Repair of counter-flashing, step pieces and the crown seal where a brick chimney crosses a roof in Fairfield County and lower Westchester.
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A brick chimney crossing a roof is a fixed obstacle the covering cannot close around by itself. Metal flashing carries water over the shoulders and up the sides, and counter-flashing sets into the masonry above it. A chimney repair checks each of those pieces, and the mortar they sit in, then reseals or replaces the part that has let water through.
A chimney is a frequent leak point because it breaks the roof plane with a block of masonry that does not move with the framing. The roof is built of wood and the chimney is built of brick, and the two respond to temperature, wind and settlement at different rates.
On a chimney that has been re-roofed more than once, the masonry and the metal were often detailed separately, and the seam between them is where the trouble starts.
A chimney on a shorefront house gets a closer look than one inland, because the fixings and the edge metal take the wind off the Sound.
Chimney work is high, and masonry is heavy and brittle. Do not stand on the crown or lean a ladder against the stack itself. Set the ladder on the roof's own structure with a helper, or use proper roof access.
The stack is looked at from the ground, from the roof and from the attic, starting with the mortar and the crown at the top. A cracked crown lets water run down the outside of the flue and into the masonry, so it is checked first because it can feed a leak from above.
The technician looks at the metal set into the mortar joint above the roof, and at the groove it sits in. Counter-flashing that is simply laid over the brick, rather than sitting in a cut groove, lets water track behind it.
The pieces that run up each side of the stack and across the back are examined for lapping, corrosion and fixings. Shoulders are the corners where the chimney meets the roof plane, and they are where a step piece most often lifts.
Counter-flashing is reset into a fresh groove, and base flashing is replaced where it has corroded. Fixings are matched to the metal, and the work is kept to the damaged areas. Where the mortar is loose, it is repointed, and the crown is repaired so that water is shed off the stack.
Any mortar work is allowed to cure before the seal is considered done. The technician runs water over the upper side of the stack while someone watches the attic and the wall below, so the repair is tested rather than assumed. The results are explained before the work is closed out.
Chimney flashing is a set of metal pieces that work together: base flashing on the roof, step pieces up each side, and counter-flashing set into the masonry above. Each one has a different job, and a leak usually comes from a gap between two of them.
The base flashing lies under the shingles or tile and turns up against the chimney. The step pieces are woven into the courses at each side so that every row sheds water onto the one below.
The brick itself does not keep water out. Brick is porous, so the seal is always the metal and the mortar joint at the top of it.
A chimney leak tends to show on the wall or ceiling nearest the stack, often on the side where the flashing is worst, and it follows rain that drives against the masonry. A roof leak more often shows along a slope or under a ridge, away from any masonry.
A chimney leak often dampens the framing that runs beside the stack, so the attic check is useful. Dark staining on the chimney chase or on the sheathing next to the brick points toward the flashing, while staining along a rafter far from the chimney points toward the covering.
The timing helps too. A chimney leak tends to follow wind-driven rain and the thaw after snow, when meltwater runs down the slope and reaches the base of the stack.
Brick, stone and metal stacks all need flashing, but the masonry decides how the metal is set. A brick stack takes a groove and a reset; a stone or older stack may need more care with the mortar before any metal goes on.
On brick, the counter-flashing is set into a groove cut in the joint, and the work depends on finding sound mortar to cut into. On older or softer masonry, a repointing job may have to come first so that the metal has something solid to sit in.
A metal chimney or a factory-built flue has its own flashing kit and its own fixings, and it is not repaired in the same way as brick. In those cases the flashing is matched to the flue and to the roof covering, and the technician says so before starting.
The metal should resist corrosion, and it should match or be isolated from the other metals at the junction. Copper, lead-coated copper and terne-coated stainless steel are the materials that federal preservation guidance names for historic roofs.
The National Park Service's preservation guidance calls for corrosion-resistant metal at the junction, ideally at least 26 gauge, and asks that the flashing run at least 12 inches under the roofing where the source is written for tile.
Mixing metals at a junction invites corrosion where they meet, so a repair that changes the metal of one piece usually means checking the others. The fixings are matched to the sheet, and a technician says which metals the repair uses and why.
