Need help with beam/joist layout

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Old 02-25-19, 08:50 AM
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Need help with beam/joist layout

I'm designing an odd shaped deck and could use some assistance laying out the beams and joists. Below is one option, at least I think so. The only problem area is the rearmost band board wouldn't have much to attach to, and I'd need to add a post to support a single joist at the rear intersection. This needs to be freestanding. I drew the beams as dropped beams, but maybe some combination of dropped and flush would work better.

Other questions, in general, can LUS and/or HUS hangers be used to attach the end of one beam to another beam or a beam to a ledger as opposed to adding another post? And can two beams intersect at a single 6x6 post?
 
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Old 02-25-19, 10:52 AM
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Why not modify your design so that rear rim joist meets the middle beam?
 
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Old 02-25-19, 12:10 PM
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Why not modify your design so that rear rim joist meets the middle beam?
Because the deck is already smaller than I'd like and that would make it even smaller.

I came up with this alternate layout. BTW, I am able to install a ledger at the slider only because the foundation is higher in this area.

(Red beams are dropped, blue are flush)

http://www.mediafire.com/view/o94yy9...32_PM.PNG/file

Here's another, but results in three more posts:
http://www.mediafire.com/view/tazmov...37_PM.PNG/file

And another, but way too many posts:
http://www.mediafire.com/view/5hz69m...07_PM.PNG/file
 
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Old 02-25-19, 02:09 PM
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Are you doing this project yourself or hiring a contractor? Angles and "funny" construction could cause the building inspections department to require Engineering. The big gotcha I see off hand is a lack of truss hangers and bracketry available off the shelf. If you can keep things simple and with 90 degree angles at least for the structural support it might allow you do work within the codes, with standard brackets and not need Engineering.
 
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Old 02-25-19, 02:53 PM
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Keep it simple. Here is my suggestion. (Assuming your grid is 16 inches, using 8 foot joists.) I started laying out beams first. Where they are parallel to joists they can be rim joists. I show posts at perimeter. You could set them back and cantilever I suppose. Beam from corner of house to center of right side is only necessary to support perpendicular beam from slider to top. If you put a post there instead then joist only is needed from house to right side.
 
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Old 02-25-19, 03:24 PM
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It needs to be freestanding. I have an engineered floor with a non-structural rim.
 
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Old 02-25-19, 03:54 PM
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Ok, so you would need posts at appropriate locations to make it freestanding. The suggested framing scheme can still apply but your original red beam that I x'd out would be a good substitute for the "ledger" connections. Put the post at the intersection of the red and dashed beams. Run the "red x" beam low if you can so it supports the others.
 
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Old 02-25-19, 04:23 PM
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I dont see how your suggestions differ from what I'm proposing. It appears you just ran the joists the other direction and rotated the beams accordingly. A fresh drawing would help. Reminder that I can put a ledger where the slider is because that is a poured concrete wall.
 
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Old 02-25-19, 08:30 PM
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Referencing the third diagram, can the ends of the two beams next to the house and the diagonal beam intersect over a single post, such as an 8x8? If I could do that on both ends of the diagonal beam, that would omit 4 posts .
 
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Old 02-26-19, 07:58 AM
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I shifted things around and came up with what I believe are two viable options. The viability of Option 1 depends on whether I can support the middle beam to a ledger (bolted to concrete) using a hanger, such as an HUS210-2. I believe all else meets the code requirements in my area. I should point out that with Option 1 I had to spread the joist spacing of the last two joists on the rear left to 16" o.c. to meet code (to minimize the cantilever). Would this mean I wouldn't be able to install composite decking at a 45 if I chose to do so? I plan on doing PT deck boards initially, but would like the option to use composite in the future. Option 2 is looking like the better option, as I wouldn't have to worry about hanging a beam off a ledger, nor would I need to increase the joist spacing to 16" o.c. at the rear.

Option 1: https://www.mediafire.com/view/b2hka...tion1.png/file
Option 2: https://www.mediafire.com/view/bfwmh...tion2.png/file

Question about joist cantilever: I am allowed a cantilever of 1/4 of the joist span. Is the joist span the entire length of that particular joist, or is it the distance between beam support?
 

Last edited by mossman; 02-26-19 at 08:32 AM.
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Old 02-26-19, 08:33 AM
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Are you doing this project yourself or hiring a contractor? Angles and "funny" construction could cause the building inspections department to require Engineering. The big gotcha I see off hand is a lack of truss hangers and bracketry available off the shelf. If you can keep things simple and with 90 degree angles at least for the structural support it might allow you do work within the codes, with standard brackets and not need Engineering.
I may do it myself. I haven't decided yet. It depends on the estimates, which I haven't gotten back yet. I agree on keeping it simple, which my recent two options do.
 
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Old 02-26-19, 09:44 AM
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Question about joist cantilever: I am allowed a cantilever of 1/4 of the joist span. Is the joist span the entire length of that particular joist, or is it the distance between beam support?
I suppose "span" means distance from center of beam to center of beam. Otherwise it would say joist "length". I'll have to adjust accordingly.
 
