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My neighbor's elevated deck is supported by 2 6x6 posts connected by 2 2x10 boards. The posts are notched so that the 2 boards are sitting side by side in the notch and are bolted to the post (L shaped notch at the top of the post).

I had someone give me an estimate for replacing my deck and he also said that they'll notch the posts so that they weight is not carried only on the bolts.

To me that sounds wrong. Isn't that weakening the posts?

I'm thinking of building the deck myself and I was going to have the boards run on both sides of the posts, held by bolts and nuts. Maybe a metal plate of some sort to re-enforce? Something like those plate you see on steel bridges?

Any suggestions?

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    We commonly notched 3/4 to 1", as opposed to the entire thickness of the beam member. This left a good 2" of post up the center and provided plenty of bearing. – isherwood May 11 '17 at 15:52
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    I'm quite surprised that after 6 years, nobody has come by with building codes about this. I don't have a code quote either, but AIUI, through bolting the joists to the side of the posts is no longer allowed, and my local building inspector (who is rather laissez-faire) required us to change our deck design plans from bolt-through to rest-on-top when we build ours in the summer of 2018. – FreeMan Apr 15 at 11:01
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The deck builder is correct. Notching the upright provides a shelf for transferring the weight of the horizontal members onto the uprights.

I'd rather spend my time on a deck supported by thick posts instead of a certain number of galvanized carriage bolts.

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  • How about, one notch on each side versus one larger notch? Should the post be between the 2 2x10s ? – ventsyv May 20 '15 at 20:10
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    A notch on each side vs two notches together doesn't really make much difference, assuming you're using through bolts, washers, and nuts. The 'wood sandwich' is the same amount of material in both cases. – TX Turner May 20 '15 at 20:21
  • In a properly tightened bolted joint, the weight isn't supported by the bolts, they just provide the clamping force. The friction between the two pieces is what transfers the weight. Nevertheless, I agree with you, it seems that notching the post will give better, more dependable weight transfer. It will reduce the strength of the joint to forces in other directions, but those usually aren't an issue for a deck. – Joel Keene May 21 '15 at 17:57
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Notching is problematic for me...simply because it exposes untreated pt wood and collects water at the notch, promoting rot and a potential split at the notch. At the minimum, it should be painted with a copper inhibitor.

By the same token, I have some problems with perching a 10 or 12 by on the post with the connectors made for them. They don't do much to stabilize the beam laterally, leaving that to the joist attachments.

I like the post sandwiched betweeen two beams solution, even though it's frowned on, prohibited even, at least without additional hardware.

I'm going to sandwich 6x6 posts between 2 2x10' or 12' and use simpson DJT14Z brackets to give them the primary support. They're rated at about 1200 lbs each. You'll need to figure the tributory deck load at each pier but it's not too hard. I used 60 psf snow load for the calc. The additional bolts and another trick or two can boost the load. There's no pt compromise and you don't have a sandwiched beam to collect water. I wish simpson made a beefier bracket for 6x6 posts but I think all the refernces to NOT bolting to post sides and no mention of bracket solutions scares folks off, so not many folks buy those brackets.

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    Your point is reasonable, but of all the decks I've replaced over the last 30 years, I don't recall any where rot at that location was its downfall. It's almost always at or near the ground, or at a poorly-flashed wall connection, etc. – isherwood May 11 '17 at 15:51
  • 1200 lbs each - that's not enough. My code requires 8" x 4" x 1/2" Steel Angled Deck Bracket. Which you can now buy at the store; we did our deck right after those collapses in Chicago, and so we had to make them ourselves... – Mazura Mar 13 '19 at 3:36
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If I was going to notch, I would do it on once side and keep the boards together. Another way instead of notching is to use metal connectors to hold the beam on top of the post. That was suggested to me in one of my posts: Simpson Strong-Tie LCE4. Link

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  • That's what I was thinking as well, but I'm now convinced that notching in better. – ventsyv May 22 '15 at 15:21
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Notching is a waste of time not only does it expose the less treated inner part of the 6 by 6 but since it is treated the 2x10 or 2 x 12 shrinks by at least a quarter inch. Leaving carriage bolts through the slightly less treated 2 1/2" post. Which might weaken the twisting capability of the post . The shearing capabilities of a half inch Carriage bolt are astronomical. 2 mulch per post can support a lot more than any deck will need. Therefore as a professional I prefer sandwiching the post between the 2x10's and using carriage bolts ...not notching

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  • Hi and welcome. The shearing capacity of the bolts is NOT the question when considering notching. No matter how tight one makes the hole, or the nut on the bolt threads, sag will always creep in since all the weight is placed on the surface of the shaft of the bolt (and the wood in the hole will compress) rather than across the much larger surface of the notched wood. – mike65535 Mar 13 '19 at 12:32
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Using only carriage bolts seems like it’s be strong enough based on the shear strength of 1/2” bolts. This issue is that the vertical 4x4 or 6x6 is now prone to splitting under the weight of the deck. Direct bearing with a metal connector or notching is the correct way.

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