12'x20' Low Elevation Deck Questions

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Old 08-25-15, 08:50 PM
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12'x20' Low Elevation Deck Questions

Hi All,

I've been watching so many videos, searched through endless sites, tried deck designers, etc..., so now I wanted to see what everyone here thinks of this proposed design. I've never done anything like this before but it doesn't appear to be that difficult to do. I just wanted to make sure I'm not using too much materials, and I'm using the correct type of materials, etc...

I'm looking at doing a 12'x20' free-standing deck. I live in South Florida. My house is concrete block, so I don't want to do a ledger board because it seems like I would need to use special bolts/screws for the hollow blocks, such as $40 anchor or sheath bolts/screws. It's not a very high deck, maybe about 1' or 1' 1/2" off the ground.

On the right and left side of the deck (the 20' sides), I will have the support beams extend 2' past the support posts. On the bottom and top side of the deck (the 12' sides), I will have the joists extend 1' past the support posts. The support posts will be 4"x4" and will be 2' in the ground, which will have quikrete poured in it, just like installing a fence post.

Are the joists and support beams being 2"x6" OK for the possible loads? Am I missing anything? Do I need to move the support post closer to each other or maybe required another row of support posts?

Let me know if there are any questions, I hope I put enough information in this post.

Thanks!

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Old 08-25-15, 10:32 PM
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The posts should set on top of the concrete footings not go into the ground like a fence post.
 
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Old 08-26-15, 04:35 AM
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9' is encroaching on the limit of the 2x6 span. I would opt for 2x8 joisting considering your overall span. Free standing is always the way to go if possible. Your low deck will be ideal for this. Consider the air flow under the deck, as it needs to breathe. Your 12" may prove not to be adequate enough. Are you limited by doorways or other obstructions?

What Pulpo said about the posts is spot on. No burying of posts (except for fences). They will rot out too quickly for a permanent fixture such as a deck. Here is a definitive article you should read and digest before starting your campaign. It will give you the information to build a good, substantial deck. Of course, please post here if you need help as well, as there are several pros that can help with your needs.

http://www.awc.org/pdf/codes-standar...Guide-1405.pdf
 
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Old 08-26-15, 06:11 AM
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Hi guys,

Thanks for the info so quickly. Yeah, I was weighing between the 2x6 and 2x8 due to the distance between support posts. I'll look into doing the 2x8 then. The only obstructions are the two sides with walls, the other two sides are completely unblocked.

For the posts, if I set them on top of concrete, would you then put something like gravel around the posts to fill up the empty space around the posts? Or just through the dirt back in?

I'll take a look at that guide, chandler.

Thanks!
 
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Old 08-26-15, 06:48 AM
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The concrete should extend above the ground and you embed a post anchor (or threaded rod) in it while concrete is wet. The post fastens to the anchor once concrete is set. You would use a sonotube or the like as a form for the footing. By pouring the footers a little higher you may even be able to dispense with the posts and rest a doubled 2x8 on a beam anchor (instead of a post anchor) right on the footers. But that will mean getting the heights of the footings exactly right. That's not that hard when you use sonotubes because you just set the forms to be level and plumb before you pour the concrete. Chandler is right suggesting you use 2x8s.

You're not planning on a hot tub or other heavy concentrated load are you? That would require beefier framing. Good luck!
 
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Old 08-26-15, 06:57 AM
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CarbideTipped,

I don't plan on adding a hot tub or anything like that, just some chairs and a table for people to hang out on is all.

So no one would set posts in the ground? OK, I guess I'll have to re-think that. Darn you Lowe's for misleading me! Hah.
 
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Old 08-26-15, 07:00 AM
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Bad advice from Lowes?? Oh that never happens
 
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Old 08-26-15, 07:52 AM
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Deck

Your cantilever design will require the joists running lengthwise to set on top of the yellow beams running in the 12 foot direction.

2x8 beams and joists plus 1 inch thick deck boards will add up to 16 inches of vertical thickness from the bottom of the beams to the top of the floor boards.
 
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Old 08-26-15, 08:10 AM
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Hi Wirepuller38,

Thanks for responding, but excuse my ignorance, were you commenting on something I should change?

It seems like out of all of this, my only two outstanding issues are:
1) How best to support it (post on concrete in ground, metal bracket, etc..), and
2) How best to stagger the 10' joists for the 20' width of the deck. Should I use 12' joists just in case and let them overlap?
 
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Old 08-26-15, 02:38 PM
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maybe about 1' or 1' 1/2" off the ground.
Not stealing Ken's thunder, but I think he may have been thinking of the height you quoted. It will obviously change with larger joists, etc. He too probably was worried about obstructions with the newer height, such as doors, etc.
 
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Old 08-26-15, 02:57 PM
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Deck Height

It's not a very high deck, maybe about 1' or 1' 1/2" off the ground.
Larry is correct. I was thinking about the finished height in relation to any doorways adjacent to the deck. Do you have 16 inches of vertical distance from the thresh hold to the ground?
 
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