Roof flashing is the metal that waterproofs every place the roof plane is interrupted — and there are 8 main types, each with one specific job. Step flashing guards walls, valley metal carries concentrated runoff, drip edge protects the deck edge, kick-out diverts water away from siding, and counter flashing caps it all. Flashing failures cause more leaks than shingle failures, which is why knowing the types helps you read a quote — and spot a shortcut. Here is each one, where it goes, and how it fails.
The 8 flashing types at a glance
| Type | Where it goes | How it fails |
|---|---|---|
| Step flashing | Where roof meets a side wall (each shingle course gets its own piece) | Reused during reroof; rusts; sealed with caulk instead of layered |
| Counter (cap) flashing | Over step/base flashing on chimneys and walls | Mortar joint loosens; caulk-only shortcuts |
| Valley flashing (W-metal) | Open valleys where two planes meet | Debris traps water; nails through the center |
| Drip edge | Eaves and rakes, under the underlayment/shingles | Missing entirely on older roofs; wrong overlap order |
| Kick-out flashing | Bottom of a roof-wall intersection, above gutters | Most commonly OMITTED piece — rots siding below |
| Base flashing | Bottom of chimneys and walls, paired with counter flashing | Corrosion at corners and seams |
| Vent pipe boot | Plumbing pipes through the roof | Rubber gasket cracks at 10-15 yrs — the #1 leak source |
| Skylight flashing | Perimeter of skylights (manufacturer kit) | Improvised site-bent metal instead of the kit |
The failures we actually find
The missing kick-out
Where a roof edge dies into a side wall above a gutter, a small kick-out flashing must throw the water into the gutter. Skip it, and years of runoff go straight behind the siding — we have opened walls in Kenmore and Kent with rotted sheathing traceable to this one missing $20 part.
Cracked vent boots
The rubber gasket around plumbing pipes lives a hard life in UV and rain. It cracks around year 10 to 15 — typically half the life of the roof around it — and drips quietly into the attic near a bathroom. A boot swap is a $150 to $350 repair when caught early.
Reused step flashing
The reroof shortcut: leaving old step flashing in place and caulking it instead of weaving new pieces with each shingle course. Caulk is a maintenance product, not a flashing system — it buys a couple of years, then leaks. An itemized quote should say new step and kick-out flashing. Our roof edge guide covers how drip edge and the panel edge work together.
Flashing repair costs
| Repair | Typical cost |
|---|---|
| Vent boot replacement | $150 to $350 |
| Step flashing rework (one wall) | $400 to $1,000 |
| Chimney flashing rebuild (base + counter) | $600 to $1,500 |
| Kick-out retrofit + siding patch | $300 to $900 |
| Valley re-flash | $500 to $1,200 |
FAQ
What is the most common flashing to fail?
The plumbing vent boot. Its rubber gasket cracks in 10 to 15 years — roughly half the life of the shingles around it — which is why a mid-life roof inspection almost always includes boot replacement.
Should flashing be replaced with a new roof?
Yes, with rare exceptions. New shingles woven against old step flashing is the classic reroof shortcut; the metal is already fatigued and the caulk sealing it is temporary. Ask for new step, kick-out, and drip edge on any full replacement quote.
What metal is roof flashing made of?
Most residential flashing is galvanized steel or aluminum; copper appears on premium work and around masonry chimneys where it outlasts everything else. In the Pacific Northwest, coated steel and aluminum handle the constant moisture well — bare galvanized eventually streaks and rusts.
Can flashing be repaired with caulk or roofing cement?
Only as a stopgap. Sealants shrink and crack within a couple of seasons. Proper flashing sheds water by lapped layers, not adhesion — if a bid proposes to fix a flashing leak with sealant alone, it is a temporary patch priced as a repair.
How do I know if a leak is flashing or shingles?
Location is the tell: leaks that show up near chimneys, walls, skylights, or bathroom vents are flashing until proven otherwise. Field-of-roof leaks away from any feature point to shingles or underlayment. An inspection with photos settles it.
Flashing done right, documented with photos
The Roofing Titan installs and repairs roofs across Kenmore, Kent, and Greater Seattle with the edge, flashing, and underlayment details built for Pacific Northwest weather. Request a free inspection with a photo report and get a straight answer on what your roof actually needs.