Help with Deck Structural Design

570 Views 13 Replies 6 Participants Last post by Bret86844, May 13, 2020

Bret86844

Discussion Starter · May 13, 2020

Hey all, I'm putting plans together to build a deck out back of my house. I plan to do a floating design. The struggle I'm having is how to support it because there is an existing patio. It's constructed with a 6" concrete slab (yes, 6") with brick on top, grouted in. My thought is to use deck blocks on top of the concrete, and buried concrete piers where it extended over the yard. Any thoughts on this design?

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huesmann

· #2 · May 13, 2020

"Floating" as in freestanding?

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Bret86844

Discussion Starter · #3 · May 13, 2020

huesmann said:
"Floating" as in freestanding?

Correct, no ledger board connection to the house. The house overhangs the ground by a couple feet and per design guidelines, you can't connect the deck to the house anyways.

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Nealtw

· #4 · May 13, 2020

I made a few changes. :wink2:

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Bret86844

Discussion Starter · #5 · May 13, 2020

Nealtw said:
I made a few changes. :wink2:

Thanks for the comments! What do you mean by 2x4 blocks? Like this?

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Nealtw

· #6 · May 13, 2020

Bret86844 said:
Thanks for the comments! What do you mean by 2x4 blocks? Like this?

Yes, but the only have to be 2x4 the deck above holds the top straight

You only need one row in a 14 ft span but I would go 2 rows just because.

13 feet should be okay with 2x10s the cantilevers don't count.

9 ft for double 2x10 beams should be good.

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SPS-1

· #7 · May 13, 2020

Nealtw said:
Yes, but the only have to be 2x4 the deck above holds the top straight

Then flush with top, not bottom, right ?

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Nealtw

· #8 · May 13, 2020

SPS-1 said:
Then flush with top, not bottom, right ?

no the top is held on layout with the decking these things hold the bottom from rolling over. Just like bridging, it's about keeping the bottom in line.

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3onthetree

· #9 · May 13, 2020

Nealtw said:
Yes, but the only have to be 2x4 the deck above holds the top straight

9 ft for double 2x10 beams should be good.

That (2) 2x10 outer beam where joists above span 13' is only good for about a 6'-8" beam span.

I think the changes you made were trying to eliminate multiple posts on the slab so when it settles you'll have uniform movement/or can shim later as necessary? Also, putting the flat 2x4 blocking at the bottom edge allows lots of water to sit on them?

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Nealtw

· #10 · May 13, 2020 (Edited)

3onthetree said:
That (2) 2x10 outer beam where joists above span 13' is only good for about a 6'-8" beam span.

I think the changes you made were trying to eliminate multiple posts on the slab so when it settles you'll have uniform movement/or can shim later as necessary? Also, putting the flat 2x4 blocking at the bottom edge allows lots of water to sit on them?

Flush not flat. :wink2:
We do 2 ply 10 and 12 ft all the time but he could go to 3 ply or move up to 2x12.

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3onthetree

· #11 · May 13, 2020

Nealtw said:
Flush not flat.

Thanks, pictured it like interior bridging and inserted words in my head.

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Nealtw

· #12 · May 13, 2020

3onthetree said:
Thanks, pictured it like interior bridging and inserted words in my head.

Inside they are often flat under duct work. :wink2:

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House Designer

· #13 · May 13, 2020

You are in Cleveland (so am I) where structures are subject to frost heave. Either make all of the footings to frost depth, or don't make any of them to frost depth. If you mix floating footings with frost footings, the deck will move and lean during the winter, and nails will pull and straps may tear.
I would pour tiny 12" x 12" x 6" thick concrete patios at the outboard end of the deck, and then rest deck blocks on them. Then the entire deck will move uniformly with frost heave, and all will be good.

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Bret86844

Discussion Starter · #14 · May 13, 2020

House Designer said:
You are in Cleveland (so am I) where structures are subject to frost heave. Either make all of the footings to frost depth, or don't make any of them to frost depth. If you mix floating footings with frost footings, the deck will move and lean during the winter, and nails will pull and straps may tear.
I would pour tiny 12" x 12" x 6" thick concrete patios at the outboard end of the deck, and then rest deck blocks on them. Then the entire deck will move uniformly with frost heave, and all will be good.

Yeah, that's probably a good idea. It seems weird having two different types of supports.

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