What is the technique/design procedure for nail laminating wood beams

[Devin2]

I am designing a monoslope roof for an ag facility. Due to the large span, I am going to have to nail laminate two 2x10 beams together to beef up the section modulus of the rafters. What is the technique/design procedure for nail laminating two wood beams together?

 

[PSlem]

I assume they share the load so they do not need structural fastening, just something to keep them together for handling. I do nails at 16" centers near top and bottom since that's the length of my hammer so measuring is easy.

 

[msquared48]

If these are continuous 2X rafters with no splices, then just use a good construction adhesive and (2) 10d nails at 12" on center staggered throughout the length.

If you have splices to increase the length of the rafters, that's a different animal.

Mike McCann
MMC Engineering

 

[Devin2]

No splices. The intent of nail laminating them is for load sharing as well as beefing up the section modulus. As such, so it is critical they act as a composite structure under loading. I wasn't sure if there was a prescribed method as noted in NDS regarding built-up columns. Thanks for the input!

 

[msquared48]

Except if the plywood panel joints are continuous along the entire length of the rafter, which is not a good thing to do, I would not really worry about this. Technically, 50% of the pl;ywood lanels should be continuous across the rafters for a 24" rafter spacing, imparting load to both sistered members. No worries.

Mike McCann
MMC Engineering

 

[Devin2]

Okay, I see what you are saying. Thanks for clarifying the load path/transfer!