Lag Screw into End Grain of a 2x8???

[smitty9898]

I’m looking into possibly requiring the installation of a ½” diameter lag screw into the end grain of a 2x8.

Obviously I have several concerns regarding this:

1. Constructability: I’m concerned that when the lead holes for the lag screws are drilled, the contractor will damage the 2x8. Would requiring an epoxy screw help to mitigate any damage?

2. Has anybody had experience with this type of connection?

 

[woodengineer]

Smitty9898,

How is the lag being loaded? Attaching into end grain should be avoided. For either shear or withdrawl the NDS provides a cooresponding C(eg) factor (end grain factor)

Jordan

 

[smitty9898]

The lag screw is being used to attach a 2x12 ledger flush against the ends of 2x8's.

The withdraw load on the anchor is approximately 80 pounds, the shear load is approximately 100 pounds. I'm also installing masonry epoxy bolts for the ledger, which will take some of the shear load.

 

[woodengineer]

The NDS code does address combination shear and withdrawl loading Z for lags into endgrain.

Jordan

 

[smitty9898]

Woodengineer,

Thanks for the response! Do you know what section (or page#), addresses the combination shear/withdrawl into endgrain?

Any experience with epoxy bolts into wood? Do you think it would be a more durable connection, as compared to a lag screw?

 

[woodengineer]

For the NDS 2001 it is found in Appendix J (NON-MANDATORY) solution of Hankinson Formula, Page 161.

Ceg = 0.67 into end grain. For a lag bolt in end grain Fem=Fe(perp)

I have no experience with epoxy bolts into wood. Check with the manufacturer rather than creating a solution.

Good luck!

Jordan

 

[Ingy]

I may not be picturing the connection correctly, but how about blocking between the 2x8s and attaching the 2x12 ledger to the blocking? Better connections. I'd avoid end-grain lagging if at all possible.

 

[rday]

How about inverted joist hangers for the the 2x12 ledger connection to the 2x8 ends?

I also would recommend, avoid lagging to the end grain if possible.

 

[Slowzuki]

The inverted joist hangers is better than my idea but

http://www.socketsystems.com

sell pre-drilled purlin clips that are a 1/8th or so thick steel angle with predrilled holes.

I'm using them to attach a fascia to cantalevered 2x6's so it can be installed from the roof (difficult to get to the face of the overhang, 26 ft above ground on a hill).

 

[ornerynorsk]

Past experience, try to avoid fastening into end grain. Not a good idea.