Dormer Leaks for Dummies

Dormer flashing

Those among us who live in houses where we perform our own maintenance – as opposed to living in a dorm, condo, or an apartment – know water as the arch-enemy. Water doesn't just come from nearby rivers in flood season, though; sometimes it comes through the roof. The sad fact is that anywhere that there's any sort of penetration of the roof is prone to leak, and dormers are just one of many such culprits. The seriousness of those roof leaks, however, is why we're featuring eHowian Jess Kroll today, based on his HomeSteady.com post, "How to Stop a Dormer Leak."

It's almost totally certain that our young "creative writing" graduate, poet, and film reviewer had never worked on a roofing crew; and that he had probably never even been on a roof (unless it was a rooftop nightclub). Truth be told, it's highly possible he had no earthly idea what dormers are before he claimed this particular title! Kroll opened by explaining that,

"Dormer roofs are often made of a cheaper, less durable substance than the rest of the roof. Most dormer leaks occur as the flashing deteriorates and the connection between the two roofs is weakened..." In all honesty, we have no idea where Jess came up with the notion of a "cheaper, less durable substance"; or decided that a leak happens because a "connection between the two roofs is weakened." It's pretty clear that he learned somewhere that the most likely cause of a leak around a dormer is bad flashing, but it looks as though Kroll just wasn't quite certain what this "flashing" stuff is. After all, he tried to explain that, "If the flashing has rusted... it must be replaced."

Wait, what? Flashing does not rust, Jess, because it isn't made of ordinary steel: these days it's sheet aluminum, but might also be lead, copper, or even stainless steel. No rust there, Jess! More dumbassery ensued, however, as Jess attempted to explain how to replace flashing – and here we point out that it's often easier to replace flashing when the entire roof is done than it is to replace a bad section. Anyway, here's some of what Kroll thought should be done:

• "Remove the old flashing and pull it away from the dormer and the shingles."
• "Push [replacement flashing] to fit flush under the folded shingles and all the way around the dormer"
• "Apply caulking to seal the edge of the dormer and each shingle..."

It's pretty obvious that Jess wasn't aware that the flashing folds in the valley and extends under the siding of the dormer. He was also blind to the fact that the flashing may have been "stepped," and that any and all points at which there's a joint flashing, the overlap must prevent water from running underneath the flashing. He also confuses caulk with roofing cement, which allows for greater "stretch" with seasonal changes in temperature.

In other words, any poor schmucks who think they're getting useful advice from our Dumbass of the Day about how to install or replace flashing are sadly mistaken. We suggest that they consult a pro instead...

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