I am a drywall contractor in central Texas for 21 years. I have a builder who wants to put a colored plaster in a large home (USG Decorative Interior Finish System) over drywall (5/8 s/r tape/float/prime/plaster bond/colored plaster/sealer). My samples have been staring out or cracking-what's wrong? Is it imperative to keep a constant room temperature? Also a lot of this plaster is over a Styrofoam-type block wall system. What do I do where the s/r wall abutts to the block wall-tape with Durabond mud? Thanks for your help!