Repair Damaged Roof Flashing

Goal

Repair specific flashing failures without full reroofing. Common failures: step flashing at walls, counter-flashing at chimneys, pipe boots, valley flashing. Each requires a different approach.

Prerequisites

• Replacement flashing material (aluminum, galvanized, or matching original)
• Poly urethane roof caulk
• Pry bar, snips, hammer, screws
• Replacement shingles for areas disturbed during repair
• Helper for ladder work
• 1-3 hours per repair

Repair scenarios

Scenario 1: Step flashing lifted/damaged

Symptom: leak at sidewall (where roof meets vertical wall)

Steps:

1. Lift shingle courses above + adjacent to damaged step flashing
2. Pull damaged step flashing
3. Inspect: rusted? bent? cut wrong? Note cause
4. Cut new step flashing pieces (5" × 7" L-shape typical, bend in middle)
5. Slip new step flashing back under the next course up, against the wall
6. Repeat for any other damaged pieces (one step per course)
7. Inspect counter-flashing above - re-seal at wall if loose
8. Replace any damaged shingles
9. Nail all back in place

Verify: spray water at the wall + roof intersection; helper checks attic for water

Scenario 2: Counter-flashing pulled out of mortar (chimney)

Symptom: leak around chimney, especially after wind-driven rain

Steps:

1. Inspect counter-flashing: rusted, bent away, completely missing?
2. If still attached but loose: chase the mortar joint with a grinder OR small chisel; re-seat counter-flashing edge; refill mortar joint
3. If pulled out completely: replace

• Bend new counter-flashing (J-shape)
• Cut into mortar joint 1.5-2 inches deep
• Insert counter-flashing top edge into the cut
• Refill mortar joint with masonry sealant

1. Caulk vertical seam at chimney corners

Common mistake: sealing TOP edge of counter-flashing with caulk only - caulk fails in 2-3 years. Mortar/masonry sealant is the correct seal.

Scenario 3: Pipe boot cracked/failed

Symptom: leak around plumbing vent pipe

Steps:

1. Cut sealant around old pipe boot
2. Lift shingle courses around boot to expose base flashing
3. Remove old boot (slip up + off pipe)
4. Inspect pipe stub: rotten/rusted? Replace if needed
5. Install new boot (slip down over pipe)
6. Boot base sits on top of shingle below the pipe; shingles above lay over the boot base
7. Caulk boot-to-pipe + boot-to-deck (poly urethane)
8. Reset shingles above; nail strip only
9. Re-caulk any disturbed shingles

Premium upgrade: install all-lead boot with rubber gasket (15-25 year life vs 5-10 for cheap rubber)

Scenario 4: Valley flashing damaged

Symptom: leak in valley (where two roof slopes meet)

Steps:

1. Determine valley type (open metal vs closed-cut shingles)
2. If open metal: damaged metal needs replacement

• Lift shingles on both slopes
• Remove damaged metal
• Inspect underlayment (replace ice + water shield if torn)
• Install new valley metal (W-shaped center, 24" wide minimum)
• Re-lay shingles on both slopes, cutting back from valley centerline

1. If closed-cut: damaged shingles need replacement

• Lift shingles in valley
• Inspect underlayment
• Re-cut + re-lay shingles per closed-cut method

Scenario 5: Skylight flashing failure

Symptom: leak at skylight perimeter

Steps:

1. Determine which side is leaking (use hose test if uncertain)
2. Most skylight flashing comes as a kit - get the kit specific to the skylight model
3. Remove old flashing (apron at top, step at sides, sill at bottom)
4. Install new flashing components per manufacturer
5. Re-set shingles around perimeter
6. Caulk overlaps with polyurethane

If skylight is > 20 years old + leaking through the seal (not flashing): recommend skylight replacement, not flashing repair.

Scenario 6: Drip edge missing/damaged

Symptom: water staining on fascia, soffit rot

Steps:

1. Pull back shingles at eave to expose existing condition
2. If no drip edge: install one (L-shape, 1.5" each leg)
3. Drip edge goes UNDER underlayment at eaves (water sheds onto drip edge, then off)
4. Drip edge horizontal leg extends 1/4 to 1/2" over gutter
5. Nail every 8-12" along edge
6. Re-set shingles, ensuring first course extends 1/2 to 1" past drip edge

Scenario 7: Wall flashing on a stucco/EIFS wall

Symptom: leak at wall transition, especially on stucco/EIFS walls

These are trickier because the wall material itself can be damaged:

1. Inspect wall surface for crumbling/cracking at flashing line
2. Re-cut counter-flashing reglet (a saw cut into the wall) if missing
3. Install kickout flashing at terminations (prevents water running down wall + behind siding)
4. Coordinate with painter / wall trade if wall repair needed

Common mistakes

• Sealant instead of flashing: caulk fails in 2-3 years; flashing should outlast roof
• Wrong material: aluminum at copper = galvanic corrosion; match the metal
• Skipping ice + water shield in valleys: leak in winter despite valley repair
• Reusing rusty step flashing: false economy; replace
• Forgetting kickout flashing: water runs down wall, behind siding, rots framing
• Caulking over rust: rust continues underneath; flashing fails
• No counter-flashing: step flashing tops are exposed; leak in wind-driven rain

When repair is enough vs reroof

Repair OK if:

• Isolated failure
• Surrounding flashing in good shape
• Roof has 5+ years of life remaining
• Customer doesn't want reroof yet

Reroof recommended if:

• Multiple flashing failures
• Roof age 18+ years
• Customer planning to sell home (full system cleaner)
• Flashing failure + significant shingle damage

Safety notes

• Wet roofs cause falls; reschedule
• Counter-flashing work near chimney: watch for crumbling masonry
• Pipe boots: pipes can be hot (vent pipes in summer)
• Cut metal: cut-resistant gloves
• Eye protection for grinding mortar joints

References

• NRCA flashing guidelines
• Manufacturer-specific flashing diagrams
• Manuall internal: Roof Flashing Types + Installation Reference, Diagnose + Repair a Roof Leak