Roof Flashing Repair in North New Jersey

Strip away the names and every piece of flashing obeys one rule: each layer laps over the top edge of the layer below it, so gravity carries water out and down and never behind. Roofers call it shingle-fashion, and it is the whole theory. A flashing is not a seal. It is geometry — bent metal arranged so water arriving at a joint is handed to the next surface downhill and given nowhere else to go. Sealant belongs in a correct detail only as a secondary component at a termination, never as the thing holding the water out.

That rule is also the diagnosis, because flashing fails in two ways and both are versions of breaking it. Either a piece is absent, leaving a gap in the chain where water is handed to nothing, or a piece is lapped the wrong way, so an upper layer tucks under a lower one and the assembly funnels water inward. Both can sit under a roof that looks immaculate from the street, and both are usually found only because a ceiling went brown.

Roof-to-wall metal all gets called step flashing, but the junction uses different pieces depending on which way the roof runs, and mixing them up is how the detail gets built wrong. Step flashing is the sidewall condition, where the slope runs alongside the wall and climbs it: individual L-shaped pieces, one per shingle course, each lapped by the piece above and each handing water onto the shingle below. Apron or headwall flashing is the other condition, where the top of a roof plane runs uphill into a wall — continuous bent metal, carried up behind the wall's water-resistive barrier and lapped down over the covering.

One nuance worth having before you argue with a bidder, because the code is looser here than most homeowners are told. R905.2.8.3 of the 2021 IRC says base flashing against a vertical sidewall shall be continuous or step flashing, not less than four inches in height and four inches in width, and shall direct water away from the sidewall onto the roof or into the gutter. Continuous is permitted. So a single long strip up a pitched sidewall is not automatically a violation, and we would rather tell you what we do than tell you what an inspector will fail. On a slope we run individual step pieces course by course, because a continuous vertical leg on a pitched wall stakes the whole junction on one unbroken top-edge seal and on shingles that never move — and both of those assumptions expire.

Whichever piece the geometry calls for, its vertical leg has to be covered by something. On a sided wall the cladding and the drainage plane behind it do that, which is why the assembly lives under the siding and why it is so routinely disturbed by trades who never touch a roof. On masonry the covering layer is a formed counter-flashing let into the wall itself — chimney work, with a page of its own. The rule to hold onto is that the wall's drainage plane must end on top of the flashing's vertical leg, never behind it.

Two more members of the family get treated as accessories and are neither. Drip edge is the L-shaped metal that terminates the roof at the eaves and rakes, and R905.2.8.5 is unusually specific about it for a code section: required at both eaves and rakes of a shingle roof, adjacent lengths lapped not less than two inches, the metal extending not less than a quarter inch below the sheathing and not less than two inches back up onto the deck, fastened at not more than twelve inches on center. Then the sequence, which is the part rushed jobs reverse: underlayment goes over the drip edge along the eaves, and under the drip edge along the rakes. Backwards, and you have built a path into the fascia instead of a barrier against it.

What the code does not say — and what we do anyway — is that the eave drip edge should project far enough that its lower leg discharges inside the gutter trough. Code asks only for that quarter inch past the sheathing, and a quarter inch on a house whose fascia has settled is exactly how water ends up running behind the gutter and down the board. It is the most common reason a fascia rots under a roof that never leaked into the house at all.

Pipe boots and vent collars are the field's small holes. A plumbing vent gets a flanged boot whose base is woven into the courses like every other flashing here — top edge under the course above, bottom edge over the course below — with a flexible collar sealing to the pipe. The flange rarely fails. The collar hardens, cracks and finally lets go, usually well inside the life of the shingles around it, and a split the size of a coin leaks like something far more serious.

Not every failed flashing is a rebuild. If the metal is sound — not perforated, not deformed, not eaten through where packed debris held water against it — and what failed is a top edge that pulled away, it can often be re-dressed, re-secured and re-sealed without disturbing the roof covering at all. That is the smaller, cheaper, correct fix, and when it fits we do it and say so.

Step flashing is the one that surprises people. Each piece is fastened and then captured by the shingle course laid over it, so there is no way to replace a run of step flashing without lifting the courses above it. Replacing step flashing is a shingle job as well as a metal job, every time. That is worth knowing when you read a proposal: a bidder who says he will replace the step flashing along your dormer without touching a shingle is not describing a flashing replacement.

Which brings us to the failure that brings us back to the same house twice. Caulk and roofing tar are sacrificial materials with a service life measured in a handful of North Jersey summers, and in a leaking joint they are asked to do a job that geometry is supposed to do. Sealant over a missing or reversed flashing is a countdown, and it hides the defect while it runs: by the time the bead fails, the metal under it has been wet for years and the deck under that has often gone soft. When we find a tar patch, the first job is getting it off so the metal underneath can be judged honestly.