Existing 2x Sill Plate 7

[alexlu168]

According to California Building Code 2001, the shear load exceeding 350 plf (600 plf if anchor bolts are half stressed), the sill plate must be 3x.

What if the existing part of building only has 2x sill plate, and the building and safety does not accept stacking an extra 2x plate/block on top of existing 2x sill plate at every bay between studs as a solution. How would you resolve this issue without tearing down or cut the existing studs?

Thanks,
Alex

 

[damstructural]

If the shear is less than 350 plf you may want to add retrofit anchor bolts to meet the 1/2 stress criteria. If not, I would work with the building official to find a way to block each bay as you describe. With proper nailing and clips, this approach is consistent with the intent of the code and it will produce the cleanest result.

If you have to upgrade the sill plate, you'll have to shore up the wall, cut the studs and move them out of the way to change plates. Then you'll have to toenail the studs, which reduces the shear transfer. Also, it will be hard to get a clean cut on those studs. You will probably end up with gaps between some studs and the sill plate.

I recommend working with the building official more closely.

 

[damstructural]

Oops, I meant if the shear is between 350-600 plf, you might add retrofit bolts.

The very best solution would be to reframe the wall, but that may also be the least practical.

I'd try the block idea again and throw in an A35 at each stud if you have to. They should buy that.

 

[alexlu168]

damstructural

Thanks for the reply. But I happened to run into a building official that doesn't buy the blocking idea. I guess there's just no way around this besides cutting the studs.

Thanks,
Alex Lu, M.S., P.E.

http://www.geocities.com/alexlu713/

 

[damstructural]

Sorry about that. Some officials just can't get past the letter of the code. The main intent of the 3x member requirement (studs too) is to avoid splitting a 2x from closely-spaced edge nailing. I've been able to get approval for stitch-nailed 2x members every time in lieu of using 3x's. I don't push it too far, but I think any reasonable engineer should be satisfied with it for most applications. Sometimes it ends up being a superior solution, like you case seems to be. Good luck.

 

[alexlu168]

I totally agree.

Thanks,
Alex Lu, M.S., P.E.

http://www.geocities.com/alexlu713/

 

[RockEngineer]

This may not totally be the answer to this question but APA published a report of tests using double 2x instead of single 3x lumber for these high shear load wall diaphragms. It is TT-076 Shear Wall Lumber
Framing at

http://www.apawood.org/level_c.cfm?content=pub_tch_libmain

APA recommends getting rid of the requirement for single 3x lumber and allowing double 2x.

 

[alexlu168]

Thanks RockEngineer

This is very helpfull.

Thanks,
Alex Lu, M.S., P.E.

http://www.geocities.com/alexlu713/

 

[boo1]

Nice link Rock, you got my vote.

Ever wish these charts were based on real life construction practice????

 

[boo1]

The FEMA 450 Commentary (2003 NEHRP Commentary), Section 12.2.3.11 and 12.2.3.12 on page 237 discusses that there was splitting in the sill plate in testing and observed in earthquakes that the larger plate washers intended to mitigate.

 

[CTruax]

Alex;
I suggest requesting a meeting with
-Disagreeable plan/code checker
-Their supervisor (which can even be an elected official)
-The building owner
-And yourself
To discuss the validity of your engineering approach and the section of the building code which gives the building official the authority with which to accept alternate analysis.
The purpose of the code is to protect public safety, not cause undue hardship or expense to building owners.

State the above, in a letter, along with your calculations and references, and they will probably accept it and never having to have the meeting. Sometimes the building official just needs to be shown how to accept good engineering.

 

[CSEllc]

It has been my experience that you don't want to "show-up" the builing officials. Especially if you plan to work in the area again. You don't want to "bruise" his ego.

If I am not mistaken, the code allow for alternate review. It does nbot say the building officials must accept it.

 

[mkberry]

I sit on a board in my little town called the "Building Code Board of Appeals" with several other engineers, architects and builders to specifically address issues like these. You would make your case to our board and we would then recomend the building official accept or deny the request. Check the municipality to see if they have a similar process. Even if it's too late for this project, it's good to know this option is available.

By the way, I have used double plates nailed together without a problem on 2x6 walls. You just have to make sure the framer doesn't just nail into one plate.

 

[pmkPE]

In addition to this forum I also "watch" the seaint:digest threads. They are also very informative. Many of their questions and topics involve wood framed structures for the California vicinity. They had a recent post which cross referenced Mr. Bill Allen's web site where he offered the following link regarding this specific subject:

http://www.allendesigns.com/SWPanelJoint.htm

You may want to also address your question to their forum.

By the way what other forums are "out there" that are similar to the seaint and Eng-tips?