How to Add Crown Molding to Any Room

Crown molding is the architectural detail that makes a room look finished and adds a sense of quality and craftsmanship that is immediately apparent even to people who cannot identify exactly what they are responding to. It is also one of the more challenging DIY projects because it requires cutting precise compound angles — but with the right tools and technique it is achievable.

The Right Profile for Your Room

Crown molding comes in dozens of profiles ranging from simple cove molding to elaborate multi-part assemblies. In rooms with standard eight-foot ceilings, a modest molding 3.5 to 4.5 inches wide is proportionally appropriate. Larger, more elaborate profiles are for rooms with nine-foot or taller ceilings. Oversized crown on a low ceiling looks bottom-heavy and out of scale.

Coped Joints vs. Mitered Joints

At inside corners, professional trim carpenters almost always use a coped joint rather than a mitered joint. A coped joint — where one piece of molding is cut to overlap the profile of the other — accounts for the fact that most inside corners are not perfectly square. It also produces a tighter joint that holds better as the wood expands and contracts with humidity changes. Mitered joints at inside corners are faster but often open up over time.

Paint Before Installing

Prime and paint the crown molding before installation. You can touch up the nail holes and caulk lines after installation, but having the molding largely finished before it goes up significantly reduces the precision painting required on the wall and ceiling after installation. Caulk all joints and nail holes after installation, then paint the touch-ups.