Connecting or splicing beams end to end

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Old 10-24-11, 03:32 PM
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Connecting or splicing beams end to end

The deck I'm building is 21' wide, and I'm using a double 2x10 PT beam sitting across four 6x6 posts spaced a little less than 7' from each other.

I originally bought four 12' 2x10's thinking that I'd just attach them end-to-end in the span between posts 2 & 3. Fortunately, I caught that mistake before cutting any lumber and now I've changed the plan so that my end-to-end joints are on top of posts 2 & 3.

I'm planning to attach the beam to the posts by notching one edge of the 6x6's and then attaching the the beam with a pair of 1/2" thru-bolts.

Here's my question..

With the 6x6's actually being 5-3/8", I will end up with 2-11/16" of each beam sitting on the post. On these posts, I'll end up with four thru-bolts, each about 1-5/16" from the end of each beam. Does this sound ok?
 
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Old 10-24-11, 03:48 PM
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nevermind.. deleted my own reply.. Original question still stands
 
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Old 10-24-11, 08:10 PM
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Not sure I'd build my deck the way you've suggested. But I tend to be conservative in everything I build, more so than most people. Should my deck be hit by the rare but possible 100-year 90 mph windstorm, or the garden tractor running at full throttle when the little woman confuses the gas and the brake, again, or whatever, I can be reasonably sure mine will sustain little if any significant damage.

But anyway, here are a few things to think about--instead of enjoying the luxury (and safety factor) of a continuous-cantilever-continuous span arrangement, your plan will be creating 3 simple spans, connected by a somewhat tenuous single bolt connection at each beam end (where there's only 7/8" of "meat" between those beam ends and the hole edges). Also, the notch you're building into the top of each support column is a stress-raiser by itself, significantly weakening an already questionable connection.

As you've probably already started cutting up your 2 x 10s, it wouldn't make sense to elaborate on the details of how I would have put things together. Or would it (if perchance you haven't started yet)?
 
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Old 10-26-11, 03:49 PM
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I haven't started cutting yet. Will probably start the posts this evening and the 2x10's tomorrow.

I'm not sure what you mean by "continuous-cantilever-continuous". But seeing as how 21' - 22' 2x10's aren't available, I see no option that doesn't include at least some end-to-end joints.

Also, from what I've read, notched posts are the preferred way to go as opposed to having the post sandwiched between the two beam members. Other than plain toe-nailing or mis-applied strong-tie connectors, I don't know of any other way to have a double 2x beam on top of a 6x6 post.

Having said all of that, after a little more research (and the acquisition of 2 more 16' 2x10's), I came up with a better idea (I think)..

Imagine posts 1 2 3 and 4, left to right..

The 'front' beam member (~13' long, cut from the new 2x10x16) will cantilever 10" outside and across post 1, continue solid across post 2, and then end at the center of post 3. An additional 8' beam will start in the middle of post 3, continue solid across post 4 and then cantilever out about 10".

The 'rear' beam member will do the reverse. The ~13' part will start 10" past post 4, go across it and post 3, and then stop in the center of post 2. Another 8' member will go from the center of post 2, across post 1, and then cantilever 10" out.

That gives me 2 'splices' instead of 4, and the 'splices' will be overlapped with solid beams. Obviously, both front & rear members will be joined with several screws & such..

Make sense?

Next question - on posts 2 & 3 I will obviously need 4 bolts because each will have an end to end splice. What about posts 1 and 4, where the front and rear beam members are solid? Two bolts, or four?

Cost isn't the reason for my question, I'm more concerned with punching extra holes in my posts & beam members.
 
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Old 10-26-11, 07:29 PM
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A "Continuous-Cantilever-Continuous" span arrangement means that there will be no beam ends at any post. Instead, both front and rear beams will be butted end-to-end in a staggered arrangement, alternating front and rear. Based on the original 12' beams you mentioned in your first post, my idea would be to run one full 12-footer starting on the left. It will be continuous over Post 1 and 2, cantilevering 5' past Post 2. Then the remainder of the front run will be a 9' beam, continuous over Posts 3 and 4, and butting up to the first 12-footer in "midair" (not over any post, but 2' to the left of Post 3). And the rear beams would be just the reverse of the front, starting with a 12-footer on the right, and ending with a 9-footer on the left. The resulting staggered splices is what I think you're proposing using 16-footers, but I don't think they are necessary.

The beauty of the foregoing method is that no beams will have any splice holes close to the ends. Rather, the splice bolts can be located virtually anywhere in the 3' of overlap between the front and rear beams (between Posts 2 and 3). Makes for a much stronger system than drilling holes too close to the ends of members, as required if beam splices are located over a post. Also, you might want to consider using a vertical 2 x 6 "helper" on each post, behind the notch. Doing so would make for a much stronger deck-to-post attachment, strengthening the posts considerably. But doing so would require longer bolts, of course. As far as number of bolts required, I think 2 total at each post would be adequate, staggered off the grain lines, and a total of 4 distributed off-grain in the 3' common splice area of the front and rear beam runs.
 
