Notch or not to Notch Column to Support Beam with Overhead Pergola?

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Old 07-01-15, 06:54 PM
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Notch or not to Notch Column to Support Beam with Overhead Pergola?

Hello,
I am having trouble finding a consistent answer to my problem while designing a low level deck that will have a pergola above.

Picture a square deck with a 6x6 column in each corner (Deck is approx 9foot square). Each column will carry the load of the deck, for the sake of argument, the beams to support the deck will be two 2x10" PT lumber. The columns that support the deck will also be the same columns for the pergola. The 6x6 column is supported by a poured concrete footing. The deck is about 2 feet off the ground, and the pergola will be about 8 feet above the ground, so the column will be about 10-11ft long.

So, how do I attach the beam to this column to support the deck, while at the same time retaining structural integrity for the pergola? Everyone, including building code is against sandwiching the beam on the column to support the deck (and i understand why). However, If i notch the column to accept the beam, I will be removing 60% of the material in the column (to accept a double 2x10"). This to me creates a major weak spot in the column to support lateral movement of the pergola.

What is the best practice here to do this? Or is standard practice to mount a pergola column between the joists and rim joist (this just seems like a weak structure to me)?

Thank you!
 
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Old 07-01-15, 07:03 PM
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Welcome to the forums! Look at page 10 here http://www.awc.org/publications/DCA/DCA6/DCA6-12.pdf to see how standard practices handle it. You can't bolt the 2x10's to the sides of the 6x6's, as they must be let in and be supported by the vertical part of the post. Hope that answered it. If not, post back. We're here.
 
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Old 07-01-15, 08:10 PM
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Thank you for the quick reply and welcome.

I have studied that document before. However it doesn't entirely answer what I should do in this particular scenario. My Column needs to continue up and above the deck. Unfortunately, none of the building codes exactly cover this situation. They all agree that notching is the preferred method of supporting the Beam on Column. But none of them continue upwards.
 
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Old 07-01-15, 08:23 PM
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I always continue upward with posts after notching for joists or beams. What would keep you from doing so? I may not understand all you are entertaining.
 
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Old 07-01-15, 08:50 PM
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You are concerned that notching the post will weaken it's ability to support lateral (sideways) loads applied to the part of the post above the notch and you're correct, it will.

I haven't seen this particular situation addressed in the guidelines. If the beams don't have to continue past the posts you could use a double joist hanger with inside flanges (the kind you fasten to the posts and then drop the beam in) but I don't know whether it would handle the load. You might have to consult an engineer...

You could also add diagonal bracing above the deck, but that would look like hell unless you could turn it into a design "feature".
 
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Old 07-01-15, 08:59 PM
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Or use 6x8 posts so even after notching you have plenty of meat. One final thought, there is only one direction the post would be weakened and that's to force applied from the notched side toward the inside...so as to open the notch up. To counteract this you could fasten a flat strap (steel) from above the notch, over the beam to below the notch. But again...wouldn't look so hot.
 
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Old 07-02-15, 04:21 AM
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If the deck is built with lateral integrity to begin with, sway is a non issue. Bolting the members together strengthen the joint, and there should be no issue with breaking the post. It's not a totem pole. You are looking at shear, not sway.
 
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Old 07-02-15, 09:28 AM
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Yes, the deck load on the posts is shear, but he's worried about the wind loads on the pergola above (which share the same posts) stressing the notched posts.
 
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Old 07-03-15, 01:34 PM
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Thanks Carbide and Chandler for your responses.

Carbide, you understand exactly what I am saying. I will most likely attach a flat strap, or bolt lumber over top of the notched area. That will all be hidden under the joists. And I will have two Joists on either side above the notch which I will reinforce as well.

The upper pergola structure will be extremely sturdy once built. So basically the whole thing would have to go, all four posts.

I am surprised there is very little in the code, guidelines or best practices on this.

I have seen many decks built that use the 6x6 support posts up for handrails, pergolas and overhangs all the time.

Thanks again, and if anyone else has any feed back please let me know!
 
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