The price depends on the height and pitch of the roof, the size and number of sides of the stack, and whether the mortar and crown need masonry work as well as metal. It is explained and approved on site before any work starts, and no figure is given here.
A small stack on a low, walkable roof with sound mortar is a short job. A tall stack at the ridge of a steep roof, especially one with slate or clay tile around it, takes longer to reach and more care to lift the covering.
The things found once the flashing is lifted, such as a cracked crown, loose brick, mortar that has to be cut out, or damage to the sheathing under the metal, are the usual reasons a chimney repair grows.
The most common detail is a brick stack with metal set into a groove cut in the mortar joint above the roof, with step pieces running up each side. The groove is the weak point over time, because mortar weathers and the metal can work loose inside it. The repair resets the metal into a sound groove and renews any step piece that has corroded or lifted, rather than covering the joint with sealant.
The crown is the sloped cap of mortar on top of the stack. When it cracks, water runs down the flue and the outside of the masonry, and it can reach the framing without ever touching the flashing. Crown repair is a masonry task that often goes together with flashing work, because a new seal at the base will not keep a cracked crown from feeding water down the stack.
A stack that takes wind off the water needs more attention at its fixings and its edge metal. Clips, nails and the top edges of the flashing are checked more closely, because wind lifts an edge before it tears a sheet. Where the roof has a different covering from the rest of the house, the flashing has to suit both coverings, and the technician says how it has been matched.
Along the shore in Stamford, Greenwich and Norwalk, the east winds that drive surge into the western Sound also load the top of a chimney. The National Weather Service documented that mechanism during Sandy, and the fixings and edge metal around a stack on a waterfront house are worth checking for that reason.
In Greenwich and New Canaan, the larger houses often have more than one stack, and the older estate roofs may carry slate or clay tile around the chimney, where the flashing sits under a different covering. Repair usually beats replacement there, and the flashing is a large share of that work.
Port Chester and the other Westchester towns sit under a different permit and contractor arrangement from Stamford. Before any chimney work that involves masonry or structure, ask your building department which work needs a permit at that address.
Most chimney flashing and repair calls are scheduled the same day when a technician is free, and you approve the price before any work starts.
Not sure if you're covered? Check your ZIP code.
Repair and replacement of the metal at roof-to-wall joints, valleys and openings on older houses across Fairfield County and lower Westchester.
Tracing where water enters a roof, whether it came in with wind-driven rain or meltwater backing up in winter, and repairing that point.
Stopping the heat loss at the eave that builds ice dams, rather than chipping at the ice once the dam has formed.
A written look at covering, flashing, decking and ventilation, used to decide between repair and replacement on Fairfield County roofs.
Sealant can slow a small leak for a season, but it cannot fix a groove that has crumbled or metal that has lifted. Sealant spread over a failed joint also hides the failure from the next person who looks. The technician decides whether a seal is enough or whether the metal has to change, and says why.
They are different pieces of the same detail. The crown is the cap at the top of the stack, and the flashing is the metal at its base. A cracked crown lets water run down the flue and the outside of the brick, while failed flashing lets water in at the sides. Often both are checked on the same visit.
Stamford's building department publishes guidance that ordinary repairs to structures do not need a permit, and it keeps a list of exempt work. Repointing or any structural change is a different question. Ask the building department for your city or town, because each office sets its own rule, and the permit guide explains the Stamford track.
Water tracks along the framing and the sheathing before it drops, so it can reach a wall or ceiling several feet from the opening. The stain is therefore a poor guide to the source on its own. A technician traces it back through the attic before deciding where the leak starts.
Flashing problems rarely require a new chimney. The masonry is checked for sound mortar, crown and brick, and a repair is recommended where the stack is sound. Replacement is a separate decision, and it is only raised when the inspection shows the masonry itself has failed.
Yes. Meltwater from an ice dam can back up behind the counter-flashing and run into the joint from below, and snow sitting against the uphill side of a stack can melt through a thaw. The ice dam page covers how an ice dam forms, and the ice dam guide explains what to look for at the eave.