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Old 10-26-11, 10:15 PM
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That sounds like another possible solution. It's actually similar to my original assumption, but instead of having the front & rear members meeting in mid-air, it has the joints staggered. I have the materials to do it either way, so I'll check with my inspector to see what he recommends and will approve.

Next question...

I have a 4' wide brick chimney towards one end of my deck, so my ledger is actually in two pieces - one about 14', the other about 3'. I'm double-joist cantilevered around it & all that.

I started trying to set my posts this evening. I put 2 of them up, and attached strings to my ledger boards in 4 spots (3 on the 14' ledger, 1 on the 3' ledger). I put a line level on each of the 4 strings hoping to get a set of markings on the posts within a half-inch or so of each other. Well, 3 of them were pretty close, but one of the lines (middle one on the 14' ledger) was about 1.5-2 inches higher than the other. My guess is that the 14' section of ledger is crowned in the middle.

I only had about 45 minutes before I ran out of daylight today, so I was a little hurried. I will have more time tomorrow and will fully plumb & brace the posts & try again.

Here's the question though...

Assuming I'm not able to get four perfectly matched level marks on my posts, where do I set the post height at? The lowest ledger marking? The highest? Somewhere in between? Why?

If I pick a low spot on the ledger as the basis elevation for my posts then i'll end up with a deck that's slightly sloped away from the house in a couple of spots. If I use the highest spot on the ledger as the basis elevation for my posts, I'll end up with a deck that's slightly sloped towards the house in some spots. If i pick something in the middle, I'll end up with a little of both. To top it off, the boards that make up my beam are probably crowned some, and my joists probably are too.

Any good rules of thumb to use?
 
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Old 10-27-11, 01:47 AM
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Beam splices made in "mid-air", as you call it, will be considerably stronger than any splice made on top of a post, because of the multiple holes required near the ends of the simple span beams--as long as the splices are staggered, of course. Just FYI, a Doug fir (or any lumber with an allowable, repetitive member bending stress of 2050 psi) double 2 x 10 beam is able to safely resist 5116 pounds of total vertical force at the combined cantilever ends (5' from one direction, 2' from the other) without ANY connection of any kind between the two cantilevered ends. That number (more than 2.5 tons) being based on the working stress formula of F = M x c / I = M / S, where M is the total bending moment, F is the allowable lumber stress, I is the moment of inertia of the section, c is the distance from the neutral axis of the member to the extreme fiber in bending, and S is the section modulus. Adding splice bolts through both 2 x 10s in the 3' common lap area is just insurance.

I don't like decks that have "waves" in them. A ledger should not have 1-1/2" of "crown" in it. It should have been attached to the house with as little camber as possible--1/4" or less. If it's already installed and bolted tight, you will be fighting the system in trying to get a reasonably level deck. I think I'd snap a chalk line on the lumpy ledger, and make a "corrective cut" with a circular saw, blade depth set for partial depth cut. You'll have to tack a filler strip on the ledger first, with counter-bored holes to cover the bolt heads, for a smooth surface to set the saw on. And adjust the depth of cut to not quite go full-depth in the ledger--use a hammer and chisel to clear out the last sixteenth. If your 2 x 10s have excessive camber in them, clamp them in place on top of the posts whose notches you've set dead-level, before drilling any holes. Making sure to set the notch elevations with a tight chalk line. I'm assuming your posts will be set in concrete, and allowed to "run wild" (left intentionally high, to be trimmed after you've snapped notch and top elevations on them). Don't ever "pre-notch" your posts.

Living in snow country, I've always sloped the decks I built away from the house, usually at 1/8" per foot fall. I don't like melting snow to flow towards the house, since the gaps between deck planks can't be relied upon to remain open and free-flowing during multiple freeze-thaw cycles. And I've always had at least a 3" step or more from the door threshold down to the finished deck surface, again with blowing snow (and snow removal) in mind.
 
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Old 10-27-11, 09:31 AM
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Originally Posted by BridgeMan45 View Post
Beam splices made in "mid-air", as you call it, will be considerably stronger than any splice made on top of a post, because of the multiple holes required near the ends of the simple span beams--as long as the splices are staggered, of course. Just FYI, a Doug fir (or any lumber with an allowable, repetitive member bending stress of 2050 psi) double 2 x 10 beam is able to safely resist 5116 pounds of total vertical force at the combined cantilever ends (5' from one direction, 2' from the other) without ANY connection of any kind between the two cantilevered ends. That number (more than 2.5 tons) being based on the working stress formula of F = M x c / I = M / S, where M is the total bending moment, F is the allowable lumber stress, I is the moment of inertia of the section, c is the distance from the neutral axis of the member to the extreme fiber in bending, and S is the section modulus. Adding splice bolts through both 2 x 10s in the 3' common lap area is just insurance.
I'm liking the sound of that. Of course, with me being in the engineering trade, formulas are always appealing! In the end, I have to go with what the inspector will approve, but I'll run this by him for sure.

