Adjust upward for larger rooms.
Crown molding different ceiling heights.
Nine to 10 feet estimate crown molding width by permitting 1 2 inch of rise for each foot of ceiling height in a room with ceilings measuring 9 to 10 feet.
For standard 8 foot high ceilings the crown cornice height should be 2 to 6 inches.
The continuous header idea is an additional bridge the same height as the moulding on the 42 unit which is attached to the ceiling with the same continuous crown on it spanning across the lower 30 unit.
The height of the room as you can probably imagine the height of the ceilings in a room really play a role in whether or not crown molding is good choice.
There are of course more variations but these three examples cover the basic design aspects that you need to consider during the planning stages.
Some suggested crown mouldings for 9 foot ceilings.
Distinguished dentils photo by wendell t.
This scenario includes both ways to end a lower level crown on adjacent cabinets.
You can alter the angle to get a lesser projection with good looking results.
Webber this crown is paired with crisply milled dentil molding and beaded baseboard.
The crown moulding does not have to be at a 45 degree angle.
According to houzz this tip can come in handy for ceilings 10 feet tall or higher consider a rule of thumb allowing 1 of width for each foot of ceiling height.
These larger crowns are often built up using 2 or more moulding profiles and are also referred to as a cornice.