Wood Shear Wall Stud Straps

[Engrman]

It has been my practice that when detailing a wood shear wall to specify simpson straps tieing upper studs to lower studs at 4'-0" o.c. in addition to the holddowns at each end. It just seems to me that the wall should behave better if this is done. A contractor on one of my projects is screaming bloody murder about it. Does anybody else do this? Am I just being too conservative?

 

[boo1]

I assume this is a framing connection for uplift wind loading in a two story house and hold downs for shear wall segments. These requirements are standard pracice in high wind load areas. Current high wind load codes like SSTD 10-99 and 2001 Florida Building Code building methods requiements are even tighter with anchors at each stud, HDA hold down required on each side of each opening and floor to floor straps 16"O.C.

If the load analysis indicates some holddowns may be omitted but, this may cause confusion for framing contractors, the builder and inspectors.

Cheers

 

[DaveAtkins]

I would typically nail the bottom plate of the upper wall to the rim board, and toenail the rim board to the top plate of the lower wall. Of course, you have to justify the nails and toenails in withdrawal (I am in Wisconsin, where wind loads aren't terribly high).

 

[JAE]

I would first check to see if you indeed have a net uplift on the particular wall you are designing. If not, then the straps would not be required technically...although they would certainly help in a hurricane region.

Most codes do not require this unless there is an actual force that you are required to holddown. Now boo1 is probably right that in Florida and other hurricane zones, the codes may actually dictate that you use a certain capacity strap at a certain spacing...but most other areas of the country do not require it.

Where, roughly, is your project?

 

[Engrman]

Maybe I should clarify myself here. If there is uplift on the wall I design the straps to handle it. But just for peace of mind I put in straps even if there is no calculated uplift. I'm a belt AND suspenders kind of guy (I don't actually WEAR both belts and suspenders but you get the idea). I am in Colorado, near the front range where the massive fire is now burning. Design wind speed here is 85mph, Exp. C.

 

[JAE]

Well, then your question about "am I being too conservative" is answered in the affirmative. But you might want to consider discussing with your client that they are paying for your suspenders. They may or may not agree with you that THEIR money is worth the extra cost when it is not required by calculations.

I understand that the codes are a minimum, and engineers do and should consider cases where they would like to add some safety factors due to limited knowledge of conditions or loads. But there is a point when you go way beyond the code and cost the owner money (thus the screaming from your contractor.

It's a very subjective decision and all I'm suggesting is that beyond a certain point, it seems ethical to include the owner in the choosing of the final level of safety.

 

[boo1]

In the lower wind loading areas as your, the strapping is not the norm, so since your calcs do not require them I would omit them. With the legal liabilty issues and the industry leaning toword CYA no one can fault you design. I have found nail spacing (roof decking and wall) and some times shear segment hold down of more value than stud straps.

Are there sesmic loadings?