Chimney Flashing Repair

Chimney Flashing Repair

Flashing is the metal that bridges the joint where the chimney passes through the roof. It is the single most common source of a water stain that appears on the ceiling beside a chimney rather than on the chimney breast itself, and it is the detail most often done badly, because doing it properly takes more time than sealing it does.

Free estimates, no obligation. Call (888) 882-2070.

How Flashing Is Supposed to Work

Correct chimney flashing is not one piece of metal. It is a layered assembly, and each part has a job:

• Step flashing, individual L-shaped pieces running up each side of the chimney, one per roof course, each lapped over the one below and woven into the roofing. Water runs down the roof, hits a step, and is carried out over the surface.
• Counter flashing, the piece that laps over the top of the step flashing and is let into the masonry. This is the critical one, and the reason is below.
• Base or apron flashing at the downslope face, taking the water arriving from above the chimney.
• A cricket (or saddle) behind a wide chimney on a sloped roof, a small peaked structure that splits water and sends it around either side instead of letting it pond against the back wall.
• Kick-out flashing where the chimney or a roof plane meets a wall, diverting water out onto the roof instead of letting it run behind the cladding.

The assembly works by lapping and gravity, not by adhesion. Every joint is arranged so that water meets an overlap on its way down. Done that way it keeps working after sealant has long since failed, which in Florida is a matter of a few years, not decades.

The single most common defect

Counter flashing should be cut into a mortar joint, a reglet, with the metal turned into the slot and sealed there. What is frequently done instead is to lay the metal flat against the face of the brick and run a bead of caulk along the top edge.

That surface bead is now the only thing between the weather and the roof deck, and it is a consumable. Florida UV and daily thermal cycling harden and shrink it far faster than a northern climate does. When it goes, and it will, water runs straight down behind the flashing. If your chimney was flashed this way, the leak is not a maintenance failure; it was designed in.

How to Tell Flashing Is the Problem

The symptom pattern is more diagnostic here than anywhere else on a chimney:

• A stain on the ceiling beside the chimney, not on the breast. Water entering at the flashing runs along the roof deck or a rafter before it drops, so it surfaces a foot or two away. Water coming through the crown or the masonry face shows up on the chimney.
• Only in heavy or wind-driven rain, never in a light shower. Storm rain arrives sideways and under pressure, getting behind laps and drip edges that shed vertical rain perfectly well. This is also why a contractor visiting on a dry day may not reproduce it.
• Visible caulk along the top edge of the flashing, particularly cracked, shrunken or repeatedly re-applied caulk. Layers of successive caulk repairs are a reliable sign the underlying detail is wrong.
• Rust staining or perforation on the flashing metal, common on galvanized flashing and worse near the coast.
• No cricket behind a wide chimney on a sloped roof, with debris and staining collected against the back wall, the marker of water standing where it should have been diverted.
• Lifted, loose or missing step flashing, or flashing that was face-nailed through its surface rather than concealed by the lap above.

Rule out the roof first

A roof problem within a few feet of the chimney produces exactly the same ceiling stain, because water travels along the deck before it drops. Establishing which one it is comes before quoting either, and it is the cheapest step in the whole job. Paying for chimney flashing when the roof was the source is a common and entirely avoidable outcome.

Tile Roofs Change the Job

This is where most national flashing advice stops being useful in Florida. Barrel and flat concrete tile roofs are everywhere here, and flashing a chimney on tile is a different piece of work from flashing one on asphalt shingle.

Tile cannot be woven course by course the way shingle can. The detail relies on pan flashing set under the tile, tile being lifted and reset, and sometimes cut, around the chimney, and mortar or foam bedding being reinstated afterwards. Tiles are brittle, especially older ones, and breakage during removal is normal rather than exceptional, so replacements have to be matched or salvaged.

Two practical consequences. First, a tile-roof flashing job costs meaningfully more than the same job on shingle, and a quote that does not distinguish them has not been priced from the actual roof. Second, anyone flashing a tile roof by bedding metal in mortar and caulking the edges is applying a shingle-roof shortcut to a tile roof, which fails faster than either done properly.

Materials

Aluminium is the common choice and generally reaches twenty years or more inland. Within a few miles of the coast, salt shortens that noticeably.

