Our 1951 house has 2x4" sill plates atop of concrete. We are in seismic zone D.
How frequently should the sill plate be bolted to the concrete?
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Depends on the load (weight and height above sill) acting parallel to the wall and sill plate.
We’ve learned that a load on the wall will just unzip it from the sill plate as the load gets transferred along the wall without a shear anchor bolt to stop the load in the first foot or so. That is to say that a bolt installed in the first foot of the wall will stop the load from traveling along the wall and just unzipping the wall from the sill plate.
Remember, the holddown must be installed in a 8” thick footing wall for it to be effective.
Generally in Zone D a 5/8” dia. x 24” deep rod with hook will be acceptable in a one story building with a roof that transfers the load to the sill using solid sheathing and nailed at 6” oc staggered.
I’d use something like this at each corner both ways:
Also, I’d use a 5/8” x 10” anchor bolt with hook at 24” oc along the wall and nail the sheathing 4” oc into sill.
Lee Sam
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