Low deck strategies

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Old 07-18-05, 08:31 PM
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Low deck strategies

I will be replacing an old deck this summer. The deck will be 16' deep and 24' long (parallel to back of house). Current deck is a mish mash of half baked construction techniques.

This deck, at its highest point will only be 17" off the ground (ground to top of decking material). This is really only in one corner, the rest of the deck is right down on the ground pretty much. I'm trying to figure out the best strategy for joists, girders, posts etc for this deck.

Near as I can tell I'll need to go with a split two piece girder that sandwich's the posts, as opposed to setting the girder on top of the post. I hope this will let me get the girder, and subsequently the joists lower to the ground. If it turns out I can't get even a post plus the post anchor (planning on using cylinder with concrete and post anchor hardware) do I have to excavate all that sod/soil out and dig down below grade to set the post piers?

What about the 16' span from the ledger to the end of the deck, can I span that distance without putting in an intermediate girder?

On the two outside corners I'd like to round off, or square/angle off the deck such that people won't catch their legs on the 90 degree deck corner while walking on the path. How do I do this? Just set the girder back aways from the end of the deck? If I'm using the two piece girder strategy I can't really extend the joists beyond the girder to the 16' mark since they are not on top of the girder?

Hope some of this made sense...

Thanks
Wayne
 
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Old 07-22-05, 09:35 AM
jcs
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Originally Posted by Wayne02
Near as I can tell I'll need to go with a split two piece girder that sandwich's the posts, as opposed to setting the girder on top of the post. I hope this will let me get the girder, and subsequently the joists lower to the ground. If it turns out I can't get even a post plus the post anchor (planning on using cylinder with concrete and post anchor hardware) do I have to excavate all that sod/soil out and dig down below grade to set the post piers?
Hi Wayne,

Didn't see any replies to your message so I'll post what I know. Take what I say with a grain of salt, I'm bulding my first deck right now so I'm not a pro.

So it sounds like you're planning a flush beam design (joists & girder on same level) as opposed to a drop beam (joists sit on top of girder), since your deck is pretty low. So is mine, and I'm using a flush beam design as well. But if you're sandwiching the posts between 2x members that form the girder, and then your joists are attached to the girder by joist hangars, then only one of those 2x's on your outside girder is holding any load. The outer 2x isn't doing anything for you since the joists aren't distributing ther load onto it.

So you don't have enough room to use 6x6 posts and notch it to accept a built-up girder of two 2x's lag-bolted together? Or have the girder sit on top of the posts? Upon advice of my building inspector, I did the latter using some fairly expensive 12 gauge post-beam connectors (Strongtie). I used 6x6 posts and a triple-beam of 2x8's lag bolted together with 1/2" plywood spacers. A 3rd option is to pour your piers so that the girder can sit directly on top of the piers without any posts. This is tricky though -- you have to position and level your pier former tubes just right and you only have one chance to get it right.

One thing you don't want to do is have your pier-post connections below grade. They'll rot.

What about the 16' span from the ledger to the end of the deck, can I span that distance without putting in an intermediate girder?
No, you'd want to have a middle girder as well. You should consult the span tables to find out what lumber and spans to use.

On the two outside corners I'd like to round off, or square/angle off the deck such that people won't catch their legs on the 90 degree deck corner while walking on the path. How do I do this? Just set the girder back aways from the end of the deck? If I'm using the two piece girder strategy I can't really extend the joists beyond the girder to the 16' mark since they are not on top of the girder?
I can't think of a way of angling or rounding the corners with a flush-beam deck.
 
  #3  
Old 07-22-05, 10:54 AM
tahoe
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My husband and I just built a low deck last year but admittedly it wasn't as close to the ground as yours seems to be. That being said everything I read said that the best construction was with the joists on top of concrete posts, not attached to the side of the posts. While I know our town's code required 2 x 8 joists, maybe you could get away with using 2 x 6 to give yourself some room.

Regarding your 16' span, you should definately add an intermediate joist. Again, code in my town specified how far you would span before needing additional supports and I think it was in the neighborhood of 8 feet.

Good Luck
 
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