What is kickout flashing and why does Calgary siding need it?

Kickout flashing is a small L-shaped or angled piece of metal installed where a sloped roof meets a vertical wall, specifically at the lower end of a step-flashing run where the roof edge terminates into siding. Its job is to redirect water that runs down the roof slope away from the wall and into the eavestrough, rather than letting it travel behind the siding. Without it, every rainstorm sends a sheet of water straight into the gap between the bottom course of step flashing and the siding, where it soaks the wall sheathing, the framing and eventually the interior.

Why Calgary's climate makes this especially important

Calgary's roughly 128 freeze-thaw cycles a year turn a small moisture intrusion into a serious one fast. Water that seeps behind siding in the afternoon freezes overnight, expanding and forcing the gap wider. Over a few seasons, the sheathing rots, the framing softens and mould follows. Chinooks accelerate the cycle: a warm wind melts snow on the roof in hours, sending a heavy flow of water down the slope right at that vulnerable termination point. Hail can also dent or displace the bottom course of step flashing, which makes a missing kickout flashing even more damaging because the path for water to enter the wall is wider.

The damage is insidious because it hides behind the siding for years. By the time a stain appears on an interior wall or a homeowner notices soft drywall near a window below a roof-wall junction, the repair bill often runs well beyond the flashing itself. Water intrusion behind siding at a roof termination is one of the more common causes of rot damage found during a full roof replacement in Calgary.

A kickout flashing costs almost nothing to install during a re-roof and a great deal to omit. Roofers should install one at every location where a sloped roof meets a wall and the roof edge runs into an eavestrough or simply terminates. If a quote does not mention kickout flashing at those locations, ask about it specifically before signing.

When you are getting quotes for a roof replacement or a repair involving step flashing, confirm the following in writing: that kickout flashing will be installed at every roof-wall termination, what material it is made from (aluminium or galvanised steel are common; avoid thin plastic in Calgary's temperature swings), and whether the siding will be carefully lifted and re-sealed around it rather than just caulked over. Caulk alone is not a substitute for properly integrated flashing; it cracks in cold weather and fails within a few years.

This is also worth checking on an older Calgary home where the original roofer may have simply bent the last piece of step flashing outward rather than installing a purpose-made kickout. That improvised approach rarely sheds water cleanly. If you are having siding replaced at the same time as a re-roof, the two trades need to coordinate the flashing sequence, because the kickout has to be integrated with both the roofing underlayment and the siding's weather-resistive barrier.

No building permit is needed from the City of Calgary for like-for-like re-roofing with no structural change, so adding or replacing kickout flashing as part of a shingle replacement does not trigger a permit on its own. If the wall sheathing behind the siding turns out to be rotted and needs structural repair, that is a different conversation.