How to Install House Wrap around a Window


Proper flashing detail around a window

Proper flashing detail around a window

When I head out around the countryside, I am frequently dismayed by all the examples of improper construction techniques. “There’s another house that’s going to rot out in a few years” I think to myself.

So, when I saw this new construction, I did a double-take. Did the contractor actually properly install the house-wrap (Typar or Tyvek) around the window? Amazing!

Let’s look at what they did right:

  1. They used Typar house wrap which is generally a better product than Tyvek. But installed correctly, each can do a fine job
  2. They installed the house wrap horizontally in long, continuous segments. This reduces the number of seams, which are potential failure points.
  3. They used the Typar tape for the seams. This is a little detail that is often missed. The house wrap is slippery material and using the wrong tape on the seams can lead to failure. Only the factory approved brand should be used whether it be Tyvek or Typar.
  4. *IMPORTANT* They sliced the wrap above the window and installed the top piece over the window’s nailing flange. This directs water properly. 90% of the installations are done without this detail which leads to water getting under the nailing flange!
  5. *IMPORTANT* They taped the wrap under the nailing flange and over the bottom sill. Again, this is critical for proper drainage. If water gets behind the window, it drips onto water-impervious Grace Vycor then drains out at the bottom flange. Most installers tape the bottom flange to the house wrap which traps water inside the wall.

So kudos to the builder. This home is much less likely to rot out than 90% of the other new constructions!

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