Built-Up Cornice, Vaulted Living Room

Sample case study. Technique is accurate; the job specifics have not been verified against a real project. Replace with a real write-up and photography before launch.

The problem

A vaulted living room peaking at fourteen feet, with stock three-inch crown that had been run flat across the level sections and simply stopped where the vault began. The room had no continuous horizontal line, and at that height the profile was far too small to register anyway.

The approach

Built-up cornice rather than a larger single moulding: a backer block to carry the projection, a frieze board to add height, and a crown profile on top. That gets real scale onto a fourteen-foot wall without paying for enormous stock, and it lets each component be scribed independently where the wall is not flat.

Scale was set by sketching the elevation against the actual peak height and the existing window casings, so the cornice relates to the trim below it instead of being sized in isolation.

Construction

Backer blocks were located and fastened over framing, which also gave the scarf joints something solid to land on — a butt joint mid-bay will telegraph as the house moves.

The spring angle was checked continuously as the run went up rather than at the end. Hold it even slightly inconsistently and the profile appears to grow and shrink along the wall.

Every inside corner is cut as a tight, stable joint. On a run this visible, a mitered corner that opens up in year two would undo the whole job.