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mbturner
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# Posted: 8 Mar 2026 09:22pm
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Hi,
I have a small bunkie in the back of my property. I need to attach a deck this spring. The foundation framing on the front is two 2x8's screwed together. Can I just attach my decks joist hangers right to those double 2x8's? I dont want to do a floating deck as there is quite a bit of slope (cant really tell from this pic). Also the foundation is insulated and all sealed up so I cannot put anything into the joists from the backside either. Thank you!
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gcrank1
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# Posted: 9 Mar 2026 09:42am
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Ive built attached decks at home and 3 cabin decks. The cabin decks have their own block 'floating foundation' and had NO trouble. One was on a bit of slope and still fine after 30+ years. Compared to a cabin decks are light. IF you ever had to relevel it would be easy.
To me being able to move a deck has been a good thing.
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Brettny
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# Posted: 9 Mar 2026 10:06am
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Yes that sounds fine with the hangers.
Those screw post foundations don't make the whole building wiggle?
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DRP
Member
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# Posted: 11 Mar 2026 10:53am
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Flash it properly to keep water from rotting out the floor framing (what you called the foundation). The foundation is those pier blocks and screw jacks. As Brettny's gut told him, that is prohibited in most codes.
Then the "correct" way is to check the strength to the double 2x8's to carry not only the cabin but about half the deck load. The cabin ledger will carry half the deck load, the outboard pier and beam will carry the other half of the deck load.
Study this deck guide, it has been adopted by many jurisdictions. fig 14 shows one flashing detail, I have other sketches if that is not clear.
https://web-media.awc.org/wp-content/uploads/2022/02/17210514/AWC-DCA62015-DeckGuide- 1804.pdf
The deck to floor system connection if done improperly causes a lot of grief. I've worked on homes where unflashed decks rotted out the floor system of the house, major repair, make sure you understand how to protect the floor framing.
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gcrank1
Member
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# Posted: 11 Mar 2026 11:22am
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That is another reason I like my cabin decks spaced out from the cabin a bit and on their own supports.
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DRP
Member
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# Posted: 11 Mar 2026 01:04pm
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Here's another good resource from Dr Woeste at VT. He was one of the people responsible for the design guide above. Being the carpenter in one of his classes full of inspectors and engineers, it was my nailing and notions tested to failure during the lab session. A little humbling 
https://vbcoa.org/wp-content/uploads/2020/04/Deck-Inspection-Resources-2020-4-16.pdf
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travellerw
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# Posted: 11 Mar 2026 01:19pm
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Sounds like a great opportunity for screw piles. There are even ones you can drive by hand nowadays.
Put the deck on screw piles and keep it about 2 inches away from the building so the 2 are isolated.
That would be my plan!
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gcrank1
Member
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# Posted: 11 Mar 2026 02:01pm - Edited by: gcrank1
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How big is this proposed deck?
Fwiw, I have two 9' x 12' decks, each on a stand of 3 'blocks' under the long sides. IF I ever need to I can add in another stand for 4 on each side, doubt I'll need to, they are just decks about 20" above grade.
1st ground block a solid silo stave for a big footprint, the rest centered stacked blocks to level at desired height.
Guess I could put in some anchors to cinch to ground but I'll take my chances that a blow big enough to take 'em wont happen. IF it does those 2 decks will be low on my list of damages.
I could have used short posts and an pair of under-beams too, I had the blocks.
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philpom
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# Posted: 12 Mar 2026 07:11pm
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Mine is attached directly but has a full set of legs so technically self supporting. Just make sure you give a slight slope away from your building so water runs away. A 1" drop in deck height compared to the cabin floor is also a good idea. If you aren't going to cover the deck, at least put a real good overhang above the door. It's nice to have a little dry spot right out the door.
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DRP
Member
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# Posted: 12 Mar 2026 08:55pm - Edited by: DRP
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I did the same thing. We have a continuous strip footing that projects out from the crawlspace wall about 6". I ran 6x6 posts from that projection up to the underside of the deck ledger at each end and the middle of the ledger.
Self-supporting and spaced off the building is good. If a roof or structure from the building is supported by the deck, then it needs to be tied firmly to the building... you then have locations that must remain exact. You can bolt a gap with washers or pipe spacers for the lateral, wind, seismic or line dancing load, and the posts pick up the vertical, gravity, load.
another minor variant on philpom's deck drop comment. I put the deck top of floor 1-1/2" below the subfloor of the house. Flash, install door and deck with decking and slide a treated 2x4 under the projecting door threshold. I take my power plane and chamfer and slope the projecting edges.. It's the same concept, well, a ripping of decking under the threshold would make for a 1" drop.
I drew the attached sketchup for the building inspector on a job a few years ago. The dark brown layer flashes the house rim, the double 2x8's, from the treated, seriously wet, deck framing. If there is a gap it is outside of that flashing. The light brown counterflashing is tucked under the siding and housewrap and laps over the deck ledger shedding any wall or deck water out over the ledger.
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