Step 10:

Securing upper floors

Some building codes may require that upper floor membranes (plywood sheet floor) be secured to the foundations, particularly in multi-storey wood structures. This may be done with a threaded steel rod passed through the ceiling to secure the membrane, connected to anchor bolts in the foundation.

If this is not explicitly required, e.g. in 2-storey construction, it may nevertheless be desirable to secure the membrane by means of the wooden studs. Where an anchor bolt and bracket is fastened to the lower end of a stud, another bracket may be fastened to the upper end and a threaded rod passed through the ceiling joist to secure the membrane with a nut and washer, or metal plate.
Drill a clearance hole using an auger bit to pass the threaded rod.
I highly recommend that anyone attempting to implement this type of retrofit consult with a local engineer before proceeding. Building code requirements will vary with your locality. The design of seismic and wind load resisting systems for residential construction is a fairly complicated topic. The proper design of anchor bolts embedded in concrete is also a complicated topic. <br><br>Some additional comments:<br><br>Step 3: Note that the plywood sheathing carries most of the lateral load, not the stud to bottom plate connection. Reinforcing the stud to bottom plate connection for shear is not really necessary.<br><br>Step 4: The type of bracket you show in the photo is designed to resist an uplift force, not a horizontal shear force. The manufacturer representatives with Simpson Strong Tie and/or USP can assist you in selecting appropriate connector products for a given application.<br><br>When using epoxy anchors, you want to use products that are tested and approved for this purpose. The major manufacturers of these products include Hilti, Simpson Strong Tie, Epcon, and Powers. Again, I recommend talking to the manufacturer's representatives to select appropriate products. The strength of adhesive anchors can vary greatly depending on the type of epoxy, anchor diameter, spacing between anchors, proximity of the anchor to the free edge of the concrete, depth of embedment, and strength of the concrete.<br><br>Step 9: When replacing the plywood sheathing, I would recommend installing 2x4 blocking behind the plywood between the studs. The blocking would be set with the wide face vertical. The existing sheathing above and new sheathing below can then be continuously nailed to the blocking. Size and spacing of nails should meet local code requirements.<br><br>Although you can buy those nailing plates at home centers, they are not load rated for retrofit applications. They are commonly used in factory built truss fabrication, but in this case they are installed under controlled conditions with special presses. Simpson Strong Tie and USP make load rated connectors for this type of application, but you will need to talk to them to select an appropriate product. <br><br>Step 10: The angle bracket shown is probably not a good choice for this application. Again, the manufacturer's reps should be consulted for appropriate product choice.
This is a great instructable for an experienced do-it-yourselfer! And it doesn't just apply to the West Coast -- as several recent news items remind us, there are epicontinental earthquakes which can affect the midwest and east coast as well.

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