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Old 06-02-2008, 09:23 AM   #1
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Deck beam Question


One section of my deck will be supported by a 6x12, 24' in length. It will be held up by three 6x6 posts and connectors shown in the picture. I was wondering if I would lose much by using two lengths of 12' with the seam directly over the middle support. The post heights are 6' and 8' at the ends. It would be significantly easier to put up in two pieces but I'm concerned about loss of lateral stability.
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Old 06-02-2008, 09:46 AM   #2
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Deck beam Question


Don't quote me on this, but as long as the the 2 12' pieces fall on center of the 6x6, I would think you would be fine. You might have some trouble keeping both sections completely level on the same plane, but as far as stability, I wouldn't think it would be an issue. Obviously one piece would be the best, but I had a 20 ft beam and it can get heavy real quickly

You might want to consider pouring the middle footing a little larger than the rest, since the center will carry more load. If the rest are 8" diameter, pour the center at 12"

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Old 06-03-2008, 11:12 PM   #3
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Originally Posted by cibula11 View Post
You might want to consider pouring the middle footing a little larger than the rest, since the center will carry more load. If the rest are 8" diameter, pour the center at 12"
Not sure I'm following the logic of this... why would the middle footing be carrying a larger load?

Regardless, with a beam size of 4x12 and post sizes of 6x6, the footings should be a MINIMUM of 12" diameter and 3' tall, preferably with a bell shaped bottom and 4-6 sticks of 1/2" rebar.

Yes, 2 beams spliced in one of those Simpson CCQ46 column caps would be fine. Check the two beams at the yard to make sure they are both the exact same height. Easier to level the whole shebang if you're not trying to shim up one beam...

You might run (2) 5" Ledger Lock screws through the tops of the two beams at an angle to help lock the tops together just a little bit more...

Mac
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Old 06-04-2008, 08:08 AM   #4
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Deck beam Question


I don't think you'll have any problems with lateral stability if you splice the beam in the middle of the connector. I don't think you'll be able to tell a difference.

However, what you'd be doing by cutting that 24' beam in half is taking a multiple span beam and making it two simple span beams. A beam will perform better in span if it is continuous over the bearing points as opposed to cut at the bearing points.
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Old 06-04-2008, 10:35 AM   #5
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Deck beam Question


Thanks for the input. I think I'll go with two sections. The joist span in this area of the deck isn't long, just wanted to keep the deck beam size consistent. Lumberyards have to special order a 24' long 6x12, but just lifting the smaller stuff I'm estimating it would take three extra guys to get it up there. I will definitely check the height dimensions on each beam to avoid having to shim discrepancies.
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Old 06-04-2008, 10:42 AM   #6
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Out of curiosity, why are you using a solid member for this beam, instead of building it out of three 2x members bolted together? You're not gaining any strength, and you're probably paying a lot more for it. Additionally, if this beam is in any way exposed to the elements it needs to be treated...And treated material in that dimension is going to be special-order in most cases.
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Old 06-04-2008, 11:58 AM   #7
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Out of curiosity, why are you using a solid member for this beam, instead of building it out of three 2x members bolted together? You're not gaining any strength, and you're probably paying a lot more for it. Additionally, if this beam is in any way exposed to the elements it needs to be treated...And treated material in that dimension is going to be special-order in most cases.

I figured the solid beam would be cleaner, minimizing gaps, crevases and connectors where rot can take hold. It is my own home and I will be staying here for the long term and willing to spend the extra dough. In removing the 20 year old balcony in the same location, I could not put pressure on the lag bolts fastening the balusters when trying to back them out with my drill. If I did they would just spin in the wood. There was water damage in other places as well so it is a prominent issue in my mind as I put up the new deck.
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Old 06-05-2008, 08:54 AM   #8
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Originally Posted by thekctermite View Post
...Additionally, if this beam is in any way exposed to the elements it needs to be treated...And treated material in that dimension is going to be special-order in most cases.
I could see that in Kansas, not sure if that would also be the case in the Bay area - up here, we've got lots of 4x pt on the ground in the lumberyards.


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I figured the solid beam would be cleaner, minimizing gaps, crevases and connectors where rot can take hold. ... There was water damage in other places as well so it is a prominent issue in my mind as I put up the new deck.

An additional protection you can take, whether you build up your beam from 2x material or just use a 4x, buy painted L-flashing in a 2x3 profile. Install flashing on beam overlapping 3" legs on top and hanging 2" legs over each side. Seal them together on top w/ flashing tape.
Install your joists using hurricane straps (Simpson H1s) and you have no nail/screw penetrations in the flashing/top of the beam. It will help your beam remain stronger longer.
Be sure the flashing is painted as bare or galvanized aluminum will rot quickly when placed next to pressure treated wood.

Mac

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