Dry-In: Windows - Day 1-3

With a project this size, you get the hang of a new building skill at just about the same time as you finish the job that required it. These past three days, that skill has been window installation.

The thing is, though, even the first window wasn't difficult to install, per se. We did it wrong, is all: we used too-short nails and forgot to create a gap for sealant along the bottom.

Two lessons learned. But the main one is Lesson 50: Communicate constantly with your work partner--don't assume they know exactly what you think should be happening at a given moment, and double-check that you are both following all the steps correctly. Just keep up a constant patter of checking and double checking and one of you, at least, should catch when you're going wrong!

On the second day of window installation, we got the two kitchen windows installed. Those are the vertically oriented single-hung windows on the tall side of the house. And we learned just how wrong you can go when you let that patter of checking and double-checking lapse...

We installed one of the windows inside out.

We'd been having a tough time up on the roof trying to get the sheathing square and ready for the fascia boards, so we decided to come down and install a couple windows. We were hot and frustrated and it would be more comfortable down on the ground. Besides, installing windows isn't so hard.

Uninstalling a window is considerably harder. Lesson 51: When you need a break, take an actual break!

Luckily, we only got halfway through the installation before I realized what we'd done; most of the nails were in, but at least we hadn't put the flashing tape over the nailing fins. (That stuff is almost impossible to remove; we'd have had to cut out the Tyvek there and reinstall it, too.) Dad drilled out the nails, I scrubbed the half-set silicone caulk off, and we reinstalled it right-side out.

On the third day of window installation, we finally had the hang of it. Four windows, zero foul-ups!

So how do you install a window? Here's how I did it:

Window hole cut in house wrap

1. After installing the house wrap, the first step was to cut a hole in it at the window opening. There are a couple ways to go about this, but I used the "upside down martini glass" method: cut a horizontal slit across the top, flush with the edge of the rough opening (base of the glass); cut a vertical slit down the middle, stopping 6-8" above the bottom of the opening (stem of the glass); and cut two diagonal slits from where the vertical cut ended to the bottom corners of the opening. This creates three flaps, which get folded into the window opening and stapled snugly out of the way.

Flashing on the bottom of the window opening.

2. I used Grace Vycor Plus self-adhesive window flashing tape for all my windows. Three pieces go on the bottom of the window opening. The first piece (width of opening + ~4") goes straight across the bottom of the opening, flush with the edge of the opening and extending a couple of inches beyond the corners on both sides. The next piece (...+12") is applied to the window sill so that it extends about 6" up the opening on each side. Half the width of this piece of tape hangs out of the window and is folded down, overlapping the previous piece. The corners are tough to fold down, **edit** which I later found is because it's not actually meant to stretch that much. Oops... Better to cut a slit to make it around the corner. (I had to use a reinforcing staple to keep it stuck down...) The final piece of tape (...+12") is applied to the window sill, flush with the inner edge of the opening and also extending 6" up each side.

Chiseling out the curved corners

3. Now, or before, is the time to cut two diagonal slits above the window, from about 4" above and outside of the upper corners down to the corners. I folded the flap of Tyvek up and taped it out of the way.

4. I also made sure to test-fit every window before committing. As it turns out, the curved corners of the SIP window openings did not allow the windows to comfortably fit, and if we forced them, the corners of the windows would rip the window flashing tape. We chiseled out those curved corners to give the window more room, and knocked off any drops of adhesive from the SIP installation that might get in the way. We also used a rasp to smooth the corners of the windows themselves, so they wouldn't catch and tear the flashing tape.

5. I applied a 3/8" bead of silicone window caulking around the top and sides of the window opening, where the window's nailing fins would lie. I did not apply caulking to the bottom; any water that gets in behind the window needs to be able to drain out.

Level and shims. Sadly, this was the inside-out window... :-(

6. One of us went inside the house and the other pushed the window into the opening until the nailing fins lay flush against the side of the house. (Making sure that the window was inside-in and upside-up!) While the outside person held the window in place, the inside person used a short level, tapered cedar shims, and a pry bar to lift the window up in its opening until two conditions were met: there was about an equal gap around all four sides of the window (about 1/8" to 1/4", so you can seal it up with spray foam); and the bottom of the window was level.

Nails hammered into the nailing fin

7. When the inside person was satisfied that the window was in the right place, the person on the outside hammered a 2" galvanized roofing nail into one bottom corner of the nailing fin. If the window was still level, they hammered a nail into the opposite corner. If it was still level (and pray that it was), then the top corners would be nailed in, then the rest of the nails hammered in, too. A pneumatic nailer was very helpful!

 8. Finally, the rest of the flashing tape went on.


First, two pieces of tape (...+8") along the window's sides that extended 3-4" above and below the window.

 Then, a piece of tape (...+8") straight across the top of the window, extending ~4"to either side and covering the ends of the previous two pieces of tape.

Finally, I folded that flap of Tyvek down and taped the diagonal slits with two pieces of tape that were a couple of inches longer than the slits (usually about 8").
















Ta da!

Later, when the door is installed, we'll go around with a can of low-expansion spray foam and fill in all those gaps around the windows from the inside. I think we can cut off the folded-in flaps of Tyvek now, too.

Can't even tell which one was the epic reinstallation struggle...

Bedroom window

I'm happy that my windows are in, and Dad's happy that my windows aren't in his shop anymore. It's a win!

We are still struggling with getting the roof ready for the fascia, verge rafters, and soffits. We need to install those things (well, mainly the fascia and verge rafters), the Ice and Water Shield roof membrane, and the door before the house will be officially dried in. There are rain showers forecast for Thursday, so we need to get a move on!