I have seen pre-1900 to 1920+ or - concrete slabs "reinforced" by rib-lath
type expanded metal, laid over joists and used for both reinforcing and
I wonder if that is what you are dealing with.
Corrosion of the exposed lath is an important effect in this kind of system.
In one building, the expanded metal was corroded and peeled off the bottom
of the floor slab that it apparently was intended to reinforce, and lying on
I peek through a hole cut into the ceiling should let you see if this kind
of reinforcing is [or was] on the bottom surface of the slab.
South San Gabriel, CA
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