As long as the hollow clay tile wall is rigid and stable, the shotcrete application should not impact the finished side plaster. Shotcrete impacts in a very localized area directly where the material stream is hitting the substrate. Research shows that the localized force is about 90 to 100 lbs (40 to 45 kg) when shooting directly on the substrate. If shooting a thicker wall using a benching method, most of the force is carried by the previously shot material, so it would have less impact. If the clay tile needs to be stiffened, an initial thin layer could be shot to provide additional thickness before the final thickness is placed. Though we don’t have any specific information about vapor transmittal, concrete used in shotcrete placement inherently has a low w/cm and less water in the mixture to bleed or create vapor. We haven’t had any reports of plaster or grout falling off the inside of masonry walls that have been structurally enhanced with shotcrete.