Lag screws into top of multi-ply wood beam

[danvines]

For lag screws into the top of a multi-ply wood beam, must one account for the minimum edge distance of each ply i.e., must the lag hit near the center of an individual ply, or can they be placed 1.5D from the edge of the whole beam, even if that means they hit too close to the edge of a ply?

 

[Eng16080]

In general, I would base it on each ply not the entire beam. If you were to place a screw exactly between two plies, I think the screw would tend to pry the plies apart. I doubt you would get good thread engagement which would limit the screw capacity, and by prying the plies apart, that would weaken the beam. Based on carpenty/construction projects I've done, having set screws between plies (by accident) I've observed this.

If the beam plies were held together really well (like by through bolting plus glue) then perhaps it's not as big a deal, but I would probably still try to avoid this.

 

[XR250]

In my neck of the woods, when 4x4 knee braces are installed on decks, they run a 1/2"Ø lag up thru the middle of the plies of the 2-ply deck band
- so it must be OK