High seismic mudsills... must be 5.5" in width? 1

[ampersand]

I'm in California, and we just switched over to the IBC. One new requirement is that shearwall sill plate anchor bolts now have to have 3"x3"x0.229" plate washers. Now, suppose you have a shearwall built on a framed floor, and the floor framing bears on a mudsill, which sits on the foundation. Because the mudsill will have a 2x rim joist at the outer edger, which robs me of some room, it seems that I will always have to use a 2x6 mudsill in this situation. Or 3x6, depending on shear loads.
This is not a big deal for new construction, but now, every time I build a new shearwall over an existing foundation, I'll likely be working with a 2x4 mudsill, which is not big enough, so they will have to remove the floor framing, replace the mudsill, replace the floor framing, etc. A lot of extra work for a small project.
Does anyone have any thoughts on this?

 

[msquared48]

I don't understand where the problem is here. If you have a 6" concrete stem wall with a 2X6 sill plate, th floor joists sit on the top of the sill plate, 1.5" in from the edge and the rim joist on the outside. The exterior extends below the level of the floor sheathing to the bottom of the treated 2X6 sill plate. The same construction applies with an 8" stemwall.

Mike McCann
MMC Engineering

 

[ampersand]

Hi Mike,
What I am dealing with is an existing foundation with an existing 2x4 mudsill. I am adding a second story to the building, but would like to keep the existing foundation and lower floor framing. The size of the foundation is OK for two stories, but I have this problematic existing 2x4 mudsill, with a 2x rim joist- giving me 3.5"-1.5"=2" of available mudsill width to install new anchor bolts with plate washers. But IBC requires 3" square plate washers, so it looks like I have to remove the floor framing and mudsill and install a new 2x6 mudsill.
Would you use 2" square plate washers, and call it OK, because the washer does cover the entire available width of the existing mudsill?...

 

[msquared48]

ampersand:

Look to solving this another way with another shear connector. Simpson makes several retrofit connectors - look at the UFP and FAP connectors, both installed to the concrete with Titen Hex-head screws, and nailed to the sill plate. They mount to the sidewall of the concrete stem wall. Hence there is no problem with any anchor bolt washer dimensions as no additional anchor bolts are needed.

Personally, I would install enough of these new anchors to take the total shear regardless of the presence of any existing anchor bolts. If you have existing anchor bolts, just leave them in place for additional resistance capacity, up and above the new Simpson anchors.

Hope this helps.

Mike McCann
MMC Engineering

 

[skier1578]

fully agree with Mike