Few things look worse than crown molding hung so that it follows a wavy wall. Here in Las Vegas, a tract home selling for $750,000 will typically have walls that are serpentine 1/2" off a straight line in a 30 foot span. My procedure has been to first stretch a string along the wall from corner to corner at the crown drop and to tack shims to the wall where needed. This sometimes leaves gaps too wide for typical caulking to fill. If the customer is unwilling to have the walls floated out, what are some alternatives to this problem?
(Architectural Woodworking Forum)
From contributor A:
We ran into this situation. We first put up a strip of thin dentil molding, although you could use whatever. This was nailed tight to follow the curve. The worst bow was about 3/8", so the top of the dentil was 1/2". Well, actually, it was 3/4", but there was a 1/2" X 1/2" rabbet on the top. This gave somewhere to nail without exposing the nails. When the crown was set on top, we were able to run the crown straight because the 1/2" deep rabbet compensated for the bows. Looked great when it was done. There were no gaps along the wall and the crown was straight. Hope this at least gives some ideas.