Strap tie holdown fix

[Power Builder Engineer]

The siding is bowing because of a buckled LSTHD, the fix has been done like this: remove the sidings, pull the strap off, flatten it and nail it back.
There are 38 nails densely nailed to triple 2x6 load bearing stud that is supporting a major beam, do you think this fix could have possibly weakened the strength of the stud because of the nail holes left behind?

 

[Pmtottawa]

My opinion is as follows

1. Do not rebend the material unless it is an acceptable practise from the manufacturer. It could be that you need more capacity than is offered.
2. The nailing pattern will not weaken the stud if installed per manufacturer's recommendations and the correct number of studs provided.
3. I would use a HDU Simpson tie down in lieu of the strap as it gives better resistance.

P

 

[Power Builder Engineer]

I understand that the nail pattern is safe if it was installed correctly in the first place. If it's pulled off and re-nail back, then the nail holes would be doubled in the stud, that's my real worry.
We have notching and Boring guideline, but do you know any nailing guideline? For instance, how many nail holes would start weaken the stud or post.

 

[mark_1155]

I think it would be ok to renail it. Tell them to fill existing holes with wood filler. What's the cause? Plate shrinkage, if so, how long did it take to bow?

 

[Power Builder Engineer]

I think it's plate shrinkage, or the builder didn't flatten the strap before nailing it. The house was built 3 months ago. Now the nail holes cannot be easily filled with wood filler because the stud is behind the OSB exterior wall. Is there a code that mentions how many empty nail holes are allowed in a load bearing post/stud?
This is not my picture, but mine buckles at the red circle.

 

[mark_1155]

NDS is the standards for nailing. I'm sure it wouldn't be in compliance. Cutting out the buckle and welding back together is a fix but no framers carry welding units. How about just sending nails through the buckle and try to flatten it out?

 

[Power Builder Engineer]

Thanks Mark.
Sorry I think I didn't make it clear in the question, the builder has already applied the fix of pulling off and renail.
My client is in a dispute with the builder because the builder insists that the fix is not weakening the structure and refuse to do further fix.
I'm unable to find any renailing standard in NDS which specify the number/density of empty nail holes allowed to leave in a stud/post/column.
Although I might be able to finally find some standards to be against the builder, any further fix at this moment would be very destructive, which may include cutting the OSB open and replacing the stud.
So I'm seeking for advice here about how much problem their fix could have caused and if the stud vertical load capacity is not weakened then I would suggest my client to accept this fix and move on.

 

[Pmtottawa]

Replace nails with either sds or sdw screws

 

[Power Builder Engineer]

Sds screw is a good suggestion for holding the strap tight to the stud, but anyone knows a standard of how many empty nail holes are allowed in a stud/column?

 

[Power Builder Engineer]

Ping...

 

[KootK]

I'd be surprised if you found the silver bullet document that you seek. And, if it exists at all, the place to start is probably by asking a technical rep as Simpson or one of their competitors. Have you reached out to any of those guys yet?

My gut feel on the holes is this:

1) I'd not be too concerned about any net section, tension failure checks on the post.

3) If you could re-use the nail holes exactly, with larger diameter nails or SDS screws, I'd be pretty comfortable with that. I doubt this is the case.

4) If the straightened strap would result in spacings between new and existing holes that satisfied NDS minimum spacing requirements, I'd be pretty comfortable with that. I doubt that this is the case though.

5) If the straightened strap would result in driving in fasteners into the edges of the existing holes, then I would not be comfortable with that. Too much slop to be taken up before engaging the post in tension and unpredictable fastener behavior. This may well be the case.

6) If the straightened strap would result in fasteners with small, but non-NDS compliant fastener spacings, I'd be medium comfortable with this but, probably, not comfortable enough to sign of on it. I believe that the spacing requirements are mostly about preventing splitting perpendicular to the direction of the applied fastener shear in this application. And and empty hole doesn't induce any of these kinds of stresses.

I expect that this will come down to a judgment call on your part. If it were me, and I couldn't get something definitive from Simpson etc, I'd probably either:

1) Have the post replaced or,

2) If the strap is weldable, weld on an extension and get your grab up above the existing holes. Although this may run the risk of setting the building on fire.

If dispute = possible litigation, I'd be concerned about your ability to demonstrate no reduction in capacity here. Conversely, if I was your opposing expert witness in such a proceeding, I'd feel pretty good about my odds of being able to eviscerate you in court.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[XR250]

I doubt the stud capacity is affected. However, having the old holes near the new holes has likely reduced the capacity of the connection. Don't know how you figure that one out.
Have you calculated the demand on the strap?

 

[Celt83]

Are you sure the siding is bowing because of buckled straps, the LSTHD are nailed for pretty much their entire length so the only piece that should really deform is at the space between the foundation and the wrap over the bottom of the wall.

Had a similar condition on some jobs in the past and on one it was improper installed siding that was screwed down so no movement between the siding panels was allowed and on the other there was no joint provided in the exterior osb wall sheathing so when the wood shrunk as it reached equilibrium the osb buckled outward.




Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[Celt83]

Re-read your post and see they already peeled these off and probably hammered them flat back into place, reach out to Simpson for a verdict on the integrity of the strap.

For the Studs check them with the incising factor to get an approximation of the reduced strength, "Evaluation of a reduced section modulus model for determining effects of incising on bending strength and stiffness of structural lumber" Roland Hernandez & Jerrold E. Winandy

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[gte447f]

I am with XR250. I would not be concerned with stud capacity for either compression or tension, but I would be mindful of the hold down connection to the stud. I would bet that by removing the nails, hammering the strap flat, and then re-nailing the nails, the builder has relocated the nails a very small distance above the previous nail holes, and I would bet that this would result in slop/slip/deflection if the strap is ever subjected to a significant tension force.

 

[Power Builder Engineer]

Thank everyone for the great suggestions.
Update:
Just had a call with Simpson engineer and they confirmed that the stud load capacity would not be impacted, the only thing is that they are unsure about how much the strap would be weakened by the flattening, it allows rebend one time only.

 

[TehMightyEngineer]

One thing to consider is that at full load nailed straps will begin to deform the nail holes and try to pull the nails out diagonally anyway. The strap should fail before the nails pull out fully but the way I see it is you've effectively just already started them down the path they'll naturally go. I agree with Simpson that the real question is can those straps take being flattened, and I'd go with KootK's suggestion that you definitely can't certify it as acceptable but in the absence of a clear indication that it's not acceptable (and it likely is acceptable to be honest) you can at least recommend to the client/owner that they let this defect slide and warn the contractor that they get only one freebie and they better run repairs by you in the future.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL, CO) Structural Engineer (IL, HI)