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markumz
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# Posted: 27 Mar 2020 13:31
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I currently have (12) 6x6’s in the ground for my 20x24 single story. For the 24’ length, I have 4 posts in a row. In other words, I have a total of 3 rows that are 24’ long; with 4 posts in each row. I plan to make my (3) beams 24’ long using (3) 2x12’s and setting them on top of the 4 posts. Beam design & construction info has been pretty consistent across the web; you must stagger (overlap) the (3) 2x12’s as you sandwich them together. What has not been consistent is info on whether or not the staggered sections should or must have a post directly under it. So here are 2 questions: Should I just make the beam 24’ long in one single piece and set it on top of the 4 posts and not worry about where the staggered sections fall, even if it’s between the posts? Or, should I assemble the beam directly on top of the posts, constructing it as I go along from post to post, thus insuring that all staggered joints have a post underneath? The 4 posts are not spaced exactly 8 ft apart and vary maybe 4-5’ in either direction due to the many huge rocks (boulders) that I encountered while digging the holes here in SW Pa. Thank you in advance for your responses and time, this is a great site and a HUGE help to so many people.
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ICC
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# Posted: 27 Mar 2020 13:50 - Edited by: ICC
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The short answer is that yes, the joints or splices must be located over a post. The long answer is that joints/splices can be slightly off the post, positioned at the inflection point. To be dead on, that requires an engineer under the building codes used in the USA. Canadian codes have some prescribed methods that they accept, but those will not pass a code inspection in the US. It's up to you if you are trying to fly under the radar.
To the question as to whether or not to build the beam on the ground and then lift it into place, or to build in on the posts, I have to ask, "do you really want to lift a 24 foot long triple 2x12 beam?" It is much easier, more practical IMO, to build the beam in place and place the splices, staggered, over a post.
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markumz
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# Posted: 27 Mar 2020 15:00
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Thanks ICC. Yes I have thought about the weight of a 24' beam. I read on some construction site that said always construct the beam on a flat surface, never construct it on the posts. I can't recall exactly why but assume to make sure it's flat & even, which kinda makes sense. I'm getting the wood tomorrow & will start going from post to post. Thank you very much for your input ICC.
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ICC
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# Posted: 27 Mar 2020 15:17
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Use something like a good water level to get the post tops to the same height. If the tube connecting the ends is large enough they are very quick and very accurate. And unless the flat and level worksurface is very good concrete who is to say it is planar; that is has no dips or rises? Most work sites I have been on are bare, maybe graded, earth. The concrete may come after the project is done.
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Brettny
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# Posted: 27 Mar 2020 16:20
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I would build it on top of the notched posts. With a 24ft girter I would use two 12ft boards and 8ft in the middle. Post on each end of the 24ft span, one in the center then one at 1/4 and 3/4 span. You would be pretty darn close to having a post under each splice.
What's your post spacing now? This really depends on what length wood you should use.
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markumz
Member
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# Posted: 27 Mar 2020 19:22
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On center, the spacing is approx 8’3â€, 7’8†and 7’8â€.
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toyota_mdt_tech
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# Posted: 27 Mar 2020 21:14
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Quoting: ICC Use something like a good water level to get the post tops to the same height. If the tube connecting the ends is large enough they are very quick and very accurate.
Add food coloring to make the water super easy to see also.
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markumz
Member
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# Posted: 28 Mar 2020 09:21
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10-4. Bought some clear tubing last night!
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Brettny
Member
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# Posted: 28 Mar 2020 18:26
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With your spacing of you want a splice over a post your going to have waste. You will need a 10ft then two 8ft. I would still use a 12, 14 or possibly even a 16' in there.
Just out of curiosity you should check the price on 24' 2x12. They do make them and most NON box store lumber yards would have it or can get it.
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markumz
Member
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# Posted: 30 Mar 2020 17:04
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Thanks Brettny. I got (6) 8's & (3) 10's for my first of 3 beams and put the beam up on Saturday. Transporting anything longer (even 12') is tough with a small pickup though. BTW, I did have my 6x6 posts custom treated to ACC & CCA specs by a local lumber yard that specializes in treated wood; .51~.55 retention factor they said..can't recall what the box stores are treated to, .31 I think. They guy that ran the pressure tank asked me if i was planning to use them in an Louisianna swamp, so I guess they're good for pretty severe applications, even though I'm only in SW Pa. They were only about $10 bucks more each than a standard PT 6x6x8 at Home Depot. I'm doin' this project on the cheap like everyone else but I think it was worth the extra $120 bucks.Thanks once again to all of you for your quick responses. This is a fabulous site...
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