Freestanding / Floating Deck questions about codes and Deck Beam Spans


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Old 04-08-18, 10:38 PM
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Freestanding / Floating Deck questions about codes and Deck Beam Spans

I am planning to pour a large concrete patio on the back of my house in the a couple of weeks in Florida. I need to know where I have to put the footers for a future second story freestanding deck. I have included model pictures of what I am planning to do. First the pictures include no bracing, assume I will add that if all other parts check out. I want to use waterproof aluminum decking with boards perpendicular to the house in order to shed water. That is why the joists are running parallel to house. The Beams are 3x12 pressure treated pine, which I believe the is the largest you can go before moving to an engineered beam or metal. the posts are 6x6. I want to do a 13x40 deck with no posts under center to allow for screened in room with pool/ping pong. I just don't know if I can span as far as I want between the posts next to the house and the and post on the perimeter. I can not attach the house because have a small 1ft cantilever coming from the second story. Will my plan be code compliment. If not how can I make it so. Also Assume I am attaching the beams to the posts and the posts to the beams using Strong Tie Brackets.
3 2x12s do not sit cleanly on a 6x5 , what do I do with extra inch on top of the beam? Any help would be greatly appreciated.
 
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Old 04-09-18, 04:52 AM
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You should not have any trouble with span distances with so many columns. As shown you'll only have 13' and 8' spans which are well within the scope of traditional lumber. You could easily drop a column or two and still be in good shape with your spans. As for where your footers need to be located... they will need to be under your columns wherever they end up being.

Since this is a two part project I would get your permits based on the completed structure. Also, find out how long a project can pause without having to acquire a new permit. Many areas give you a year. What you don't want is to get your patio poured then try to do the deck in 3 or 5 years only to find that they have changed the codes an your plan will no longer work. I would build this project so you can complete everything within the first/original permit so you don't have surprises or changing codes to worry about.
 
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Old 04-09-18, 05:38 AM
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Your deck is missing the diagonal bracing. See figure 10 in the DCA6... http://www.awc.org/pdf/codes-standar...Guide-1405.pdf

You will also need tie downs and lateral load devices. Plus if you are in Florida there may be additional requirements we don't know about. Consult with your local building inspector before you begin. They may have a flyer that can help you plan.
 
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Old 04-09-18, 07:28 AM
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Yes I know I will need the diagonal bracing. I just did not include it because my 3D modelling skills are not the best. As for the tie downs and lateral load devices, could you be more specific? I went over the PDF but I have not come across anyone using them.
 
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Old 04-09-18, 08:20 AM
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Figure 12... your tie downs will need to be embedded in concrete.

Figure 22, 23... your lateral load devices will need to go on your beams.
 
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Old 04-09-18, 08:37 AM
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Yes of course I will have post anchors set in the concrete during the pour. But I still fail to see how you use lateral load devices on a freestanding deck that is not attached to the house. Also I am guessing the rim joist should not be placed on top of the post like I have it, correct?
 
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Old 04-09-18, 09:12 AM
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Read page 17. Its pretty clear.
 
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Old 04-09-18, 11:01 AM
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I have read it multiple times to no avail. I think it is referring to non-ledger decks that still have an attachment to the house. My deck is freestanding with no attachment and 1 inch away from the house, so there is no way to add tensioners without skewing the deck. House is stucco btw. I am more more concerned with my beam span. Is my 3 2x12 enough to span over 12 feet, or is it even overkill? Should I look at 2x10s?
 
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Old 04-09-18, 03:46 PM
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Your span is fine. Three 2x10s as the beam would be over spanned at 11' 6" according to table R507.6.

If you are doing freestanding, you can still use the lateral load devices if you block the space where the lateral load devices go. It makes for a more solid structure. I would think you would want to block and flash the space so that rain does not enter between your roof and wall.

If you do not want to do that, then you must follow R507.10.1, and use diagonal blocking in both directions to give the structure stability.

And like I said, since you are in Florida, they may have higher standards that we don't know about, since you are in a hurricane prone area. You will want to verify your plans will be approved by your local building dept.
 
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Old 04-10-18, 04:12 AM
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I thought since I had a joist span over 8 feet I might be subject to the 10 feet beam span limits. But I am guessing you are saying that I am subject to the 8 feet column UNTIL my joists reach 10 or longer. Correct? I will try to update the model with knee braces. Also the outer joist that runs along the entire front edge of the desk. Should it be resting on the top of the posts and take away from the area the triple 2x12's could take up on top of the 6x6 post,? Or should it just be anchored to the triple beams edge and not directly above the post? I was thinking of using 4x4s for knee braces. I know how they would attach to the post but not sure what is the best way to anchor them to the triple 2x12 beam. I see some Simpson's angle brackets but not sure they would work unless I use 6x6 for knee braces instead.
 
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Old 04-10-18, 05:51 AM
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Yes, and your beams should rest fully on the posts... it's the only way your post connector bracket will work. As mentioned in R507.10.1, Bracing can be 2x4 on the outside, attached with 1/2" through bolts.
 
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Old 04-10-18, 09:09 AM
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Ok, thanks so much for all of your help. Is there a preferred method/bracket of attaching that outer joist to the beam if it is not sitting on the post? I am guessing just right angle brackets? If so is there a specific bracket? Since I would like to save as much money as possible, what is the smallest joists you think I can go with? Looking at the chart it looks like I would be good with 2x8s with 16oc.
 
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Old 04-10-18, 09:13 AM
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Also if the joist is sitting past the post, I am thinking it would conflict with one of the outside knee braces.
 
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Old 04-10-18, 09:27 AM
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2x8s should be fine. I would probably add two layers of treated 1/2" or 1 layer of treated 3/4 to the beam sandwich (whatever it takes to make it the full 5 1/2) so that you can use 5.5x5.5 post caps. (Like Simpson BC6) The rim in front and back should go between beams and you can reinforce it on the interior side only with an l-angle (Like a Simpson L70.)

If you want a continuous rim in front just for looks, put it on afterward.
 

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Old 04-10-18, 02:23 PM
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Ok that all makes sense. As for railing posts. I rather they be attached to the inner edge and sandwiched between two joists. Except where they would be directly over the beams. Can railing posts be directly attached to beams using a Simpson bracket? I don't think I have ever seen it done.
 
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Old 04-10-18, 07:41 PM
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You could use a pair of Simpson Strong-Tie RPBZ Retrofit Post Bases on the corners or anywhere else a post is directly over a beam.

Hangers: Simpson Strong-Tie RPBZ Retrofit Post Base - Contractor Supply Magazine
 
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Old 04-18-18, 07:03 PM
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Ok, I added the cross bracing like your suggested. However I ran into a number of issues. The front braces are good but the back and perpendicular ones are not. See pics. The cross braces along the house won't work with the perpendicular ones unless I put the braces on the other side of the posts, which would bring the posts further out from the house, which I would like to avoid. I think I rather use 4x4 or 6x6 as braces for those like here: https://inspectapedia.com/BestPracti...gure4-12ss.jpg Although I would use 1 or 2 carriage bolts to attach the the bottom of the brace. I am not sure how to attached the top of the 4x4 to the three 2x12 ply beams properly. On the front and sides I would like if none of the cross bracing entered to the space between the posts. This is so I could easily install drop down screens like this: https://www.pinterest.com/pin/413768284492895658/
 
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