Walls - Day 5-7 - The Fourth Wall

There it is, everybody. The fourth wall is up (thanks to our neighbor Leif for helping with the big lift!), the window rough openings are all framed in, and we are ready for the top plates. Back to that in a minute...

Yesterday (Day 6:) we mostly spent puzzling over electrical wiring. I had planned to have a very simple wiring schematic, with no complicated three-way switches or anything like that... but then (with Dad's help) I realized two things:


First, it would be really nice to be able to operate my main room light from bed as well as from the door, and to operate my loft light from the door as well as from the loft. Adding that capability means adding two sets of three-way switches. (I drew the line at being able to operate the exterior light from my bed. Might be nice if I were in bed and heard someone or something rooting around outside my house and wanted to scare them off, but it's on a whole 'nother circuit and that's starting to be a lot of wires to run from a single bedside switch box...)

Second, it's not going to be workable to have my main set of light switches to the right of the door as you walk in, as I'd planned, since the hinges will be on that side. I didn't think it through. I need to put those switches on the other side, where the cabinets will be. I think it will work, though: although there isn't a chase inside the wall there, there will be a cabinet, so it will be easy to conceal a surface-mounted chase behind the cabinet and have the switch box concealed by a ledge on the side of the cabinet. I was already planning to have a ledge there as a "drop spot" for keys, sunglasses, and the like.

Thursday (Day 5:) I had a training session to start to learn to identify zooplankton through a microscope at the Padilla Bay National Estuarine Research Reserve. Yay, labwork! Yay, science!

Window opening with framing installed

Then I came home and finished framing the last of the window rough openings. Like the panel edges, the window cutouts have an (approximately...) 1.5"-deep groove of foam recessed from the edges, allowing regular 2x lumber to fit (approximately...) flush with the edges of the OSB when installed inside the groove. These cutouts need to be lined with 2x4 lumber to fill those gaps, protect the OSB, and--most importantly--provide a solid substrate on which to install the windows.

The foam isn't always recessed evenly...

... and things might not fit exactly.

Most, if not all, SIPs are cut using what's called a CNC (computerized numerical control) machine. You feed the dimensions to the machine digitally and it makes the cuts exactly according to those numbers. Then the foam is scooped out by hand, using a hot knife, 1.5" from the edges that the CNC machine cut. For my panels, the window cutouts had rounded corners, not straight 90º corners, which meant that the grooves in the foam also had rounded corners. Lumber, however, does not have rounded corners. That meant that sometimes it looked like the lumber pieces I'd cut were too short, because they were sitting up on a curved part of the foam. Sometimes I went in with a rasp and cut the curved corner down; sometimes I just piped some extra mastic in the corner and hoped everything would settle into place as the rest of the pieces went in. It seemed to work either way.

Eventually I discovered the perfect sequence to make window framing installation in SIPs easy. 

Lesson 46: Install the window framing in the following order:
1) Cut all the lengths of lumber to frame the window. The length of the top and bottom pieces should equal width of the window opening plus 3", and the length of the side pieces should be exactly the height of the window opening.
2) Take a piece of scrap 2x lumber and run it along the groove in the foam to make sure it's deep enough all around the window opening. If the foam wasn't removed to the full 1.5" depth at any point, use a knife, chisel, or rasp to excavate a bit. Remove those loose pellets of foam and any other debris before moving on to the next step (a vacuum works well).
3) Apply all the required beads (i.e. lines) of mastic/adhesive on all four sides of the window.
4) Install all four lumber pieces one after the other: first the top and bottom, then the side pieces. Use the side pieces to wedge the top and bottom pieces into exactly the right place, since they might not want to fit flush. Use a hammer to knock the side pieces into position. It will be tight; don't be afraid to use some force, but be careful to only hit the lumber, not the edge of the OSB.
5) Nail or screw through the OSB into the lumber all around the perimeter of the window, on both sides, according to the SIP manufacturer's instructions. (Mine specified 6" on-center spacing.) Make sure the fasteners penetrate the lumber about in the middle of the lumber, or 3/4" from the edge of the window, and make sure you don't sink a fastener too close to the end of a piece of lumber (I tried to stay back about an inch).

PS: high windows are easier to frame before installation.

Today (Day 7:) was the big heavy lifting day. Today we wanted to install the last panel, the fourth wall of the house. This last wall was also among the biggest: a full 8' across and 11' tall on one side, 9' on the other. That's 80 square feet of SIP, at about 4 pounds per square foot--you do the math--and no window to use as a handhold. Plus I had drunk a big mug of coffee this morning in addition to my normal strong tea and was feeling jittery, nervewracked, and a bit sick with overcaffennation. Bad choices.

I wasn't sure how we were going to make it, just the four of us, until Mom worked her magic--her not-being-pathologically-shy magic--and knocked on our neighbor Leif's door to ask for his help. Having a second strong person really helped!

Lesson 47: If I could order my SIPs over again, I probably would have asked them to include as many small (4' wide) panels as possible. Although I'm happy with the level of airtightness and lower number of seams involved with the large panels, the small ones proved so much easier to handle with a small crew (2-3 people). The end pieces, being shear walls, would probably have to stay the full 8' across, but any reduction in the number of big panels is a reduction in the chances of injuring yourself, a helper, or a panel.

Lesson 48: I bought some of the mastic/adhesive goop that Matt from Premier SIPs recommended as an alternative to the specially-formulated SIPs mastic. It's Loctite brand PL Premium polyurethane construction adhesive. It sucks. It stinks, it's heavy, it's hard to gun, the tubes leak, and it cures brittle. I'd much rather have ordered the nice, feather-light, non-VOC, rubbery-curing Premier SIPs mastic, which doesn't even cost more on a per-bottle basis. I suppose I still could, but we're so close to being done with needing it, and I'd have to wait for delivery and (I think) buy a whole case...

Oh well. Supposedly the stuff works, since it's approved by the SIP manufacturer, and that's mainly what matters. 

I'm also rethinking that roof overhang I talked about earlier... and thinking of using 2x8s instead of 2x6s, to get extra insulation space.

So much to think about!

I'll have to sit and ponder in my doorway from here on out.