Kickout Flashing: How to Flash Troublesome Roof-to-Wall Intersections
Mike Guertin demonstrates how he uses redundant layers of flashing and kickout flashing to prevent roof water from slipping behind the gutter, causing damage.
The exterior of a house presents plenty of opportunity for leaks. A common problem area is the point where a gutter dies into an adjoining wall, as the photo below illustrates. Unless you’re careful, step flashing can allow water from the roof to slip behind the gutter and get behind the siding and even the housewrap.
A key part of my approach is using a special piece of flashing at this vulnerable intersection called kickout flashing or kickout diverter. They are available in several colors and in both plastic and metal. This simple but important precaution is required by the International Residential Code.
I use redundant layers of flashing integrated into the housewrap to keep water from getting behind exterior cladding. Kickout flashing directs water into the gutter. The process might seem overcomplicated at first, but the minor expense in time is much better than having to tackle rot repairs down the road.
1. Housewrap creates the foundation. Ideally, I like to start by installing a 3-ft. by 3-ft. sheet of housewrap (or even better, a piece of self-adhering roof underlayment) to the wall before the first truss or roof rafter is placed against it. The sheet acts as a backup at a vulnerable junction. When I can’t place the sheet ahead of time, I sometimes can sneak a piece of housewrap in after prying the truss or rafter back just 1⁄16 in. and pulling any nails that might be in the way.
2. If I can’t get some sort of weather barrier against the wall at the end of the eave, I apply a piece of housewrap that runs vertically from just below the soffit to at least 3 ft. down the wall, 6 in. horizontally around the inside corner, and at least a foot beyond the end of the eave.
3. Flexible flashing tape seals the eave to the wall. I use a wide piece of flexible flashing tape to protect the area between the subfascia and the wall. I cut the tape so that it laps onto the housewrap above and 3 in. above the roof sheathing.
4. Once the flexible flashing is set, I apply a piece of housewrap along the wall where the fascia meets it. This piece isn’t absolutely necessary. But later, it becomes easier to cover the wall completely with a final sheet of housewrap.
5/6. Protect the flashing tape. Although flexible flashing tape is pretty durable, it’s best to protect it with metal flashing and to treat it as a backup for water leaks. I fold a piece of metal flashing for the inside corner between the subfascia and the wall. A vertical cut about 2 in. to 3 in. long helps it to fold onto the roof sheathing. I then add a second piece of flexible flashing tape to cover the open corner of the metal flashing, and I fold it down onto the subfascia.
7. There’s optional backup protection, too. I build in 110-mph to 120-mph hurricane zones, so if I install a membrane beneath the step flashing and underlayment, it’s cheap insurance against a catastrophic event. I run a 12-in.- or 18-in.-wide strip of plastic-surfaced membrane from eave edge to ridge.
Trick of the Trade: The first piece of flashing should be a kickout diverter
8. After lapping the first piece of roof underlayment up onto the wall by about a foot, I install a kickout diverter flashing that redirects water into the gutter so that it won’t channel behind the siding.
The model I’m using is made by DryFlekt (www.dryflekt.com); it costs about $11 and is available in right- or left-hand models in white, ivory, or brown plastic. (Prefabricated copper versions are on the market, too, and cost about three times as much.) I line up the inside corner of the diverter 1⁄2 in. to 3/4 in. lower than the edge of the drip edge-essentially equal to the distance you overhang the first course of shingles.
9. Bigger step flashing is better. I recommend 12-in.-wide step flashings bent for a 5-in. roof leg and a 7-in. wall leg. The narrower step flashing just isn’t wide enough to protect the intersection fully.
10. Finish with tape. Finally, the housewrap can be laid up on the wall to cover the top of the kickout diverter and step flashings. I cut the wrap at the turnout in the diverter and seal the top of the cut with housewrap tape. The tape adhesive might not last the life of the cladding, but it’s a good precaution. Remember that there’s a layer of housewrap underneath that will keep the water from getting to the sheathing.
Watch the video:
Direct Water Into Gutters with a Kickout Flashing Diverter
-Contributing editor Mike Guertin is a remodeling contractor and consultant in East Greenwich, R.I. His Web site is www.mikeguertin.com.
More on flashing:
Installing Step Flashing to Prevent Roof Leaks – Step flashing spans the joint between roof shingles and an adjacent side wall. Here’s how to install it correctly.
Vent Flashing Done Right – To prevent leaks, back up roof vent boots with flashing, counterflashing, and proper shingling. EPDM flashing tape with a butyl adhesive backing will help.
Waterproof Your Windows With Liquid Flashing – Learn how to install liquid-applied flashing to seal the rough opening while leaving a path for water to escape.
Flashing for Old Windows – Old windows don’t have an integral flange, so getting a weathertight seal calls for some special techniques. Mike Guertin explains how.
Window Head Trim and Drip Cap – Here’s one approach to detailing the head of a window to direct water safely away.
Rain Diverter Protects an Uncovered Exterior Entryway – A simple metal strip fastened under asphalt shingles diverts rainwater toward a gutter.