The bearing walls are structural insulated
panels made with galvanized steel frames encapsulated in expanded polystyrene.
The steel stud faces are on both inner and outer surfaces but
they do not pass through the thickness of the panel. Therefore no
steel thermal bridges pass from inside to outside.
Each 4' x 9' panel weighs about 80 pounds. They are pretty
awkward to carry, but I built a little sling that made it much easier.
After the steel channel plate is fastened to
the slab, the panels are tilted up in place and seated in the channel
plate. They have shiplap edges with overlapping steel flanges so
they can be screwed together. Add a little bracing and move on to
the next one. I learned early on to find some other activity on
windy days.
The top plate is actually a 2-piece box
section. I ran the telecom, security, and datacom wiring inside the
box before placing the upper cover. The cabling is fastened near the
center for protection from screws that will later be driven from the
sides.
The power wiring runs in conduit I placed before the slab was
poured. The conduits rise at pre-planned spots in the wall
centers. I wanted no wiring runs through the attic except as needed
to reach light fixtures.
I was getting pretty discouraged by winter
'96. It was taking so long to get the walls and wiring in place, and
almost every morning I had to sweep the rainwater off the work area before
starting. Looking back now I had no concept of how much worse things
would get before they started improving.
But finally the bearing walls were up and
plumb, and the concealed wiring was all in place. Only the top plate
box section had to be finished and I could start on the roof.
Eventually, after the roof load was in place
for a while, I added the shear X-bracing straps to the walls. Houses
here need this to survive earthquakes.
The X-braces are first tensioned and then
fastened like this. It may seem like overkill, but it is what the
engineering calculations call for. The straps and gusset plates are
16 gauge steel. The hold down straps are 11 gauge.