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Old 02-26-19, 10:08 AM
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Guess I could just angle the beam a little and get the cantilever I want. That way I wouldn't have to reduce the size of the deck at all. If I did so, would I still be able to use Hurricane Ties? It isn't much of an angle, so I could bend them slightly if they don't have a skewable version. Worst case I could toenail.

https://www.mediafire.com/view/h5v88...ion2b.png/file
 
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Old 02-26-19, 11:07 AM
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I don't see any intervening forum posts so I assume your latest are a series of "thinking-out-loud".

"Span" is the distance from support point to support point (in your case beam-to-beam). No need to push the cantilever to the allowable limit. Why not just cantilever a foot or two for aesthetics and clearance from existing footings?

I think Option 2b is getting close. Instead of skewing the beam why not use two shorter beams parallel to the outside edge with the support point where the perimeter changes direction. I think a 4 x 6 post there can be used to support the two beam ends. (The amount of bearing surface is the issue not the supporting capacity of the post.)
 
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Old 02-26-19, 12:45 PM
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Only issue here is I'd end up with a 5 foot beam. Guess that doesn't matter. The single skewed beam would be more solid wouldn't it?

Like this?
https://www.mediafire.com/view/pj65q...n2new.png/file
OR
https://www.mediafire.com/view/xmxtx...tRevE.png/file

The reason for the cantilever is so I don't have to worry about using skewed hangers on all the joists ends, which I'd need with flush beams.

Why not just cantilever a foot or two for aesthetics and clearance from existing footings?
I'm limited to 1/4 the joist span, which I am pushing to the limit with the most current design.

I think a 4 x 6 post there can be used to support the two beam ends. (The amount of bearing surface is the issue not the supporting capacity of the post.)
All posts will be 6x6, beams (2) 2x10, and joists 2x8 at 12" o.c.
 

Last edited by mossman; 02-26-19 at 01:07 PM.
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Old 02-26-19, 01:46 PM
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Revision E is what I was suggesting. It will be just as solid as a single skewed beam because everything will be tied together.

You can run that beam low and have the joists land on top of it rather than use joist hangers. Then nail a rim joist to the ends of those joists to close it off and provide stability.

Use two 6x6 posts (or a 6x8) at the beam joint on an enlarged footer if you have to.

That upper right post may have to move to the corner.

BTW: With an 8 foot span you can cantilever 2 feet maximum, but you could cantilever less than that. So you could reduce your cantilever to one foot by increasing the span to 9 feet. (Maximum span for a 2x8 is 12 feet and you are nowhere near that in this layout.)
 

Last edited by 2john02458; 02-26-19 at 01:48 PM. Reason: Add'l info.
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Old 02-26-19, 02:23 PM
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Like this right? https://www.mediafire.com/view/yhz41...tion3.png/file

What would the advantage be to doing the two connected beams as opposed to the skewed beam? I'm not concerned with appearance on that end because it is facing the foundation of an adjacent home and no one will ever see it from that angle. If I had to choose a side to look best, it would be the right side.

Maybe I should run the joists and beams the other way? I lose a couple inches of depth on the back left though. Not the end of the world.

https://www.mediafire.com/view/w9lbf...vEalt.png/file
 

Last edited by mossman; 02-26-19 at 02:49 PM.
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Old 02-26-19, 02:55 PM
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What would the advantage be to doing the two connected beams as opposed to the skewed beam?
Just more conventional and less likely to raise questions. Less cantilevering at the "point". Since you are not using joist hangers the skew is not a connector issue.

If you go with the skew, you might want to hang a couple of joists between the beams like blocking to add stability.

Joist layout as is will be fine for appearance from the right side. Are you going to add skirt below to close off the view under?

Oops: I did not see the RevEalt until after writing above. It looks pretty good from all perspectives. The skew makes sense. The cantilever is minimized. Minimum number of posts. Good view from right side. Skootch the vertical beam as far as you can to the left and you won't lose much at all from the top left.
 
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Old 02-26-19, 03:00 PM
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Joist layout as is will be fine for appearance from the right side. Are you going to add skirt below to close off the view under?
I was more concerned with the ends of the two beams being visible from the right. If I rotated the beams 90 degrees like my last attachment, the ends would point to the rear, which no one would see.

I may add a skirt at a later date, so I could conceal the beams that way. Good point.
 
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Old 02-26-19, 10:25 PM
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Skootch the vertical beam as far as you can to the left and you won't lose much at all from the top left.
I put it as far left as I could. The limiting factor is the overhang of that last joist. It can't be more than about 1'-9".
 
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Old 02-27-19, 07:29 AM
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That last joist is not cantilevered if it is supported at the end by the angled rim joist. You could double up that angled rim joist to consider it a (flush) beam if you have to.
 
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Old 02-27-19, 07:56 AM
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That last joist is not cantilevered if it is supported at the end by the angled rim joist. You could double up that angled rim joist to consider it a (flush) beam if you have to.
Ahhh. I see what you're saying. That helps!

