Tips for Installing Leakproof Kickout Flashing

Poorly installed or missing flashing at roof-wall connections is a common cause of water damage. Here's the solution

August 22, 2016
Kickout flashing replaces the first piece on step flashing and redirects water away from the siding (ideally into a gutter). Without a kickout, water will eventually get behind the siding and into the wall, where it will wreak havoc for years before you notice any signs of a leak.

Kickout flashing replaces the first piece on step flashing and redirects water away from the siding (ideally into a gutter). Without a kickout, water will eventually get behind the siding and into the wall, where it will wreak havoc for years before you notice any signs of a leak. All illustrations: Dan Morrison

Ground zero for roof rot is often where roofs meet walls. If water isn’t redirected from the roof into a gutter, it can pour into the wall, where over time it will rot the sheathing and framing and wreak havoc with insulation and drywall. The solution is kickout flashing, which replaces the bottommost piece of step flashing and directs water away from the wall and into the gutter. 

Some contractors make their own kickout flashing from a standard piece of step flashing by cutting the roof leg in half, then sliding the upper half over the lower half. But unless this joint is soldered, it will eventually leak, defeating its purpose. 

Another option is to use a prefabricated kickout flashing, which is available in powder-coated metal ( or plastic ( for less than $20. In a pinch, you can make your own by crimping the roof leg rather than cutting it (see “DIY Kickout Flashing.”).

Here are step-by-step instructions for prepping the roof and wall for kickout flashing, adapted from the “Best Practices Manual” of high-performance builder/remodeler Hammer & Hand, in the Pacific Northwest. (The manual is available at

Step 1: Waterproof the wall.

Apply waterproofing membrane where the bottom of the roof meets the wall [1]. In new construction, apply a peel-and-stick membrane directly to the wall sheathing before fastening a rafter to the wall. As an alternative—especially for retrofit work where roof framing and fascia is already in place—use a liquid-applied paint-on membrane such a FastFlash. The waterproofed area should cover the wall at least 4 inches in all directions from the framing, including the area below the fascia. 

Be sure to integrate this membrane into the existing housewrap using proper overlaps. If necessary, make the transition to housewrap at the bottom of the waterproofing with flashing tape, which can be lapped over and sealed to the housewrap later. Extend the flashing tape at least 10 inches past the fascia.

Step 1: Waterproof the wall.

Step 2: Flash the roof and roof-wall connection.

Next, install a course of peel-and-stick membrane along the eaves, folding over the bottom 2 inches onto the fascia [2]. After installing metal drip edge, run a strip of peel-and-stick membrane to cover the entire joint where the roof meets the wall, extending the membrane about 8 inches onto the roof and up the wall.

Step 2: Flash the roof and roof-wall connection.

Step 3: Install the kickout flashing.

Install roofing felt or synthetic roofing underlayment over the roof, running it up the wall at least as high as where the top of the step flashing will be [3]. Next, install a starter strip of roofing, then use the kickout flashing in place of the first piece of step flashing. Make sure it overhangs the eaves far enough to direct water away from the roof and wall and into the gutter. 

Step 3: Install the kickout flashing.

Step 4: Weave in the step flashing.

Install step flashing and roofing, alternating as necessary to ensure that each piece of step flashing overlaps the lower piece by at least 2 inches [4]. The top of standard step flashing should align with the top of the shingle, but the overlap is the important thing, as is ensuring that the step flashing doesn’t peek out from underneath the shingles. 

Step 4: Weave in the step flashing.

Step 5: Flash the step flashing.

After the roofing and step flashing is complete for the entire length of the roof-wall connection, add another strip of peel-and-stick membrane over the top of the step flashing, cutting a slit for the kickout flashing and leaving a 2-inch gap between the membrane and the roofing [5]

Step 5: Flash the step flashing.

Step 6: Button up the housewrap.

Install housewrap on the wall from the bottom up [6]. Use flashing tape along the bottom of the waterproofed wall area to ensure continuous drainage, being careful to lap the upper courses of housewrap over the lower ones and making a slit for the kickout flashing. Keep the housewrap as well as any type of siding material about 2 inches off the roofing. 

Step 6: Button up the housewrap.


About the Author

Sal Alfano is Director of Content for Professional Remodeler.
Adapted with permission from the “Best Practices Manual” of Hammer & Hand, a Portland, Ore., and Seattle-based general contractor specializing in high-performance buildings.

About the Author

Dan Morrison is senior technical editor of, a sister site to Professional Remodeler.



I need this done to my stone fireplace and am researching because I can't find anyone to fix my fireplace leak. I am a 79 year old woman in N. E. Arkansas and sure don't know what to do. An adjuster mentioned this shown above and I am just trying to educate myself a bit. Thanks for the great explanation, but I am too old to get up on a ladder and do the work myself. LOL

The Detail and description look simple enough. The question I have is how do you accomplish this with the exterior finish is 3/8" T 1-11 Siding where the wall extends beyond the overhang? The T 1-11 serves as the shear as well as the finish exterior.

The point of flashing is to direct liquid water out and away from the building. It should be overlapped single-style behind the WRB, which is usually house wrap.

Kickout flashing is no different. Really, it is just a modified step flashing, so however you are detailing the step flashing behind the T1-11, would be a good place to start.
One way to do that is to leave the T1-11 off until the roof is flashed into the wall. But that will make it difficult or impossible to replace the step flashing when the roof is replaced, so use a very durable step flashing material.

Your question brings up a bigger issue: how to flash ANYTHING into an assembly with T1-11: head flashing over windows and doors, ledger flashing at decks, even simple horizontal roof-to-wall flashing where a shed roof abutts a wall. If you cut the T1-11 to slip flashing behind, you've created a huge air leak that now must be sealed (2 huge air leaks, actually -- one above the flashing and one below).

Theoretically, you could treat it like masonry and use a counterflashing inserted into a saw kerf to cover the vertical leg of the kickout and step flashings, but with 3/8-thick material, that's going to be really difficult to do that well.

Usually, those connections rely on a tube of caulk for water protection, and that's not a very good long-term strategy.

If you Google search flashing details for T1-11, a LOT of the results are about replacing rotted T1-11, which illustrates the high cost of cheap construction. Bad flashing causes buildings to rot. Claddings which do not allow easy flashing installation are more prone to rotting prematurely, which means an EXPENSIVE repair, and possibly, a structural catastrophe.

Can you show flashing with standing seam with vinyl siding and j channel.

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