Down and Out Is the Rule for Draining the Rain
I'm seeing more and more projects with house wrap where the installers do the window details properly. Or at least better. The photo below shows the house wrap lapping over the flashing tape at the top of the window. Often it's the reverse. And the house wrap in those cases is not only beneath the flashing tape, but it's also beneath the window's nailing fin.
So they did that detail pretty well here. Water that gets behind the cladding will run down the house wrap and not be channeled down into the framing if the tape fails or wasn't installed well. Likewise, water that gets behind the house wrap should be stopped by the tape, unless it fails.
But let's step back and take a look at the bigger picture for this house. The photo below shows that same window — and what's above it.
The first thing to note is that we have a design failure. There's a window right below that roof section. And there's also this thing called gravity, which still likes to pull things downward. Water hitting that roof could lead to failure at that window or on the wall unless all the details are done properly — and maintained.
See any potential problems at that roof wall intersection? Let's zoom in.
Hmmm. The house wrap runs down behind the step flashing. They made the mistake here that they avoided at the window header. Water that gets behind the cladding can get channeled down behind the step flashing. That's almost a certainty for water that gets behind the house wrap. (Here's a nice article on Fine Homebuilding's website showing how to install step flashing.)
In addition, there's no flashing behind the house wrap right below the bottom course of step flashing. Even if they came back and put tape all over that area, it's in the wrong place. Water could be coming down behind the tape.
Here's what the house looks like now that it's finished.
It may be a little hard to see in this photo, but there's no kickout flashing here. That's another detail that can help keep the water away from that wall as it comes down the roof when it's raining. (Here's a nice article on Fine Homebuilding's website showing how to install kickout flashing.)
I've written a lot about the importance of being a building enclosure control freak. Controlling the flows of heat, air, and moisture (both liquid and vapor) is critical to achieving comfort, healthfulness, durability, and energy efficiency. Of the four things to control, though, liquid water is the most important. It can cause a building to fail more quickly than any of the others.
Unfortunately, a lot of builders are still putting houses like this on the market. The kinds of problems I found in the one described here aren't rare. And home buyers who see only the final product have no way to know that there's a ticking time bomb built into their new home.
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