Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Lag bolt removal and reinstallation

[Subject Prev][Subject Next][Thread Prev][Thread Next]

The removal & re-installation of  these lags, if done with care, should pose no problem with their capacity.....

however it depends on the original installation as well as the current R&R procedure.

Often times in the field lags are installed in the most brutish pilot holes, wrong sized pilot holes, electric or air impact wrench.

I would suggest that you have the currently  installed lags checked for torque capacity as a QC check on their existing condition...maybe they were installed poorly & are currently stripped out?

In the lab we often R&R'd lags on test samples.....either the SImpson "self-drilling' or convention lags but we were very careful to pilot drill correctly AND not over drive the lag.   It's pretty easy to strip them out it the pilot it too large, the wood too soft or the driver too powerful.

Power driving them until the last 1/2" or so is fine...then an experienced hand on a socket or a wrench can tell whether the installation is sound.

The problem that exists is that you have a steel / wood interface and with too much torque the steel lag can easily power through those wood "threads".

The key is to never over stress that wood / steel interface.........but if you do there are techniques & materials that will allow you to recover.  :)


On 6/19/07, Theodore Smith <smith(--nospam--at)> wrote:
I'm involved with a project where the length of some lag bolts is in
question.  They are intended to be 5/8x5".  In a couple places it has
been determined that 4" bolts were used, to avoid interference with
other hardware.  The contractor wants to remove some at other locations,
measure them and reinstall them to show that 5" bolts were typically
used.  A question has arisen about whether the reinstalled bolts are
good and whether they have their full strength.  These particular bolts
are loaded in shear.  Seems to me that with careful reinstallation, the
bolts would just run back into the original threads and work just fine,
although there might be some minor wood fiber disruption at the threads,
depending on the roughness of the bolt threads.  But I don't know of any
literature addressing the issue.  I've sent an inquiry to AFPA a few
days ago, but so far the only responses have had to do with pulse echo,
xray and such nonremoval methods, and how they may not work well with
threaded, pointed lag bolts.  Do any of you have any experience with this?

Theodore E. Smith
Smith & Huston, Inc.
8618 Roosevelt Way NE
Seattle, WA  98115
206.448.8448 Phone
206.728.2872 Fax

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at:
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*   Questions to seaint-ad(--nospam--at) . Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at:
******* ****** ****** ****** ******* ****** ****** ********