Types of Roof and Wall Flashing: A Contractor's Guide

Quick Answer: The Main Types of Flashing

The main types of roof flashing are step, counter, kickout, base, headwall (apron), valley, drip edge, and pipe or penetration flashing. On walls and siding the ones that matter are head flashing, sill pans, Z-flashing, kickouts, and through-wall flashing in masonry. Every one of them covers a spot where water wants in.

Step Flashing

Step flashing handles the spot where a sloped roof runs into a vertical wall, a dormer, a chimney, or the side of an addition. Instead of one long piece, it is a stack of small L-shaped pieces, each one stepped up the slope. The roofer sets a piece on top of each course of shingles before the next course goes down, so the flashing weaves right into the roof.

That layering is the whole reason step flashing holds up. There is no long continuous seam to split open down the road, just piece over piece, each one shedding water onto the one below. For steep-slope work we brake-form it in 5" × 7" pieces at minimum, but we cut the profile to whatever your detail calls for. Galvanized steel, aluminum, or copper.

Counter Flashing

Counter flashing caps the top of the step flashing where it meets the wall. The step flashing runs up alongside the roofing, and the counter flashing tucks into the wall above it and laps back down over the top, so water cannot sneak in behind.

Here is the part people miss. Counter flashing is supposed to leave a gap between the roof system and the wall system. The two move at different rates when things heat up and cool down, and that gap lets them. Lock them together and that movement pops fasteners and cracks your sealant in a season or two. On masonry, the counter flashing sets into reglets cut into the mortar joints and seals in there.

Kickout Flashing

Kickout flashing, some folks call it diverter flashing, sits at the very bottom of a step flashing run, where the wall keeps going down past the roof edge. Its one job is to throw the water that has been tracking down that roof-to-wall seam out into the gutter, instead of letting it dump in behind the siding.

Leave it off and you have a problem. Missing kickout is one of the top reasons water gets behind cladding, and it is brutal on fiber cement and stucco. The water hides behind the wall, rots the framing, grows mold, and runs up a repair bill that dwarfs what the flashing would have cost. This is one to fabricate custom, not pull off a shelf. We form it to the exact geometry of your roof edge, gutter, and fascia.

Base Flashing

Base flashing works the bottom of the vertical stuff on a roof, where a flat surface like a roof deck butts into a parapet, a chimney, a curb, or a mechanical unit. It carries the waterproofing up and over that horizontal-to-vertical turn so the seal never breaks.

On a flat roof, base flashing runs up the face of the parapet at least 8" above the finished roof, with the bottom worked into the roofing membrane. Up top, coping or counter flashing laps over it to finish the assembly. Pick your material with care here. It has to play nice with the membrane, take the heat that builds up at roof level, and outlast the roof it is protecting.

Headwall, Valley, Drip Edge and Pipe Flashing

Headwall flashing, also called apron or continuous flashing, is the long piece where the top of a sloped roof meets a wall. Because it is one long run, it needs room to move. A long continuous piece that is nailed tight to both the roof and the wall is a piece that buckles.

Valley flashing lines an open valley where two roof planes meet. Drip edge runs the eaves and rakes and gets water off the edge instead of letting it curl back under. Pipe flashing seals plumbing vents and other penetrations. Skylights often ship with their own flashing kit, but odd curbs still end up needing a custom piece.

Wall and Siding Flashing Types

If you hang siding or lay brick, this is the half of the job that roof guides skip. The roofer's flashing stops at the wall. Everything below that line is on you.

