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Old 07-13-2011, 08:40 PM   #1
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creating a strong beam


i have a 35' span that I want to create a 2x8 beam for. I have a 24' 2x8 Doug Fir and need to join an additional 11' 2x8 Doug Fir to that to cover 35'. what type of end joint and or strapping can be used? the beam will used to hold joist hangers every 16" for an outdoor covering. beam will be bolted to 4x4 posts spaced every 10'. thanks in advance

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Old 07-13-2011, 09:01 PM   #2
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creating a strong beam


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i have a 35' span that I want to create a 2x8 beam for. I have a 24' 2x8 Doug Fir and need to join an additional 11' 2x8 Doug Fir to that to cover 35'. what type of end joint and or strapping can be used? the beam will used to hold joist hangers every 16" for an outdoor covering. beam will be bolted to 4x4 posts spaced every 10'. thanks in advance
You would need to set the 2x8's into the post or put it on the post. You can't just bolt them to the post. The 2x8's would be doubled up along the span with offsetting joints and the joints would be over a post.

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Old 07-13-2011, 09:03 PM   #3
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creating a strong beam


i would check with a engineer before doing that , it seem like alot of weight for a 2x8 , or look into using LVL
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Old 07-13-2011, 09:10 PM   #4
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creating a strong beam


This post sounds like trouble. We have no idea what load you are going to subject this beam to, we have no idea if there is potential hazard if the beam fails, and we have no idea if you have the skills to construct what would be a very long, very flexible, potentially dangerous structural element. And you are on an internet chat group to ask how to build this beam. I strongly recommend you contract with a professional structural engineer registered in your state to design the structure. This type of design is way out of normal code, and requires professional assistance.
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Old 07-13-2011, 09:42 PM   #5
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creating a strong beam


the beam will carry 16" on center 2x8s. the beam would attach to 4 4x4 pt post sunk 3' in concrete. it will serve as an outdoor patio covering with 1/2" T&G ceiling and a "lightweight" roof. the joists opposite the beam are attached to 2x10 lagged every 16" into house.

not sure what "You would need to set the 2x8's into the post or put it on the post" means tho.....

thx
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Old 07-14-2011, 01:19 AM   #6
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creating a strong beam


ptb, I had to read your question a couple of times before I got what it was you are trying to do.

And at the risk of upsetting Daniel (who makes excellent points) I think with more information, and a slight change in plans you can reach your goal.

But a single 2 x 8 in no way constitutes a beam. That's just a joist, and you shouldn't be hanging a series of 2 x 8's off it.

For what it's worth, here's what I would do. Scrap the 4 x 4 posts and go up to 6 x 6's. Build a proper beam from three layers of 2 x 8's. Sit the beam on top of the posts, and then sit your joists on top of the beam.

You don't mention what your span will be for the 2 x 8's up top, so make sure that isn't too much. Are you subject to getting any wintertime snow load where you are? And what might the slope be for that roof?
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Old 07-14-2011, 02:30 AM   #7
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creating a strong beam


thanks for the reply. too late to change the 4x4 to 6x6s due the fct that they are already in concrete 3 ' deep and now surrounded by 2'x2' block columns. your point is well taken regarding the (1) 2x8 and i looked at some Simpson post caps that would accept 2 2x8s. I am also having a 2x12 facia board that will attach to the back of the "beam". No snow where I live and a 1/4" per foot drop for roof pitch. the joists from house to beam will span 13'... thoughts..
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Old 07-14-2011, 06:41 AM   #8
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creating a strong beam


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the beam will carry 16" on center 2x8s. the beam would attach to 4 4x4 pt post sunk 3' in concrete. it will serve as an outdoor patio covering with 1/2" T&G ceiling and a "lightweight" roof. the joists opposite the beam are attached to 2x10 lagged every 16" into house.

not sure what "You would need to set the 2x8's into the post or put it on the post" means tho.....

thx
You would cut a pocket in the post for the wood to sit in. If the beam was 2, 2x8's you would need to have a 6x6 post. Or you could sit the beam on top of the post with the correct metal connectors.
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Old 07-14-2011, 08:54 AM   #9
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creating a strong beam


ptb, it looks like Ron & I are on the same page. Since your 4 x 4's are already cast in stone as it were, you will just have to work around that.

But if you have 2' x2' columns around the 4 x 4's, are the columns not structural? How about a photo or three, that will save us 1,000 words.

Does the column extend right to the top of the posts?

I was going to suggest that you could add a short piece of 2 x 4 to the back side of each of the 4 x 4's (say 2' long with a 45 cut at the bottom end) to give added support. Then you could use your triple 2 x 8 to create the proper beam.

You still might be able to use a triple beam...are the 4 x 4's actually a full 4 x 4, or even 4 1/4 by 4 1/4? Or are they dressed down to 3 1/2". P.T. posts are very often - almost always actually up this way - full size. If that's the case I would sit a triple beam right on top, and add some sort of strapping to each side as a safety measure.

Since a 2x is only 1 1/2", a triple beam is 4 1/2" wide.

Now, the 13' span should rightfully have a row of blocking right down the center of the span. You will be surprised how much that will stiffen up the roof. You will really notice that when you are nailing your roof sheathing, which incidentally, will also stiffen up that roof very noticeably.

Good luck.

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