building a low floating deck

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Old 05-31-16, 01:11 PM
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building a low floating deck

my back door is about 8" above grade. i'd like to put in a small 10'x10' deck. i don't really want to dig holes or put in a ledger. deck blocks + joists would probably be too high. and i don't want to excavate any soil because my backyard is pretty much level, and if i remove soil it will gently slope against my foundation.

i was thinking about burying some PT 6x6 pieces in the ground (dig a 5.5" trench, put 2" of sand at the bottom) so that the tops of the 6x6 are about 2" above grade, spread 1" of crushed stone in between, and then toenail a bunch of PT 2x6s into the 6x6s. then put deck boards over that (1x6 or 2x6 i guess) with as much spacing as i can give them. and maybe a 2x6 perimeter board so that the bottom of the perimeter board is still 2" above grade.

my hope is that the crushed stone will dry a little faster than soil so the bottoms of the joists (still an inch above the stone) stay a little drier. and then spacing hopefully allows a lot of air flow underneath the deck.

does this sound reasonable given the constraints of my backyard (no excavating!)

also if/when the deck moves around after winter, what's the easiest way to re-level the 6x6s at the bottom?
 
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Old 05-31-16, 01:18 PM
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Welcome to the forums.

Any way to convince you to do a patio instead?
 
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Old 05-31-16, 04:47 PM
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My vote would be for concrete or a paver patio. Wood, even pressure treated with ground contact like that will have a limited life. If you are in a coastal area where lumber treated to a higher content is readily available then it might last a while but most everywhere else 2"x lumber is only treated for above ground use. While you may technically keep the 2"x lumber above grade without proper air circulation below it will be just as bad.
 
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Old 06-01-16, 09:19 AM
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thank you both for your response. i greatly prefer the look of wood to concrete/pavers, which is why i was hoping to do a deck. maybe i can find a product that looks like wood but won't rot when in contact with the ground.

so, to be clear, an inch between grade (crushed stone) and the bottom of the joist isn't sufficient? i know code usually wants to see 8"+, so i guess water has a way of finding it's way up.
 
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Old 06-01-16, 10:37 AM
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It isn't so much standing water but rather what moisture collects under the deck [including framing] doesn't have enough ventilation to help it dry out quicker. The longer it stays damp beneath the deck, the more moisture the wood will absorb = shorter life for the wood.
 
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Old 06-01-16, 11:26 AM
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Moisture comes up from the ground all the time and you need airflow under the wood to mitigate this. 1" is not sufficient.
 
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