• Head flashing. Goes over the top of windows and doors. It laps out over the trim, so water running down the wall gets kicked out past the opening instead of into it.
• Sill pans (pan flashing). Go under windows and doors. The pan catches anything that gets past the unit and sends it back outside. Code lets pan flashing be premanufactured or formed for the job, so a shop-bent pan built to the rough opening is fair game.
• Z-flashing. The workhorse on panel siding and trim. It sits at a horizontal joint, tucks up behind the WRB and laps out over the piece below. James Hardie's panel instructions call for Z-flashing at all horizontal joints and a 1/4" gap above it that you do NOT caulk, so it can drain.
• Kickout flashing. Same part as on the roof, but it is really a wall detail. It sits where a roof dies into a sidewall and the wall keeps going down. Skip it and the whole roof-to-wall seam dumps behind your siding. Fiber cement, vinyl and brick veneer can hide that water for years.
• Through-wall flashing (masonry). Brick and block walls drain the cavity, not the face. Flashing goes at the base of the wall, over heads, under sills and at shelf angles, turned up into end dams at the ends, with weeps right above it. Weeps only work if the flashing actually sends water to them.
• Coping and cap flashing. Tops off parapets and wall caps. The code list calls for flashing under and at the ends of copings and sills. On parapets this is where a sloped coping with a drip overhang earns its keep.

We bend all of these for siding, stucco and masonry crews. See our siding trim and flashing work, stucco flashing, and door pans and saddles built to field dimensions. Got a detail? Send it over for a 24-hour quote.

Where Flashing Is Required

The residential code (IRC R703.4) lists where wall flashing has to go. Your local edition may word it a little differently, so check what your jurisdiction adopted, but the list looks like this:

• At the head and sides of exterior window and door openings
• Where chimneys or other masonry meet frame or stucco walls
• Under and at the ends of masonry, wood or metal copings and sills
• Continuously above projecting wood trim
• Where porches, decks or stairs attach to a wood-frame wall or floor
• At wall and roof intersections
• At built-in gutters

On the roof side, the code also calls for a flashing that diverts water away where the eave of a sloped roof meets a sidewall. That is the kickout. Step flashing at a sidewall is typically at least 4" up the wall and 4" out on the deck.

What Is the Best Material for Flashing?

There is no single best. It depends on what the flashing touches and how long it has to last.

Galvanized steel is the usual pick. It is strong, it bends clean, and the zinc coat fights rust. Aluminum is light and easy to form, but bare aluminum breaks down against concrete and masonry, so it needs a coating there. Copper outlasts both and is still common around chimneys, but it turns green over time.

Here is what we stock for flashing: prefinished or primed steel 20 to 26 gauge, G90 galvanized, aluminum 0.030" to 0.060", stainless 304 or 316, and 16 or 20 oz copper. Mill, prefinished and Kynar finishes. Pieces run up to 10 ft.

The Most Common Flashing Problems

• No kickout at the bottom of a roof-to-wall run. Water goes straight behind the cladding.
• Pieces lapped backwards. An underlapped piece pushes water INTO the wall instead of out.
• Flashing nailed to both the roof and the wall. When the building moves, the flashing tears or warps.
• Bare aluminum against concrete or masonry. It corrodes.
• Long one-piece runs with no way to expand. They buckle.
• Kickouts and diverters that are too small or have open seams, so they leak at the one spot they are supposed to protect.
• Caulking the gap above Z-flashing. That gap is how the joint drains.

Getting Flashing Made in Portland

Every profile on this page is something we brake-form in our Portland shop. Send a drawing, a sketch with dimensions, or a sample piece. No minimum order, most flashing ships in 3 to 5 days, and you get a quote in 24 hours. Start with our custom metal flashing fabrication page, or go straight to the quote form. Not sure what a gauge number means in inches? Check our sheet metal gauge chart.

Sources

• IKO: What Is Roof Flashing and How to Install It
• U.S. DOE Building America Solution Center (PNNL): Step and Kick-Out Flashing at Roof-Wall Intersections
• James Hardie: HardiePanel Vertical Siding Installation Instructions (Z-flashing at horizontal joints)
• International Residential Code R703.4 Flashing, as adopted in Minnesota Rule 1309.0703
• Journal of Light Construction: Kickout Flashing, Required by Code, Yet Often Overlooked
• Masonry Advisory Council: Flashing, Tying the Loose Ends

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