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Can anyone tell me whether I can cantilever a deck 29″ from the last beam? Or direct me to some tables. I haven’t been able to find any.
The deck joists: 2x8s on 16″ centers, 7’8″ from the ledger to the beam. And I want to cantilever the joists an additional 29″ from there. The decking will be 2×6 redwood. Intuitively, I think this should be fine, but I can find no info to back it up. Can anyone help?
On the same theme, how far can one hang 2×6 redwood decking over the end of the rim joist? I have a spot where I want to go 11″, but that sounds a bit iffy.
Help appreciated
Replies
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This cantilever should be fine for your joists if you use #2 redwood or better. You could cantilever the decking 11" but I think it will look funny.
*the rule of thumb I read somewhere (I know, not very persuasive) was that you could cantilever up to 1/3 of the main span. Would like to hear a more scientific explanation. 29" sounds a bit far without support, but I'm sure Mike knows what he's talking about. At some point you do have to worry about uplift forces at the ledger -- say your whole family decided to assemble at the edge of the cantilever for a group photo. Well, maybe you don't like them anyway.11" overhang sounds too far -- at the very least the boards are going to warp up and down and make it look rather odd. What will support the railing? Perhaps if you ran a board perpendicular near the ends to make them move as one?
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I almost feel guilty saying it on this site, but there's an article and table of calculations for this in this months' Journal of Light Construction
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Actually I pluged those figures into a computer program. I used 60 psf live load and a 10 psf dead load. I plugged the decking in too. I only thought how wierd it would look, so I forgot all about the warping which would be terrible.
*Which program? And why don't they plug in a "warp alert"?!? :)
*I would avoid using a table for cantilevers since there is no counterbalance weight in the equation. Normally we don't cantilever any more than 12" on a deck past the beam, (2x8, 16's), to avoid diving board kind of action. I'm sorry to say that you will not like the result of 29" overhang,(what I would call it). Also to overhang the decking 11" would be acceptable as long as no-one is to walk on it and you connect the boards with some kind of trim. To extend to that overhang I would run a baseboard, (2x6), as a kind of reverse ledger. Hurricane clips to connect to the beam. And up the joist size to 2x12, and further lower the spacing to about 12". Double up the rim joists as well, and add blocking mid span. Now since you have increased the load on the footings they should be a little larger as well. Just a guess though...! I must say, congrats for having the nads to push the envelope.
*The program is Maxbeam. There is a companion program for shear called Maxquake/wind. They are a little pricey if you don't have a real need for them. I treated the decking as joists, 1.5" deep x 3.5" wide,4" oc, with a 16" span and 11" cantilever. The program accepted this, but knows nothing of warping.
*I would love to see the plans for this one. Even a sketch would do...just post it on here.Pete Draganic
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Thanks for the thoughts...it's a unique situation. No "envelope pushing" intended. No accesss to a scanner, so I'll try to describe:
the deck goes from a house to the cinderblock wall (owned by the other guy) at the property line. Years ago, someone poured a cement wall with slots for 2x8s on 16" centers, clearly with a deck in mind.
So the deck goes from a ledger lag-screwed on the house --- joists on joist hangers at the ledger, through the cement wall with slots...this is the last support, at 7'8" from the house. The 29" cantilever is the remaining distance to the cinderblock wall. I was trying to avoid putting a ledger on that wall since A) I don't own it, and B) How the heck can you make a decent attachment to cinder block? (suggestions here appreciated).
Saftey is not an issue since the whole thing is only 18" off the ground. The cantilevered end abuts a chainlink fence set in the top of the cinderblock wall. So there will be a "privacy screen" but no railing.
The part where I wanted to hang the deck boards off the last joist 11" is dictated by the shape of the wall and the location of the last joist slot in the pre-existing concrete...an odd solution for an odd space.
So my concerns are mostly about "bounciness" of both the cantilevered joists and the 11" of deck boards overhanging the rim joist, though I do wonder about the uplift on the ledger edge of the joists.
ml
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That must be why they put those "extra" nail holes in the joist hanger brackets! 8-)
-Rob
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To resolve the warping problem the 11" cantilever on the redwood 2x6's you can attach a 2x4 or a 2x6 plate to the bottom of the deck perpendicular to the deck end maybe 4' back from the edge. What this does is "stitches" the deck edges together. All the decking would have to warp in the same direction to percieve any warpage.
This has worked fine for me in the past if the deck if fairly low to ground so you do not see the plate.
The plate needs to be screwed to the deck boards rather than nailing to keep from bouncing your other fasteners out of the board. Also screws alleviate the bouncing of the deck while you are trying to nail it
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i'd probably put in a couple more posts near the end with another beam to rest the joists on about a foot from the end, then you should have no uplift or overhang problem. also would probably run another small ledger along the house for the unsupported deck boards if you can or put a small beam arrangement below them to support that decking overhang. I usually dont attach to the house at all so i dont have moisture problems. Also, there is no guarantee that that wall will not sink, since you dont really know how it was built. (concrete wall with notches for joists)I guess it might depend on your climate too.
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How about angle braces up/out from your concrete wall to the outer ends of the joists? Might be a job to drill for anchors, but it would fix the bounce.
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Mike,
Would you know who the company is that sells MAXQUAKE and MAXWIND. I have not been able to find it.
Thanks
Darrell
*884 Portola Road, Portola Valley, CA 94028Fax 1-800-968-ARCH (1-800-968-2724)or call Archforms, LTD 1-800-958-ARCH (1-800-958-2724)http://www.gry.com/arch/index.html
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Can anyone tell me whether I can cantilever a deck 29" from the last beam? Or direct me to some tables. I haven't been able to find any.
The deck joists: 2x8s on 16" centers, 7'8" from the ledger to the beam. And I want to cantilever the joists an additional 29" from there. The decking will be 2x6 redwood. Intuitively, I think this should be fine, but I can find no info to back it up. Can anyone help?
On the same theme, how far can one hang 2x6 redwood decking over the end of the rim joist? I have a spot where I want to go 11", but that sounds a bit iffy.
Help appreciated