Recently installed a new bath in a pole barn with concrete floor. Have trouble with water leaching under the new tile. Plumber says it will settle and that all concrete floors have dampness under them. I am afraid of mold and odor. Any solutions?

Water should not be leaching through your tiles. There should be a moisture barrier under the slab that prevents what you are describing.

Do you have problem with ground water anyplace else in the barn ?

Not that I know of . A new trench was dug and the concrete cut out in the floor to install the drain. The water seems to be following the new trench and going under the floor, perhaps to where the cut out was left for the tub. Plumber says it will stop once it settles.