Originally Posted by BridgeMan45 View Post
I don't like decks that have "waves" in them. A ledger should not have 1-1/2" of "crown" in it. It should have been attached to the house with as little camber as possible--1/4" or less. If it's already installed and bolted tight, you will be fighting the system in trying to get a reasonably level deck. I think I'd snap a chalk line on the lumpy ledger, and make a "corrective cut" with a circular saw, blade depth set for partial depth cut. You'll have to tack a filler strip on the ledger first, with counter-bored holes to cover the bolt heads, for a smooth surface to set the saw on. And adjust the depth of cut to not quite go full-depth in the ledger--use a hammer and chisel to clear out the last sixteenth. If your 2 x 10s have excessive camber in them, clamp them in place on top of the posts whose notches you've set dead-level, before drilling any holes. Making sure to set the notch elevations with a tight chalk line.
My ledger is up and bolted, but I've only got four bolts in for now. With that said, I tacked it up with a few nails, so pulling it down to rip it might be more destructive than it's worth. Maybe not, though. I'll think about it.. If I had it to do again, I would have picked 2 shorter, straighter boards instead of going with a single long one.

But let's take a step backwards.. With four strings & a line level, am I even going about this the right way? I checked some books and online resources, and they pretty much all say "mark your posts level with the ledger, then cut them.." I figure most people pull a single line to a single post, then pop a line at that elevation across all of the posts.

Are the articles/books I've found oversimplifying this step, or am I over-complicating it?

Originally Posted by BridgeMan45 View Post
I'm assuming your posts will be set in concrete, and allowed to "run wild" (left intentionally high, to be trimmed after you've snapped notch and top elevations on them). Don't ever "pre-notch" your posts.
Yes, my posts are "wild" and I'll be marking them in the air. Cutting though... That seems difficult/dangerous to do up in the air. Thoughts?


Originally Posted by BridgeMan45 View Post
Living in snow country, I've always sloped the decks I built away from the house, usually at 1/8" per foot fall. I don't like melting snow to flow towards the house, since the gaps between deck planks can't be relied upon to remain open and free-flowing during multiple freeze-thaw cycles. And I've always had at least a 3" step or more from the door threshold down to the finished deck surface, again with blowing snow (and snow removal) in mind.
I had a hunch that a little bit of slope was a decent idea - that was actually one of the very first questions I asked in this forum. Unfortunately, my step down is less than 3" and since I'm in a townhome, my deck elevation has to match my neighbor's.
 
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Old 10-27-11, 11:38 PM
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Pardon my being blunt, but it sounds like you're worrying this project into an early grave. If you have to match the neighbor's deck elevation, just transfer that over to your adjacent outside post, and measure down. At the other end, come off your ledger board with a level line to that outside post, and measure down. Remember, you won't be measuring down the same dimension at the 2 posts, as the one on the neighbor's side also has the deck plank thickness to subtract.
Then just pull a tight string between the 2 exterior posts you've just marked, and mark both interior posts at that line. Home free.

You've never said how high in the air your deck will be, but even if it's 10' up, just get yourself a sturdy stepladder and bungy cord it to the post (to keep it where you want it). Then take your circular saw up there and make the cuts--one completely through for overall height, and one partial-depth for your notches. And it wouldn't hurt a bit to dribble some decent wood preservative on all post ends and notches that you've exposed, lest they prematurely rot out. And also, don't forget to true up your lumpy ledger board, as I described earilier.
 
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Old 10-28-11, 08:42 AM
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Originally Posted by BridgeMan45 View Post
Pardon my being blunt, but it sounds like you're worrying this project into an early grave.
No apologies necessary. I fully admit to over-thinking things sometimes, errr... most of the time.. That comes from being burned a few times from under thinking things.

Originally Posted by BridgeMan45 View Post
If you have to match the neighbor's deck elevation, just transfer that over to your adjacent outside post, and measure down. At the other end, come off your ledger board with a level line to that outside post, and measure down. Remember, you won't be measuring down the same dimension at the 2 posts, as the one on the neighbor's side also has the deck plank thickness to subtract.
Then just pull a tight string between the 2 exterior posts you've just marked, and mark both interior posts at that line. Home free.
Our elevation has to match, but their deck (and the old one I tore out) is 7' deep and my new one is 10' deep so my posts are pretty far from hers. I can still pull an elevation off of hers though.

Originally Posted by BridgeMan45 View Post
You've never said how high in the air your deck will be, but even if it's 10' up, just get yourself a sturdy stepladder and bungy cord it to the post (to keep it where you want it). Then take your circular saw up there and make the cuts--one completely through for overall height, and one partial-depth for your notches. And it wouldn't hurt a bit to dribble some decent wood preservative on all post ends and notches that you've exposed, lest they prematurely rot out. And also, don't forget to true up your lumpy ledger board, as I described earilier.
My cuts will be at about 6' off the ground or so. I think I can handle it..

I pulled off my flashing and popped a chalk line and the ledger board isn't nearly as bad as I thought. Maybe 3/8" of an inch at the most. I re-pulled the strings and my elevations were all within a half inch. So I don't know what the problem was Wednesday night. Anyway.. I think I have it under control now. Match my end post to the neighbor, get a good elevation off the ledger for the other end post, then pop a line across the middle posts.
 
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