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eI am installing a deck railing that will be directly above 5 1/8" x 11" glue laminated deck beam along the front of the deck. Along the sides of the deck, it will be doubled up 2x10 joists.

I can't find any documentation about if an aluminum post can mount directly into the beam. Everything I can find is for an alignment that is offset from a smaller joist and uses blocking. Can I safely install these using 8" lag screws directly into the beam?

On the 2x10s, one side of the post would align with the joists, which I would like to use lag screws on, while the other side would need blocking. Is that appropriate?

This is for a residential structure, in Utah, USA if any of that makes a difference.

Beam Diagram enter image description here

  • Good detail, but it's still a little tough to understand what you mean; would you add a diagram? – Daniel Griscom May 18 at 19:36
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    Yeah, let me work something up. – Eric G May 18 at 19:58
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    Rough diagrams added. Nothing is to any accurate scale. – Eric G May 18 at 20:16
  • The first diagram looks good. On the second diagram i would turn the blocking so it attached to the double joist with lags and not the deck boards then use lags from above. .Or possibly a steel L bracket instead of blocking. – Alaska Man May 18 at 20:19
  • I did omit all fasteners, except for the bolts to the railing post. The blocking would be anchored to adjacent joists, and a couple other blocking cross members, on all for sides with 3" screws. (Or longer i guess on the double joist side.) Basically for those two screws, I would follow the diagrams I see for posts mounted entirely to the blocking boards. – Eric G May 18 at 20:28
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I’m not an expert and likewise did not find any direct documentation on the issue of attaching surface mount posts to a laminated beam but I did find the following information that might help you make a knowledgeable decision.

The following Fine Homebuilding video references surface mounted guard posts. The main issue appears to be that the post as desired will not have any blocking perpendicular to the Rim joist. It would also be difficult to mount a reinforcing plate underneath. https://youtu.be/lTRquLcL6Jo?t=540

About the beam itself – is it balanced or unbalanced and is the axis orientation vertical or horizontal? How the beam is constructed will impact how it reacts to shear forces. I found the following guide useful: https://law.resource.org/pub/us/code/bsc.ca.gov/sibr/org.apawood.X440.pdf

Also, how wide is the post mounting plate? You will need to make sure that the screws are a minimum distance away from the edges of the board. I found the following document helpful in looking at the calculations needed. https://www.engineeringexpress.com/wiki/lag-bolts-in-wood/

Finally, this document mentions the issues with drilling holes vertically through laminated beams and it's corresponding impact on the ability of the beam to carry a load. It may be something to review. https://www.anthonyforest.com/assets/pdf/apa/glulam/Tech_Note_Field_Notching.pdf

I have a feeling that it will all come down to whether not not the code inspector believes that the guard rail post will handle the required 200 pound static load without an issue. Without any direct documentation, I'd suggest that you verify this yourself using a test version before construction being sure to test all 4 conditions: Mid-span of the laminated beam, mid-span of the 2-bys and testing the corner connections in both directions.

Good luck and let us know how it goes.

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