Can some one please tell me what type of Marble dust and how much we should add as an aggragate to smooth stucco when applied inside a walk in shower wall? I read some earlier post about smooth stucco inside shower walls that suggested to add marble dust as an aggragate and this would make the stucco "inherently water proof" .. We have already applied the lath ,scratch coat and brown coat and later this week we plan on doing the final finish coat. We tiled the back wall of the shower pan and plan on smooth stucco for the side walls of the shower and arround the soaking tub. see photos attached and thanks in advance for help on this project. We plan on using Expo Stucco Shower coat and adding 1 lb of Marble dust per sack of stucco