House wrap installation tips
House wrap installation is harder than you might think. Even veteran builders get it wrong, which is a shame, because all it takes is attention to detail.
Essentially, house wrap is a home’s first line of defense against air infiltration. In addition, it is a crucial layer for protection against moisture damage.
Why use house wrap? Consider these top three reasons:
- It sheds bulk water that has penetrated through the façade.
- It allows water vapor to pass through so the wall can dry out.
- It retards airflow for added energy efficiency.
Many builders believe humidity problems in a house are caused by water vapor being wicked through a wall (diffusion). In reality, far more moisture enters through small holes in the building envelope.
Think of house wrap as the hull of a boat. If there are holes in it, the boat is going to leak. Lots of little holes (commonplace in construction conditions) lead to big problems.
Mold, mildew, rotting window jams, drafts, and higher energy bills can result if house wrap is torn or improperly sealed during installation. Thankfully, these problems can be avoided by taking a little extra time and care.
Common house wrap installation mistakes
Mistake 1: Starting the house wrap in the middle of the sill plate or not covering it at all.
The bottom edge of the house wrap should fully cover the edge of the sill plate and overlap the foundation by at least 1 inch.
Mistake 2: Tear out a hole for the windows and be done with it.
At each rough window and door opening, make an inverted Y cut (also called a modified I cut) in the house wrap. Then pull each of the flaps to the inside of the opening and fasten to the inside face of the framing. You should be able to see the house wrap inside the window and door frames.
Mistake 3: Any fasteners will do.
Use the proper fasteners. Plastic cap nails are best. Some house wrap manufacturers allow staples with a minimum 1-inch crown, but staples don’t create the same airtight seal.
Mistake 4: What they can’t see won’t hurt them.
Before you put the siding on, repair all rips, tears and holes in the housewrap. Repair small holes or tears with code-approved contractor sheathing tape.
Patch larger gaps with housewrap (use a 6-inch overlap and install like a shingle), then tape.
Look at the two tears above the window. This installer saw the top tear and tried to staple it together.
Tape the tears and the horizontal seam; use plastic cap nails.
Mistake 6: A housewrap seam flapping in the wind, with a 2-inch overlap.
The top roll should overlap the bottom by 6 inches, and the seam should be taped to make a weather-tight bond.
Mistake 7: Housewrap doesn’t reach jamb on door opening.
House wrap wrapped around the inside of the rough opening, so it’s visible on the inside.
Mistake 8: The housewrap gets within 2 inches of the top of the wall.
The house wrap should wrap up and over the top plate.
–By Asa Foss, for the PATH Partners