Unusual Cantilever?

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Old 05-24-14, 11:09 PM
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Unusual Cantilever?

So I bought this little cabin in Alaska and I'm making some repairs and learning a whole lot in the process. Recently I've been putting up a rail on the outer edge of the deck and am curious as to why the builder stopped where he did. The cabin was never completed so I am unsure if the point at which he stopped was deliberate or not. I am including pictures as I am certain they will do a better job showing the situation, although I will try to explain it as best I can.

I would like, if possible to extend the deck out the remainder of the length of the deck beams. The joists run parallel to the cabin front. The cabin itself is built on post/beam foundation. The one photo I have of the underside is of under the structure itself, not under the deck. Two deck beams stick out from the front of the deck about 4 feet. The beam on the edge of the deck is supported on it's end by a post, so there is no worry about cantilever there. The other beam however is already supporting the deck with about 2' of cantilever and there is another 4' sticking out. I know this would generally be an issue, but because of the oddity of the construction I am posting it here in hopes someone might shine some light on what is going on here. The beams are 3"x12" and the posts are creosoted 8"x8"s with a few 6"x6"s.Name:  cab 230.jpg
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Old 05-25-14, 05:12 AM
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Welcome to the forums!

I don't know what the original plans where but that isn't how you cantilever a structure. For a cantilever to work each joist must be cantilever out - not just the ones on the sides. I suspect your best bet is to cut those 2 joists off..... but I'm a painter, the carpenters should be along later.
 
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Old 05-25-14, 05:52 AM
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I agree with Marksr. Even if the ideal plan was to extend the deck, why enclose those trees in it? They will grow, die, fall, or cause other damage to the deck. Cut the ends off flush.
 
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Old 05-25-14, 10:54 AM
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Well, I have no problem cutting down a tree or two and in this particular case I'd only be cutting down the one tree between the two beams. Although the deck is built on three 3"x12" beams, only two protrude from the front of the deck and that is the section I would be extending. Of those two beams only one is not supported at its end. The protruding beam at the edge of the deck is supported at its end which creates a problem should I want to cut those beams flush with the existing edge of the deck. And of course the unsupported beam creates a problem should I want to extend the deck.
 
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Old 05-25-14, 11:06 AM
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In order to utilize those cantilevered joists you'd need to double them up so you could hang joists off of them ... and of course support the unsupported end. Not sure of the distance but you'd probably also need a support beam in the middle.
 
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Old 05-25-14, 11:45 AM
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Thanks for the info Mark,

I guess I'm unsure though why I'd have to double them up and add a support beam? The rest of the deck lacks these features. The beams (bearers) are 3"x12". The joists in this deck run parallel to face of the house. I'd assumed all I'd have to do is continue building in the same fashion. Basically build the deck box (joists and decking) right on top of these two protruding beams.
 
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Old 05-25-14, 11:54 AM
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I have to use bifocals nowadays, but I see a big old honkin' post supporting the beam just under the deck. you would likewise have to support what is now cantilevered. The length of the cantilever is too long to leave unsupported.
 
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Old 05-25-14, 12:30 PM
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Hmmm, how about diagonal bracing?
 
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Old 05-25-14, 12:35 PM
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Diagonal in which direction, and what will support the bases of the diagonals? Wouldn't it be just as easy to dig footings and put in posts?
 
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Old 05-25-14, 06:06 PM
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So a question or two about posts and footings:

The soil in this particular area is about 6-12" deep before turning into volcanic ash which it remains until finally turning into solid rock. I suspect in the area I'd need to erect the post there is no more than a foot or two total of soil/ash before reaching the rock.

What sort of special considerations should I make for installing in rock? Do I need fasteners or can I simply set it on top.

Also, the original builder used 8"x8" creosote treated posts. I cannot take a measurement right now as I am not near the deck, but I believe that this support post will be between 10-15'. Does it need to be a creosote 8"x8"? And are there any problems with a support this high?

Thanks for all the info.
 
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Old 05-26-14, 04:55 AM
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Creosote was outlawed 20+ yrs ago, could they have used RR ties? I know you can get 6x6 PT, not sure if you can 8x8 PT. The main thing with tall posts is to make sure they are stable - might need cross bracing. I don't know about your footer requirements.
 
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Old 05-26-14, 12:45 PM
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It still legal and available in Alaska. My place was built less than
seven years ago. I'm not sure you can just go to the lumber yard and pick it up as a DIY guy, but if you're commercial it's fairly easy to come by. In any case I agree, it would be just as easy to pick up some PT, but it might stick out compared to whats already there.
 
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Old 05-26-14, 01:07 PM
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Locally we can buy stain that mimics the look of creosote. While it's never fun to apply, creosote has it's uses - wish we could still get it around here.
 
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