Can deck posts be rested on a patio slab?

Question

In reference to the undersized concrete pier discussed in this other question:
Is the following solution a feasible one from the standpoint of distributing load over higher number of posts? (and thus minimize digging piers)
Here is what I have in mind: the ground from the house is made of concrete that extends 7ft from the house, and only then does the soil/grass start. If you look at the diagram in the first answer of the linked question, 2/3 of that ground from the ledger board is concrete (I checked the thickness and it is at least 4 inches). So my idea is to place three 4x4 posts on that concrete (at ~6ft from and parallel to the ledger board), notched to support a (2x10?) beam. The posts will be secured to brackets bolted to the concrete floor. I believe 4x4 would be adequate for the 3 posts on concrete slab.
Again, is this a sound way to decrease load from undersize posts?

isherwood · Answer

Generally speaking, floating slabs are not suitable as post footings. You're likely to see cracking under load, and if the soil underneath is unstable you'll see substantial settling.
If the question is whether it'll work in combination with your other post footings, we can only guess. It depends on the exact nature of the soil substrate, the amount and frequency of rain in your area, the total load on the posts, etc. None of us will be able to give you a better answer than what was stated in the answers to your other question.

Can deck posts be rested on a patio slab?

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