lag bolt in middle of two ply 2x4

Parksmille · Thursday at 1:42 AM

I am hanging some weight from a small beam. About 300lbs. Normally I would use a 4x4 and drive the lag in the middle of it. Has anyone found any issues of driving a 1/4" lag bolt between the plys of a 2 ply 2x4 built up member?

XR250 · Thursday at 12:33 PM

I doubt you will find anyone to be on board with this. Although, this is how 4x4 knee-brace connections to deck beams are done in my area.

Ron247 · Thursday at 4:19 PM

Not something that sounds like a great idea. If I had to do it, I would use a larger diameter fastener if possible. The 1/4" does not leave you much allowance for the 2 2x4s getting some separation or weakening for any reason.

phamENG · Thursday at 4:30 PM

Parksmille said:
Has anyone found any issues of driving a 1/4" lag bolt between the plys of a 2 ply 2x4 built up member?

Yes

RWW0002 · Thursday at 4:36 PM

With 1/4"Ø lag you might meet edge distance even in a single ply of the (2)2x. Any way you can shift the fastener over to the middle of a single ply of the (2)2x?

Parksmille · 2025-05-02T04:35:24+0100

Ron247 said:
Not something that sounds like a great idea. If I had to do it, I would use a larger diameter fastener if possible. The 1/4" does not leave you much allowance for the 2 2x4s getting some separation or weakening for any reason.

I guess I had visioned that they find two pieces that sit perfectly flush with each other. And if they are screwed together on either side of the lag location, they should not separate very easily.

Could use a bigger fastener though.

Parksmille · 2025-05-02T04:36:18+0100

RWW0002 said:
With 1/4"Ø lag you might meet edge distance even in a single ply of the (2)2x. Any way you can shift the fastener over to the middle of a single ply of the (2)2x?

yup I could move it over.

Parksmille · 2025-05-02T04:39:19+0100

phamENG said:
Yes

Can you pls elaborate why.

Parksmille · 2025-05-02T04:54:33+0100

Sorry guys. I guess I am looking for more than just "no this is bad". Has someone tested this? My wood manual does not say you should not do this.

If you see a metal joist hanger nailed into a member with a horizontal check. Do you tell the contractor to replace the receiving beam?

If a connector is screwed/nailed into a knot, do you fail the connection?

gte447f · 2025-05-02T17:51:06+0100

Probably no one here has tested this. Maybe some one somewhere has. I strongly suspect that if you did test this, you would find that the pullout capacity of the screw would be less than it would be in a solid piece, but I do not know how much less, and I also suspect that how much less could vary wildly depending on the details of the 2 plies. This is why you will get mostly answers suggesting that folks on here would rather not do this.

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lag bolt in middle of two ply 2x4

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