Although I'm not sure I like the idea of using a hanger to support that middle beam though. If I went with Option3 (link below), is it okay to hang joists off a single 2x10 ledger suspended between the foundation and post like I show? There will also be a set of stairs (only 2 steps) on the opposite side.
https://redirect.viglink.com/?format...on3.png%2Ffile
 
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Old 02-27-19, 08:42 AM
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The 2x10 from foundation to post should be doubled. Local code/inspector may want entire length doubled.

If you are concerned about hanging the beam on the foundation you could add a 2x6 or 4x6 "post" below the hanger anchored flat to the foundation for support if the hanger comes loose. ("Belt & suspenders" application--probably would never happen.)

If you are concerned about the beam pulling away from the foundation you could add a couple of "L" brackets on the side of the beam attached to the foundation with anchors.
 
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Old 02-27-19, 08:57 AM
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The 2x10 from foundation to post should be doubled. Local code/inspector may want entire length doubled.
That should be fine. Do they make wedge anchors long enough for that, or would I need to go the epoxy and threaded rod route?

If you are concerned about hanging the beam on the foundation you could add a 2x6 or 4x6 "post" below the hanger anchored flat to the foundation for support if the hanger comes loose. ("Belt & suspenders" application--probably would never happen.)
That's a good idea.

If you are concerned about the beam pulling away from the foundation you could add a couple of "L" brackets on the side of the beam attached to the foundation with anchors.
Could I also use a deck tension tie (DTT)?

I think I'd probably just go with one of the other options (beams parallel to rear of house) rather than do all these extra steps to hang that beam.
 
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Old 02-27-19, 09:27 AM
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You might have to go up to a 3/4 inch for longer length. https://www.homedepot.com/p/Simpson-...E&gclsrc=aw.ds

If you are using the shorter ledger you could overlap it beyond one of the anchor locations on the longer ledger and use lag screws to fasten the shorter to the longer at the foundation end.

Could I also use a deck tension tie (DTT)?
I would use something in a heavier gauge like 3/16 or 1/4 inch steel. I don't see any in the big box store sites. I have seen such items for boat docks in a supply store where I vacation.

BTW: This article https://www.decks.com/how-to/26/ledg...lid-concrete-fabout ledgers on concrete had a comment:
Here's the big problem with this: the joist hangers you use to attach the joists to the ledger almost universally call for 3" 10d or 3" 16d sinker nails, with the idea that you drives through the ledger and into the rim joist of the house for enough resistance to pullout. If you have concrete behind your single ledger, you are limited to 1.5" long nails on the face of the joist hangers. You can substitute approved structural screws like Simpson Titan HDs and that will get you a bit more pullout resistance, but in the end you will not be to code. You really have to do a double thick ledger against concrete.
 
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Old 02-27-19, 09:42 AM
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Here's the big problem with this: the joist hangers you use to attach the joists to the ledger almost universally call for 3" 10d or 3" 16d sinker nails, with the idea that you drives through the ledger and into the rim joist of the house for enough resistance to pullout.
I question the accuracy of this statement. I've never heard of this. AFAIK, it's 1-1/2" fasteners through the flanges and 3"(maybe 3-1/2") through the sides if the fasteners are driven at an angle. No fasteners should penetrate through the back of the board. The deck plans provided by my county state: "Joist hangers shall be fastened to the ledger board using its manufacturer's recommended screws."
 
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Old 02-27-19, 10:34 AM
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That was just a comment that someone posted in October 2017 that I came across while researching longer anchors.

Seems like a 3 inch nail would penetrate a 1.5 inch joist even if driven at an angle.

Manufacturer's recommendation is the way to go.
 
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Old 02-27-19, 02:10 PM
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I believe I have one other option, but it would require me to have a couple steps at the door, and it would block off a foundation window (not as if any light would make it in after the deck is built over it anyhow). This would be a non-freestanding deck supported by a ledgers on both rear-facing walls. I would put a platform outside the door with one step to get me down to a level where the ledgers could be secured to the foundation wall. I kind of wanted the deck up higher and the landing would take up some valuable space (since the deck is already so small), so I guess it will come down to cost savings. I'm not sure if it will cost much less omitting one beam and three posts, two of which need to be dug down to the house footing 6 feet below grade. I'd have to switch to 2x10 joists, which is fine.

https://www.mediafire.com/view/7a2j1...edger.jpg/file
 
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Old 02-27-19, 02:38 PM
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Sounds like too much compromise to me.

Those long spans may be acceptable but they might also be springy.

If ledgers can be attached to the lower foundation wall, why not a "post" attached low that supports a beam above? Eliminates the need to dig footers near the house.
 
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Old 02-28-19, 09:58 AM
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Are you doing this project yourself or hiring a contractor?
I may be doing it myself...first estimate came back today at a cost of $65/sq ft. I was outraged. This is a pressure treated deck. No composite anything. I estimated the cost of materials down to the nut/bolt and it came out to $12/sq ft, so $43/sq ft labor only? Come on.
 
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