Re-use of wood screw holes in tension application 2

[atrizzy]

I have a condition where a set of trellis joists is being supported from the underside of a beam via heavy duty 1/4" wood screws. Therefore, the joists are being supported exclusively by tension/withdrawal/head pull-through of the screws.

The contractor forgot to install the necessary plate washers when installing the screws, so in the current condition the system fails in bearing/head pull-through.

What is the consensus on removing the screws and re-using them after installing the necessary washers? I'm, of course, concerned that a second install won't be as robust as the 'virgin' install. Since the system works on tension capacity alone, I don't want to compromise this load path at all.

I'm considering having them increase the screw size.

What does the group think about this?

Thanks in advance!

 

[driftLimiter]

I agree that you can't compromise on this. I would check with the manufacturer of the screws about using them again in the same hole. There are some wood epoxy products that might also help you get a reliable installation in this condition.

Some ideas other than that you could consider longer screws, bigger diameter, some side plates with fasteners in shear, steel framing clips.

 

[skeletron]

If it was me in a DIY situation: substitute with longer 5/16" screws and use some sort of adhesive in the previous holes before re-screwing. Not sure how I would pencil this out in a structural application but it could work.

Can you move the screw locations back/forth by ~1.5"?
Can you use a thru-bolt with countersunk nut and washer at the top of the beam, instead?

 

[Deker]

Could you back the screws out slightly and install something like this?

https://www.mcmaster.com/slotted-washers/easy-install-slotted-washers/

 

[dhengr]

Atrizzy:
Of course, the biggest concern is that on the second application, you cross-thread the screw in the holding piece, and significantly diminish its holding power. There is just no way to rate the screws for that arbitrary condition. You might argue that one or two joists on a garden trellis coming loose is probably not a life-n-death situation. You’ll see them loose or leaning before they really disengage and fall down With the contractor working slowly and deliberately you/he can often feel the screw drop into the old threads, and then the first few turns take very little effort. Of course, he has to do this by hand, not with an impact driver. Once he’s got them started properly, he should be able to drive them home with a plane screw driver motor. I’ve had good luck with epoxy into the holding hole, and some on the end of the screw too. My thinking is that this certainly hardens up all the wood fibers around the screw to a condition which is probably better than the raw wood. Still try not to cross thread the screw. A 5/16" screw, same length, would seem to be o.k., and you only have to re-drill the hole in the beam for clearance.
I’ve never ‘penciled this out’ either, nor have I run any pull tests on raw wood vs. epoxy in a possibly cross threaded hole.