How to construct deck beam?


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Old 02-19-09, 08:52 AM
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How to construct deck beam?

I could use some advise on how to a construct a double 2 x 10 deck beam. There are 3 6x6 posts spaced 12 feet apart.
The drawings call for 2x10s 0n each side of beam with ledger notch of 3/4 inch into each side of post and fastened with 2-1/2 " carriage bolts. The problem is I can't get 24 foot 2x10s, so both boards would have to join on center post. Seems like it would hard to drill 4 holes that close thru a 6x6. Help...
 
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Old 02-19-09, 02:05 PM
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I do not know where you are and where you got the plans but around here (Southeast PA) we would need more posts. A span of almost 12 feet is too far for 2 x 10's. You can drill four holes and break the beams over the center post with no problem. If you wind up using more posts I would break one 2 x 10 on one post and the other 2 x 10 on a different one.
 
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Old 02-19-09, 03:36 PM
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Hi klally and welcome to the board. In some areas decks fall under the permitting process and require an inspection. Where this is outside and will be obvious, you should check to see if a permit is needed and ask what they require for structure. Bill is correct that the span is a bit long for 2x10ís and as you mention, they donít make them 24í long. I could suggest some options, but they may be mute as the town may have their own ideas. Thatís where to start.

Bud
 
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Old 02-19-09, 04:30 PM
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klally,

Indeed, welcome to the forums.

First off, where are you at? Having to build a beam out of dbl 2X's is a right coast thing. They can't grow trees there large enough to get a 4X (other than a 4X4) out of. On the left coast, it's different!

You'r not going to span 24' with a dbl 2X10 beam. You're going to have posts in between to support that beam, so that's where your beam breaks -- on top of the posts. Depending on the species of wood that you are using, you posts are going to be about 8' to 10' apart.

There is no need to build up the beam. Simpson (and US Steel) make post-to-beam brackets for attaching a dbl 2X beam to a 4X post with no filler in the beam.

What I would do with a beam like that is break the 2X closest to the house on the even numbered posts and the 2X farthest from the house on the odd numbered posts (or vica versa). It's not going to get any stronger than that!

And why 6X6 posts?? 4X4 posts under a dbl 2X beam are all that's needed. If you were putting in a TRIPLE 2X beam, then a 6X6 post would be called for.
 
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Old 02-19-09, 05:26 PM
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I should clarify a few things first. I have plans from an architect and the plans have been approved and have received a permit.This is a two story front porch.The porch is approximately 25 ft. wide. There are 3 24 inch concrete piers that come up grade. The centers of the piers are 10 ft 1 3/4 inch apart. The beam needs to about 24 ft long with beam extending past end posts.The posts will be 6x6 12 ft lg.
There will be two beams actually, one under first and second level joists. The way it is drawn it has 2x10s on each side of the 6x6 posts thru bolted. I thought it might be hard to drill 4 holes on the center post so close to ends of 2x10s. Drilling all the way thru one 2x10 then 6x6 then thru other 2x10 and coming out in right spot.
 
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Old 02-19-09, 05:30 PM
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I also forgot to add that we're using 6x6s because posts will boxed into finished columns.
 
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Old 02-19-09, 05:59 PM
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klally,

Post HEIGHT was my other question, and now you've answered that. Yes, you need the 6X6 posts due to their height.

You aren't going to find 24' long 2X's for the beam. so you will have a splice in the beam at the center post. Given your 6X6 posts, you'll need a TRIPLE 2x beam -- that's the only way the BC's are made. A Simpson BCS2-3/6. What I would do is to use a 2X10 closest to the house that spans from the center post to the outside edges, same for the 2X10 farthest from the house, and the center 2X10 would break on the 2 outside posts -- or vica versa. Either way, it doesn't matter -- one is as strong as the other. Run it by your architect.
 
 

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