Covering over an old brick fireplace with tile around the firebox and half inch plywood around that and the sides. Rosettes and pylasters will be nailed onto the plywood, then all the wood will be painted. We are trying to use just one layer of plywood, so we don't build out the wood too far--which would require that the distance of flammable materials--like wood--be farther away. Right now we can come within 8 inches on the sides and 12-14 inches above the firebox. While it might be easier to add another layer of plywood so that the top layer of plywood could be nailed in using finishing nails, I'm seeking a way to install that first half-inch layer of plywood with anchors or masonry nails so that the nail holes are easily coverable and so after we paint, no holes are visible. I bring this up because my contractor just suggested adding another layer to make the attachment easier, but that would I think cause problems with the plan as I've described.