Reseal, patch or reflash? Sizing your flashing job

Four sides, three kinds of flashing job

Flashing manages water where a chimney meets a roof. A shingle-roof arrangement can include an apron, step pieces, an uphill detail and counterflashing. Tile and metal roofs can use different systems. The correct assembly depends on both the roof and chimney construction.

A leak may involve one joint or a wider flashing assembly. Access, roof covering, underlying condition and the appropriate detail affect the work and schedule. A small visible opening does not establish that the repair will be brief or limited to sealant.

Resealing, the smallest of the three

Is the metal itself still sound, well fastened and free of rust? Then the problem may just be the sealant where the counter flashing meets the brick. That bead dries, shrinks and cracks over the years, and water follows the crack down behind the metal.

A reseal means cutting out the old sealant, cleaning the joint and laying in a new bead of a sealant rated for masonry and metal. It's the most affordable fix on the list, and it's maintenance more than a cure. If the joint behind it is crumbling, or the metal has lifted, new sealant won't hold for long.

Patching or refastening one side

The middle job fixes one side while leaving the others alone. A counter flashing the wind pried loose gets reset and fastened. A few rusted step pieces along one side come out and new ones go in, slipped under the shingle above each course the way the originals were.

This works when the other three sides pass a close look. It fits the case where a single storm lifted one edge, or when an old repair on one face was done with tar and caulk that finally gave up. The price sits between a reseal and a full job, and it climbs with how many shingles have to be lifted to reach the damaged pieces.

Chimney flashing replacement cost for all four sides

Some roof and chimney arrangements require a cricket to divert water around the uphill side. Its need and design depend on the roof, chimney and applicable requirements. Have the contractor identify that scope rather than relying on a single width rule from a general guide.

A full job strips the old flashing, checks the roof deck beneath it and installs a new apron, new step flashing up each side, one piece per shingle course, a new back pan and new counter flashing. The counter flashing is set into a groove cut into a mortar joint, then sealed, so wind can't easily pry it loose. The cost to reflash a chimney also covers the shingles that have to come up and go back down around it.

Have the proposed roof-to-chimney detail checked against the applicable roofing instructions and building requirements. If additional water-diversion work is needed, the estimate should identify its design, responsibility and effect on the surrounding roof.

What moves the price inside each job

Once the scope is set, a handful of things decide where in its range your job lands.

• The roof covering: shingle, tile and metal systems require different details and handling, following the applicable roof manufacturer's instructions.
• The chimney's width and a cricket. A wider chimney means more step pieces and a bigger back pan, and a cricket adds framing and metal, with your quote naming who builds it.
• Height and pitch. A steep or two-story roof needs more protection and staging before anyone touches the flashing.
• The mortar the counter flashing goes into. A groove needs sound mortar, so crumbling joints at that line get repointed first.
• What's under the metal. Rotted roof decking beside the chimney is a roofer's repair, and your quote should say so.

Signs you're past a simple reseal

A few clues tell you the smallest job won't be enough. A stain that grows after every rain, even after someone recaulked the joint, is one. Rust holes you can see from the ground, flashing that flaps in the wind, or counter flashing nailed flat to the brick face with the nail heads showing are others.

Thick black tar smeared over the whole joint is a clue too. It's a sign an earlier repair covered a problem instead of fixing it, and the metal underneath has had years to corrode where nobody could see it.

Planning a new roof? Time the flashing with it

Chimney flashing work may overlap with roofing, decking or masonry repair. Confirm who is responsible for each part, what is included and how concealed damage changes the scope. A particular division between trades or same-day completion should not be assumed.

On a reroof, the roofer handles the roof covering and the underlayment, and our pros handle the counter flashing, the mortar joint it sits in and any masonry repair above the roofline. Agree on who installs the step flashing and the cricket before the tear-off, and ask for that split on both quotes so nothing gets missed or paid for twice.

Flashing may be repaired or replaced around an otherwise serviceable roof when the appropriate method permits it. The condition of nearby materials and access determine the schedule. The estimate should state any roofing work and temporary weather protection needed.

Get your flashing sized for free

Stain by the chimney after every storm? Our family-run, locally owned techs check all four sides of the flashing free of charge and tell you which of the three jobs fits, with a written quote to keep. Your first service receives 10% off. The line for chimney flashing repair is (352) 675-6366.