What's the best way to pour post footings under a patio slab?

Question

I am looking to build footings for three 6"x6" patio cover posts which will support a 6"x8"x19ft beam for a 19ft wide x 16ft deep patio cover that will fix to my house using a ledger board.  We have an existing 4" concrete slab. Looking at the cleanest option/smallest opening for concrete footers that will support these beams.  Anchoring the bases of the posts using red head anchors.  My area calls for a 14" wide x 14" long x 12" deep footing for the post.
Should I cut out a 14 x 14" square in the concrete to dig a hole below it to fill with concrete?  Can I cut a smaller hole but dig deeper to use a concrete tube?
Appreciate any guidance.

Jasen · Answer

Cleanest is probably to use a core drill to cut a hole for the post and then use a vacuum excavator to dig the hole.
Neither step is particularly DIY
If you drill a 6" hole and then use a angle grinder with a concrete blade to enlarge it to 6" square that might be slightly neater than the 9" hole you'd otherwise need.
If there are no lateral loads on the post, you may be able to just bolt it the surface of the concrete using a post bracket

isherwood · Answer

Your question seems to be simply whether you can bell out the hole for the footing. Yes, you can. Footing specifications are for the footing structure itself, not where or how you access the space occupied by the footing. The opening in the patio would only need to be large enough for concrete to pass through, but obviously you'll need to get a post-hole digger or other tool in there as well.
You might get better answers and suggestions if updated your question post with some information about your project. Narrowly-scoped questions like this aren't terribly helpful to you or the community.

What's the best way to pour post footings under a patio slab?

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