Hello, and thank you for your question! This is indeed an tricky
situation and one must account for enough steel and concrete to
accommodate the weight of a person sitting on the bench. The marble we
used is 3/4" thick with a steel support pan underneath to hold the
mortar and marble in place. Then, behind the wall, we added a large structural steel beam
to account for the added weight of someone sitting on the bench.
This is what holds the bench in place and gives the appearance of a
clean edge underneath. An engineer should be able to assist you for
further development. We hope this helps, and good luck with your project!

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