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I have an existing utility building built with large (8x8) timbers.

There is little, or no, shear strength in the wall diaphragms and it would be very hard to shear them with conventional plywood shearing, etc., because of the timber construction.

So I was brainstorming how to install criss-crossing diagonal tie rods in an X pattern and came across this odd picture:

https://bayarearetrofit.com/wp-content/uploads/HORIZONTAL-HOLD-DOWN-TENSION-TIE.jpg

... never mind the concrete ... can I install something like this at a 45 degree angle on the face of an 8x8 (probably 12+ inch length) and install another one on the opposite end and tighten a tie-rod between the two ?

Or, more specifically, can I do that and achieve strength that would meet, or exceed, the shear resistance of a conventional plywood shearing over typical framing ?

This picture was in the context of successful installations and was NOT a "what not to do" example ... it surprised me and I wonder if it is sane.

Thanks.

user227963
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  • "Shear" \mapsto "Sheath", right? – popham Oct 23 '23 at 04:17
  • A problem with face mounting something like this is that the rods are eccentric by half your timber thickness plus an offset from the shear center. Put a bunch of tension in such rods and they generate significant twisting loads. For wood construction you would probably have to retrofit to resist that twisting somehow. Putting symmetric ties inside and out also works, but exposure to weather is likely a problem then. How about a picture or three of your structure? – popham Oct 23 '23 at 04:23
  • @popham I understand what you mean by being offset from the shear center and I agree that is not ideal. The wall in question is literally two 8x8 timber columns with an 8x8 across the top - connections are with typical Simpson column caps. My first thought was drill in a 5/8 eye-bolt in the corners and then connect with crossing rods but the 45 degree angle on an eye bolt reduces pulling strength by 50% and it is kind of the wrong tool for the job. This picture was the first retrofit hardware I have seen that lets me "stick a tie rod into a timber @ 45 degrees" ... – user227963 Oct 23 '23 at 04:48
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    With the eccentricity I would be cautious. The IRC takes care of such considerations for light frame construction. Why not drill the holes aligned with the direction of pull? Carve a perpendicular bearing surface for the eye bolt washers? I suspect that pushing a threaded rod through would be cheaper than wire rope, eye bolts, clamps, and turnbuckles, but you would probably need coupling nuts to make hardware store threaded rods long enough. Are these box shaped timbers? Or rounds? I hear "Simpson" and I think box and I'm left confused by your rejection of traditional sheathing. – popham Oct 23 '23 at 05:07
  • @popham Thanks - yes, I was thinking of drilling a diagonal hole and threading a rod through, etc. - seems like a simple solution. However, the rod comes out the back end at 45 degrees and ... I just tighten a nut over that ? The nut would be touching just a tiny bit ... I would need a wedge shaped bearing plate or a wedge shaped washer and those don't seem to exist at a full 45 degrees ... what does the tie rod end with on the back side ? – user227963 Oct 23 '23 at 05:55
  • You could saw enough of the corner off to provide a landing big enough for the nut and washer. I see a 1-1/2" Forstner bit on Amazon for 15 USD. You could use a Forstner bit to carve the landing on the outside first, then you could use the dimple from the bit's tip to layout the start of your through-hole. If you had square plate washers, which wouldn't be a bad idea, then you could saw cut saw cut for both sides of the plate washer and then chisel out between the cuts. – popham Oct 23 '23 at 06:53
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    But why aren't you using paneling if these are square cut timbers? – popham Oct 23 '23 at 06:55

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