Copper lasts forty years or more, is the appropriate choice on a coastal or high-value property, and costs considerably more. On a tile roof, where reflashing means disturbing tile again, the longer service life is worth more than the same upgrade would be on shingle.

Stainless steel sits between the two on cost and handles salt well.

Galvanized steel is the budget option and the reason a good proportion of reflashing jobs happen. It is the metal you find rusted through.

The wider point: method matters more than material. Copper caulked to the face of the brick will leak long before aluminium correctly let into a mortar joint.

Why Florida Flashing Fails Sooner

• Wind-driven rain, June to November. The dominant mechanism. Sideways rain under pressure defeats laps that handle vertical rain without difficulty.
• UV and thermal cycling. Any detail depending on sealant has a much shorter life here. This is the reason the reglet matters so much more in this climate.
• Salt air. Corrodes aluminium and galvanized flashing, and attacks fasteners from behind where nothing is visible.
• Humidity. A roof deck that gets wet does not dry between events, so a slow flashing leak rots sheathing and framing continuously rather than seasonally.
• Ice damming and freeze-thaw are not factors here, and they are what most flashing guidance online is written around. A diagnosis leaning on either is a script from another climate.

Time It With the Roof

Worth saying plainly, because it can save real money: if the roof is within a few years of replacement, flashing is best done as part of the reroof. Flashing is integral to the roof covering, so replacing it means disturbing the roof surface either way, doing it twice pays for that twice. Conversely, a new roof installed over old flashing, or with flashing reused rather than renewed, is a leak already scheduled. If a roofer proposes keeping existing chimney flashing on a reroof, ask why.

Where the masonry the counter flashing has to cut into is itself decayed, the reglet has nothing sound to key into, and brick and mortar repair comes first. If water has been getting in long enough, also check the crown, a chimney neglected long enough to fail at the flashing is rarely sound at the top, and leak diagnosis covers all six entry points.

What Drives the Cost

Flashing a narrow chimney through a low-pitch shingle roof and flashing a wide chimney through barrel tile are not the same job, and both are sold under this name. The small version renews step and counter flashing where the mortar takes a reglet cleanly and the roof surface weaves back around it. The large version means lifting, cutting and resetting tile with breakages matched, building a cricket behind the chimney, repointing the masonry the reglet keys into, and replacing rotted sheathing at the penetration.

What the chimney decides

• The roof covering. Tile cannot be woven course by course like shingle, so it is lifted, cut and reset, with brittle older pieces breaking as a matter of course. A quote not distinguishing tile from shingle was not priced from your roof.
• Width and pitch together. They decide whether a cricket is needed behind the stack, which is a structure built on the roof, not another piece of metal.
• What the metal is fixed to. Counter flashing has to be let into a mortar joint, so decayed masonry means repointing before the reglet has anything to key into. Rotten sheathing at the penetration is separate work again, the usual reason a figure moves once the old flashing is off.

What you decide

• The material. Aluminium, stainless and copper are three levels of cost and three service lives, and near salt water the cheaper metals corrode fastest. On tile, longer-lived metal is worth more, because reflashing later disturbs tile again.
• How much of the assembly is renewed. Replacing only the failed side is cheaper today. Renewing step, counter and base together leaves the whole detail the same age.
• Whether to wait for the reroof. If the roof is within a few years of replacement, doing the flashing as part of it avoids disturbing the roof surface twice. Often the largest saving here.

Almost none of that is visible from the ground, some of it not until the old flashing is off. So the crew gets on the roof, establishes whether the source is the flashing or the roof itself, checks the mortar and whether the chimney needs a cricket, then leaves a free written, itemised estimate naming the detail and the material. A phone figure would have to assume a roof covering, a chimney width and sound sheathing, and being wrong about any one of the three changes the job.

What to Ask Before You Hire Anyone

• Is the counter flashing being cut into a mortar joint, or caulked to the face? The single question that predicts whether this repair lasts.
• Have you ruled out the roof as the source?
• Does my chimney need a cricket, and is one included?
• What material, and why that one for my location?
• On a tile roof: how are you handling tile removal, breakage and replacement?
• How old is the roof, should this wait and be done with the reroof? An honest answer here tells you a lot about who you are dealing with.

Free estimates, no obligation, call (888) 882-2070. We will get on the roof, establish whether it is the flashing or the roof, and put the detail we are proposing in writing.