Q: Can you apply plaster to common drywall, or does the application of plaster require special backing such as Wonderboard?

— Thomas, Louisville, Kentucky

A: Steve Thomas replies: Wonderboard is actually a trade name for cementitious backer board, which is cement and vermiculite that's cast into sheets. It is usually used as a backing for tile, but not for veneer plaster. Veneer plaster requires a substrate of what's called blueboard, which is regular drywall with a waterproof coating (which happens to be blue). If you have drywall up presently, and you want that veneer plaster look, then I would skim the surface of the wall with drywall compound, which goes on quite easily. Use a broad knife to apply a thin coating. You can then sand it lightly, and you will get a surface that will approach that of veneer plaster. But you cannot use veneer plaster on regular drywall. It must be put over blueboard.
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