I’m getting ready to pour a patio slab (roughly 18’x18′) that has the house on one side, the top of an MSE wall on 2 sides and is open on the 4th. The MSE wall is 6′ tall and capped with 4″ solid block that is glued to the blocks below. The slab will be on top of 6″ of compacted road-bond with 3″ of 3/4″ washed gravel on top of that. I have routinely pinned the concrete in similar situations, however the finishers tell me that they have been getting different, and conflicting advise from the engineers/architects on other jobs. Notably, some say that the slab should be allowed to ‘float’ so that it doesn’t tear up the wall. I was going to set pins in the block course below the cap, but am now rethinking it.

Any of you have any experience that could shed light on this?

Thanks in advance for your thoughts.