I have a mud sill that was embedded in my home's foundation at time of pouring. Meaning, the top of the mud sill is flush with the top of the foundation wall. (More commonly, the bottom of a mud sill is flush with the top of the foundation wall.) Further, the mud sill is positioned on the outside edge of the foundation, making the inside edge of the sill concealed behind at least 2 inches of concrete.
For some more detailed context, see my previous question, which wasn't quite focused enough.
In my jurisdiction, seismic retrofit is typically required to pass remodel inspections, and I have an open remodel permit. We are on the 2021 iteration of the International Building Code (IBC), or International Existing Building Code (IEBC) in my case. Yes, I will be running my plan by the home inspector to confirm any local requirements, but I want to show up prepared.
This is the relevant foundation profile visualized:
Take note of the lack of floor joists. This is due to the pier-and-beam construction of my home, where the next joist/beam is 4 feet away from the rim joist, which is out of the render. The thick cardeck sub-floor handles these long spans.
I have considered some commonly available products, and here are my thoughts on them so far.
Standard expansion/adhesive bolts
These are not an ideal option for me due to the rim joist placement and the 9.25" clearance. My hammer drill alone is longer than this. I would need 8.5" bolts (minimum) to clear the 7-inch concrete penetration requirement and the 1.5" sill plate.
Universal Retrofit Foundation Plate (URFP)
These plates are great for getting around the inconsistencies of many foundations, and they address plates that are greater than 1.5" away from the foundation wall. Unfortunately, they are designed for direct contact with the sill plate, and I have so far ruled out this option because I would need to remove 2" or more of concrete from half of my home's foundation.
Flat Retrofit Foundation Plate (FRFP)
These flat plates look closer to the examples in the code reference A304.3.1.
These could work with the "shimming" concept called out in the code A304.3.1(2)
a. If shim space exceeds 1-1/2 inches, alternative details will be required.
b. Where required, single piece shim shall be naturally durable wood or preservative-treated wood. If preservative-treated wood is used, it shall be isolated from the foundation system with a moisture barrier.
My concerns with this approach are the max shimming depth of 1.5" and the materials called out for use. In my case, the "shim" already exists, and it's the concrete lip. Concrete is not listed as an acceptable shim material.
Alternative Options
I have considered the possibility of installing FRFPs on the exterior of my home, but aesthetically it is a last resort for me. These would be plainly visible along two sides of my home and will interfere with my siding, and therefore the resistance of my home to the elements.
I have (not seriously) considered the option of using standard expansion/adhesive bolts by attempting to drill from the floor or plate above. I would need to plug the holes this creates, I would need a very long drill bit, and the bolts would be very close to the rim joist. But it is another last-resort option to consider.
Question Summarized
In the IBC/IEBC 2021 code iteration, what are the acceptable methods of installing seismic foundation anchors for an existing foundation profile such as mine?
