Dry-In: Weatherproof Barriers - Day 2

The walls are (almost) completely wrapped and taped! And I'll tell you, I am glad to see the back end of this stage of construction. See: my previous comments about the infuriating nature of Tyvek...

As you can see in the photo, I've chosen to extend the house wrap all the way up between the rafters, nearly to the sheathing. The roof overhang will be so short that I wanted the extra protection there. Aside from that, the coverage is pretty much typical--that is, total coverage, even over the window and door openings. (More about those in a moment...)

Install house wrap from the bottom up!

The most important thing to remember is to install the house wrap from the bottom up. The house wrap higher on the wall needs to overlap the lower courses (rows) so that water can't flow down and underneath. Always give water a path out and away from sensitive materials like sheathing.

The second most important thing is to overlap the Tyvek at least 6" wherever there is a transition between pieces.

You can install Tyvek upside down or sideways, but not inside out. Apparently? Some people on the internet claim there is no difference between how Tyvek performs from inside out versus outside in; others say that water will soak in if you install it with the logo side facing inward. A simple experiment could determine who is right! 

The lower courses are easy to do just by rolling the house wrap out along the wall. We left about a foot below the bottom of the wall, just to be sure we'd have plenty of coverage there. I cut off the strip of extra later and used pieces of it between the rafters.

As we applied the Tyvek to the wall, we stapled it in place. Cap nails, with wide plastic heads, are the recommended fastener--they keep the house wrap from pulling free better than staples do. Staples worked okay for us, but if we'd had a cap nailer and cap nails, we would have used them for sure.

After the wrap was up, we taped all the seams with the special super-sticky tape designed for the job. We needed at least two full 164' rolls of Tyvek tape (we used the 2" wide version). We had a partial roll given to us by our builder friend, Jim, and a whole roll, and then I did the last few feet and dibs and dabs with a roll of cheaper store-brand stuff that was left over from the subfloor bays.

Window openings cut, folded back, and secured

What we noticed as we installed the Tyvek is its sail-like nature. The breeze catches it like crazy! After the taping, we cut slits at the window openings to equalize the air pressure so that a faint puff of wind wouldn't blow the Tyvek off the whole house.

Believe it or not, there is a special way to cut those slits for the windows. It's an "upside-down martini glass": the base of the glass is a slice straight across the top, flush with the edge of the window opening. The stem of the glass is a vertical cut down the middle of the window opening, to about 8" from the bottom. The bowl of the glass is two diagonal cuts from the bottom corners up to the point where the stem cut ended. Then fold the three flaps around the inside of the window and staple them to secure them (otherwise they'll flutter noisily in each slightest breeze).

Window opening prepared for flashing and window installation

When you prepare to put a window in, you cut two more diagonal slices that start about 4" above and outside of the window down to the upper corners. That flap gets folded up and out of the way and pinned with a little piece of tape. At this point, the window is ready to receive window flashing and then (ratatatatata) the window!

The windows and the roof's weatherproof membrane are the next two phases of the so-called dry-in stage of construction, as well as the door. More on all that soon.