inches overlap and nails only on the horizontal legs. Check the uphill side for a properly framed and flashed cricket if the chimney spans more than 24 inches across the slope. Inspect reglets for full depth and intact sealant or lead pack, with counterflashing seated and wedged. Flush test with a garden hose, starting low and moving up, watching for any seepage inside.
When to Call a Specialist
Some chimneys demand more than standard roof skills. Tall stacks with elaborate corbeling, fieldstone with irregular joints, or chimneys that straddle ridges require custom metalwork. A seasoned shingle roofing contractor who also fabricates metal in-house can tailor a cricket, form pan flashings with lock seams, and detail counterflashing that aligns with the masonry courses. If your project involves slate or tile adjacent to shingles, or if you are tying into copper valleys, bring in a roofer who understands mixed-material transitions. The cheapest bid on paper often omits this craftsmanship, and the difference shows up in your ceiling after a nor’easter or a spring thaw.
Homeowners juggling roof shingle repair and interior work sometimes want to postpone chimney flashing upgrades. I have seen what that costs. Water finds the weakest link. Spend the time on proper sequencing, material choices that match the environment, and small adjustments like a correctly pitched cricket. The roof will repay you by staying out of sight and out of mind. That is the highest compliment a shingle roof can earn.
Express Roofing Supply
Address: 1790 SW 30th Ave, Hallandale Beach, FL 33009
Phone: (954) 477-7703
Website: https://www.expressroofsupply.com/
FAQ About Roof Repair
How much should it cost to repair a roof? Minor repairs (sealant, a few shingles, small flashing fixes) typically run $150–$600, moderate repairs (leaks, larger flashing/vent issues) are often $400–$1,500, and extensive repairs (structural or widespread damage) can be $1,500–$5,000+; actual pricing varies by material, roof pitch, access, and local labor rates.
How much does it roughly cost to fix a roof? As a rough rule of thumb, plan around $3–$12 per square foot for common repairs, with asphalt generally at the lower end and tile/metal at the higher end; expect trip minimums and emergency fees to increase the total.
What is the most common roof repair? Replacing damaged or missing shingles/tiles and fixing flashing around chimneys, skylights, and vents are the most common repairs, since these areas are frequent sources of leaks.
Can you repair a roof without replacing it? Yes—if the damage is localized and the underlying decking and structure are sound, targeted repairs (patching, flashing replacement, shingle swaps) can restore performance without a full replacement.
Can you repair just a section of a roof? Yes—partial repairs or “sectional” reroofs are common for isolated damage; ensure materials match (age, color, profile) and that transitions are properly flashed to avoid future leaks.
Can a handyman do roof repairs? A handyman can handle small, simple fixes, but for leak diagnosis, flashing work, structural issues, or warranty-covered roofs, it’s safer to hire a licensed roofing contractor for proper materials, safety, and documentation.
Does homeowners insurance cover roof repair? Usually only for sudden, accidental damage (e.g., wind, hail, falling tree limbs) and not for wear-and-tear or neglect; coverage specifics, deductibles, and documentation requirements vary by policy—check your insurer before starting work.
What is the best time of year for roof repair? Dry, mild weather is ideal—often late spring through early fall; in warmer climates, schedule repairs for the dry season and avoid periods with heavy rain, high winds, or freezing temperatures for best adhesion and safety.