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I’m in the process of building a deck in Ontario, Canada, and I’ve followed a design from Home Depot. However, I’m having concerns about the connection between the post and beam or rim joist as depicted in the first picture (please refer to attached/link).

After some reading through various instructions, I’ve come across information suggesting that the through bolt connection might not be the ideal choice due to the potential for shearing failures. These instructions indicate that such a connection isn’t meant to support the deck.

If this is the case, how might I go about fixing the issue? I’ve noticed that they might have notched the 4x4 post and positioned the joist from the inside to ensure a more secure connection. Can anyone confirm if my understanding is correct?

For context:

• I’m using a 2x12 for the beam • 2x6 for the joist • 4x4 for the posts • The total deck height is set at 21 inches.

I've come up with a potential solution to the problem. I've attached my design for your review. Do you think it's feasible, or does it not fully address the issue?

Any insights or suggestions would be greatly appreciated! Thanks in advance.

current connection enter image description here potential solution

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  • Is there any reason not to put the beam on top of the post for the greatest weight holding?
    – crip659
    Sep 7, 2023 at 17:43
  • Initially, I followed the instructions provided by the Home Depot software, which indicated using a through-bolt and two sizes of lumber for the connection. But, after building it up, I did further research and realized such connections might pose potential risks. I'm uncertain if it's still okay to use or if I need to rebuild it. If the latter is the case, I'd have to purchase two new 2x12x12 lumbers and reconnect everything
    – agnes777
    Sep 7, 2023 at 18:27
  • Might depend on the grade and size of bolts used. Grade 2 is weak, grade 8 should be strong enough. Stronger than the wood.
    – crip659
    Sep 7, 2023 at 18:52
  • I used FastenMaster Thrulok 8 Inch - Model # 215-237. Do you think it is strong enough? Thank you
    – agnes777
    Sep 7, 2023 at 19:09
  • Just checked, it might be the weak Grade 2. How about the solution I posted in the last figure?
    – agnes777
    Sep 7, 2023 at 19:15

1 Answer 1

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My intuition is that your connection strengths are adequate, especially if the connection details were actually provided by Home Depot. Hopefully I can talk you down off the ledge before you waste a bunch of resources fixing a non-problem. If there is a problem, then a solution from additional fasteners is cheaper, easier, and perfectly sufficient.

Notching the posts is nice because it transfers the loads through a large area of wood bearing on another large area of wood. If you think about a bolt's load transferring mechanics, the beam's weight is sitting on top of a relatively small area of bolt. Crushing of this wood around the bolt always contributes to the failure of these connections (ideally this failure occurs after the connection has reached its design strength). The most intuitive failure mode is the single shear connection's "Mode Is" failure from

enter image description here

There are other modes where your connection would probably fail before a Mode Is failure, but looking at all of the figure's failure modes, you can see from the faint black speckling that all of these modes involve crushing of the wood. A notched post massively increases the amount of wood crushing required for failure and is therefore stronger than many bolted connection details.

Without bolt diameters and lumber specifics, I can't compute the strength of the connection shown in your first photo. Since you're in Ontario, however, there's a good chance that regionally you're stuck with SPF lumber (anything else would be stronger, I think--I hate SPF). Assuming 3/8" bolts, I get a strength per bolt of 360# (divide by 2.2 for kg). Assuming 1/2" bolts, I get a strength per bolt of 550#. So that's between 720# and 1100# of strength for your 2 bolt connections. If this were inadequate, then I would add a bunch of nails to transition it to adequate (I want to say that each 10 penny nail would add 250# of connection strength, but for peace of mind I'll say 200#--or how about 220#? I bet you like the idea of 220#). For comparison, notching an SPF post achieves a strength of 1700# on each half of the notch, where it's possible that the beam fails in bending at midspan long before the connection's load reaches that 1700#.

I would need some post layout information about your deck to find a design load for comparison to my hypothetical strength (my methods would be from US codes).

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