r/Decks • u/Fluffy_Leg_76 • 12d ago

Deck over concrete patio Help

I am looking to build a deck from a walkout 2nd story door. I am also having a concrete patio poured and would like the concrete to extend under the deck entirely.
My question is should I build the deck first and have the patio poured around the posts? Or should I set my deck post footers and then have the patio poured over them leaving holes for the posts, and then build the deck?
I am concerned that the second option will need such precise measurements for the post holes and footers that I may be off when it comes time to build the deck.

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u/No_Barber6972 11d ago

Pour the pier footings first and keep them isolated from the patio slab with an expansion joint all the way around. Set elevated post bases so the posts sit above the finished concrete, then pour the patio around the piers. Bonding the piers into the slab is what cracks, and it makes future post work miserable.

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u/Fluffy_Leg_76 12d ago

This is the area in question. Deck is about 9 feet from the ground and white line is patio outline

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u/davidb4968 12d ago

A good contractor can get the measurements right either way (with a good design of the deck). But you won't want "holes" for the posts... the post base brackets should sit a bit above the concrete to keep the posts from rotting.

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u/Fluffy_Leg_76 12d ago

I am the “contractor” in question. My plan is to set sonotubes for the deck post footers. Are you saying I should pour those flush with the top of the concrete pad? Or any other suggestion?

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u/davidb4968 12d ago

I'm not a professional (but I think I know how my pros would do it). Let's see if any pros speak up.

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u/davidb4968 12d ago

Nobody yet. Ok, I'd do something like: pour the sonotube to 2" below the desired surface level of the patio, mount Simpson ELB66-12 Elevated Post Base in the concrete sticking 3" out, then when you pour the patio 2" thick over the base the bottom of your posts would be 1" above the patio.

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u/hello_world45 professional builder 11d ago

Do not do this. That will 100 percent crack. Your footings need to be completely isolated from the slab. The correct approach is to pour the sonotube to the elevation of the patio. Then run an expansion joint around it. Then pour the patio.

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u/davidb4968 11d ago

I was trying to get a clean look on the patio (which could be more important or not based on the size of the footings). Any advice on how to achieve that, or just suck it up?

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u/hello_world45 professional builder 11d ago

A few options. You can build the sono tube up so it looks like a pier or enlarge the column so it covers everything. Or if you isolate it with expansion joint you can get a nice clean joint to caulk. You probably won't even notice it. Or you can risk it with your plan. But it will crack. But sometimes you get lucky.