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Bearing Walls


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.