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beam spans for different sizes?



i have nine 6x6 posts in the ground and am ready to build

the total area is 20 sq ft. (outside corners of posts)

the height is 2 feet above ground.


from the outside of the outer post to the middle of the inner posts is equal to 10'


img for ref


I was wondering if i could use 3 double 2x6 as support beams, or if that would not be enough.


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Posted 2012-08-21T14:55:43+0000  by NerdrageIMO NerdrageIMO

sorry i thought img tags worked here

Posted 2012-08-21T15:13:05+0000  by NerdrageIMO


Hello again,


A triple 2x6 beam over a span of 10’ feet should be more than sufficient for normal deck loads.


Maximum span for a single 2x6 #2btr yellow pine is around 9' feet. So YES you should be fine with triple 2x6..


Are these beams getting spliced or you're using 20' boards? If they are getting spliced than make sure to alternate the boards for ex. (16' +4' _________+____, 4'+16'___+_________ etc.) Also bolts used need to be carriage type min. of 1/2" hot dipped galvanized, stagered every 16”-24 " inches ex.    , '  , ' ,


It would be much easier if were to get 20' lengths, are you having any overhang on the beam or they’ll be sitting flush with the posts?


Connector from post to beam should be galvanized 6x6 ZMAX type or similar code approved.

 6x6 zmax.jpg


Hope this helps,







Posted 2012-08-21T16:15:36+0000  by George_HD_CHI

thanks for the prompt reply..


i was actually asking if double 2x6 would be enough..

the beams are actually 2x6x10 becausei  would have to get 20' beams delivered.

Posted 2012-08-21T16:22:06+0000  by NerdrageIMO

Not a problem.


Sorry that was my bad. I assumed you're going with triple because it’s a 6" post.


If you're using double, than I’d go with the 2x8 boards. Technically double 2x6 would work but from my experience on anything over 8' it will bounce a bit.


My choice would be 2x8’s, you're not going to be able to sister same length boards. You need to get two different lengths in order to be able to sister them correctly, they need to overlap for a minimum of 24" inches. Would you be able to transport 12' lengths?, you could get 12’s and 8s if you don’t any overhang on the beams...

Posted 2012-08-21T16:41:02+0000  by George_HD_CHI
would three 4x8 work better than sistered 2x8?

also what do you use to attach them end to end?
i figured each beam would be comprised of a total of 4 boards...

do you have an image reference? i cant see mto get all of this together in my mind lol
Posted 2012-08-21T16:47:19+0000  by NerdrageIMO
whne you say sister the beams i have three things in mind
1) the triple 6x6 sistered connection
2) the double 2x6 sistered connection 1

3) the 2x6 sistered connection.

Posted 2012-08-21T17:53:49+0000  by NerdrageIMO

This is how your triple beam should look like.


Notice how short and long lengths are alternated and bolts staggered.Thats done so there is no butt joints right on top of the posts.3.JPG


Notice how beam sticks out past the post..that’s called beam allows you to place posts closer together reducing spam of the beam. Also it makes footing and post less visible once the framing goes in place.

Posted 2012-08-21T18:25:52+0000  by George_HD_CHI

thanks now i see. would the same apply if i were to not use overhang?

i already have the posts in the ground with concrete.


i can easily get 2x10x12s ... if it becomes too difficult im just going to have the 20s deliverd.

Posted 2012-08-21T18:30:18+0000  by NerdrageIMO

Yes, same method would apply if you were to not have an overhang.

Just so you know with the double beam on top of the 6x6 you would have to add a piece of block where beam connects to the posts so that you can make up for the difference in thickness. Double beam is going to be 3" inches thick triple beam is 4-1/2" inches ...your posts are 5-1/4" .you can bend you connectors with triple beam but with double you need to add a piece of block.


I use plywood fill ...or  whats called a flitch;









What size are your joists...? You should also consider doubling up your center joist..

Posted 2012-08-21T18:49:39+0000  by George_HD_CHI

If you ask me I would go with the 20’ boards and have them delivered… don’t forget all of the hardware you need to purchase in order to be able to sister shorter lengths …are you purchasing this from Home Depot? :smileyhappy:

Posted 2012-08-21T18:56:31+0000  by George_HD_CHI
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