[This is part of my How to Install Crown Molding Series.]
Buildings are designed to expand and contract with changes in temperature and humidity. And because rooms breath over the seasons, the crown moldings — if not properly installed — will separate at the joints where two piece are spliced together.
For example, the room in the image above is the lobby of one of the most sought after addresses in Birmingham, Michigan. The moldings were all professionally installed back in 2002 when the building opened.
And yet once or twice every year, the crown moldings have to be re-caulked to hide the 1/8 inch gaps that appear at all of the splices.
Above A crown molding scarf joint that’s been pushed up and over its mating piece.
Below This scarf joint (along with all of the others in the building) was filled with caulk only four months ago and yet has already separated.
Two Crown Molding Scarf Joint Tips
1. Install a three-piece crown molding instead of a single piece. Here are two posts I’ve already written that will help you get started: Why I Don’t Install One-Piece Crown Moldings and How to Install a Three-Piece Crown Molding Series.
2. Use a 45 degree miter for your scarf joint rather than a 22 degree miter. The example above shows a 22 degree miter. When glueing the two pieces together at the joint, the 45 degree miter gives you more surface area to hold the two pieces together. Also, a 45 degree scarf joint allows you to sink a few 23 gauge pins across the joint to help hold it in place.
Hope this helps you with your own crown molding installation!