If you would like to know more about the brand new state-of-the-art seismic retrofit guideline, there are around 30 educational videos and web pages that you will find interesting. Just type ICC 1300 in the search box in the upper right.
This is Detail 4, Sheet D1 as found in FEMA P-1100 Vulnerability Based Seismic Assessment and Retrofit of One and Two-Family Dwellings. It illustrates an upper block nailed to the foundation sill, or perhaps another lower block if the foundation sill is embedded in concrete. The plywood is attached to the block. The foundation sill is in turn attached to the foundation with a Simpson Strong-Tie URFP (Type A Connector).
The screws in the Simpson Strong-Tie URFP go into the mudsill and the plywood is nailed to the block even though they could both be attached to the foundation sill (also called the mudsill).
This Detail is from Standard Plan A.
In this case, the plywood is nailed to the sill and the Simpson Strong-Tie URFP screws penetrate the plywood.
As we just saw, the seismic retrofit guideline Vulnerability Based Seismic Assessment and Retrofit of One and Two-Story Dwellings requires blocking on top of the sill for the plywood, and then the URFP attached separately to the foundation sill. The concern is that the combination of lag screws every 3 inches with the 8d nails every 4 inches might cause splitting.
Below you see a 2 x 4 with nails every 1 inch between lag screws every 1 1/2″ with no splitting. I leave it to you to decide whether or not splitting is a problem.
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