In October 2020, a tile contractor installed more than 800 square feet of tile on our southwest facing patio. We live in Oregon -- the rainy side. Shortly after install we started getting what I thought was efflorescence, a white expanding crystal that is hard to clean. The contractor re-grouted the area, but the problem not only persists, we are now getting this disgusting looking liquid coming up from the tiles. It is white pigment and contains oil. What is this and what should I do? The tile contractor says he did everything right -- he used the following:

3/6” Megalight Thin-set over a bare concrete slab (Daltile rep shared with the owner that Megalite RS should have been used)

• Daltile TS Membrane (recommended for interior but not exterior use?)

• 1/2” x 1/2” notched trowel

• Back-buttered large format tile (Emil America’s “Elegance” selected to match the large-format slate tile in the adjacent room, large format tile has a bow (warp), was set with 1/2 offsets, water pooling observed after rains, some tiles noted by the client have a hollow sound (implies not adhered) when a chain was pulled across them by the Daltile rep)

• Prism Grout (the GC said that it was sealed)

Note: The last picture is of the freshly laid tile. The large format tiles were unfortunately designed to be laid on the halves causing what you see, an uneven surface where water and debris pool. I do not know if this may exacerbate the problem.